Subject: Re: Subduction Zone Question From: Dave Nelson davenn@............... Date: Tue, 01 Jan 2008 13:59:35 +1100 Hi Jerry, happy New Year to you too Good questions you pose ... the angle of subduction does vary a bit in different locations The SW of the South Island of New Zealand is is almost vertical under the North Island , NZ it is much shallower ~ 30deg give or take a few deg (just a couple of examples) An easy way to determine how far horizontally they go before melting is to look at what is happening at the surface .... look for ranges of volcanoes ie. the Cascades in NW USA, the central North Island, NZ, volcanoes The volcanoes of the Andes in Sth America, the strings of volcanoes along the islands of Sumatera and Java in Indonesia, the volcanic island chain of the Aleutians etc etc you get the picture :) www.sydneystormcity.com/Nth_is_x.bmp <--- a quick North Is, NZ cross-section Yellowstone is a Hot Spot (correct term) as is Hawaii they are not related to subduction they are a mantle plume that ongoing reguardless of the plate motion going on above them. Look at seabed maps of the Pacific Basin and you can see many strings of islands, atolls and seamounts that indicate past and current Hot Spot activity. A more interesting study is the depth to which the descending slab goes before it melts. and one of the deepest areas for this is in the Tonga - Kermadec Trench in the South Pacific between Fiji and New Zealand. The depth to which the slab descends is directly related to the rate of plate motion in a given region. and in the T - K Trench you get quakes regularly to in excess of 600km, but horizontally maybe only a few 10's of km (20 - 100km) away from the trench. Plate motion here is ~ 7 - 8 cm/yr and decreases as you head south from the Fiji end of the zone towards the North Is of NZ. I could go into the why's of that but thats another whole lesson in itself. The faster the plate is moving, the faster the subduction, therefore the deeper the slab will descend before it melts. Another interesting effect is in this region .... the type of quakes occurring at the great depth. Picture a subducting slab 10km thick, the norm for the seafloor. and you can imagine as it starts to subduct its cold (relativey speaking) but as it subducts it starts to heat up from the outer layers towards its centre. But because of the high speed of subduction (plate motion), the core of the slab stays cold for a very long time ie. there is very high temperature differential across the slab. This results in many tremors within the slab as it internally fractures rather than events just between the surface of the slab and the surrounding rock its grinding past. Here's a project for you ..... and you can do it for any subduction zone Plot earthquakes (from the USGS/NEIC records) on a graph showing depth Vs distance from the trench line. (ie a cross-section across the subduction zone) and it easily show you 1) .. the angle of subduction, 2) the distance from the trench the subduction zone extends. Now b4 everyone screams its already been done with Alan Jones's seismic prog, why repeat it ? yes I know it has. But to actually do the exercise yourself and plot the data from the seismicity records for a given region. It gives you a ( I believe) a better insight and understanding into the processes going on :) cheers all Dave Nelson Sydney At 02:17 AM 01/01/2008, you wrote: >Hi All, >Happy New Year. >I have a question about Subduction Zones and their angle of incidence down >to the mantle. If I remember correctly, the Mariana Trench is quite steep >while others are not. >I was wondering specifically about the Pacific and Juan de Fuca plates and >their subduction angle under the Cascade Mountains. Specifically, I am >wondering how far the subduction angel goes inland before it melts into >the mantle? >The 3.8 event at the Yellowstone Park area brought the question to >mind. I know there is supposed to be a Hot Pocket under that area and >potentially explosive, but I was wondering if the subduction wedge >extended inland that far. Truthfully, I don't know how far Yellowstone is >from the coast. > >Of course, the farther inland, the deeper the wedge would be. The >Yellowstone event was shallow (6.8 km), and obviously not what I an asking >about. Nevertheless, I was wondering about that specific area >anyway. Anybody know? > >What the heck do you have to think about anyway, New Years parties? > >Regards, >Jerry > > >No virus found in this incoming message. >Checked by AVG Free Edition. >Version: 7.5.516 / Virus Database: 269.17.12/1203 - Release Date: >12/30/2007 11:27 AM __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Subduction Zone Question From: "Jerry Payton" gpayton880@....... Date: Mon, 31 Dec 2007 21:12:21 -0600 EXCELLENT answer Dave. You have the knack of explaining that I truly appreciate. I knew my question was overly simplistic and the answer complex and different for varied locals. You did a great job, thanks. Regarding your assignment, yes that is a good way to visualize the angle. I've read paragraphs and seen drawings on just that subject. Best Wishes in 2008, Jerry
EXCELLENT answer Dave. You have the knack of explaining = that I=20 truly appreciate.  I knew my question was overly simplistic and the = answer=20 complex and different for varied locals.  You did a = great=20 job, thanks.
 
Regarding your assignment, yes that is a good way to visualize the=20 angle.  I've read paragraphs and seen drawings on just that = subject.
 
Best Wishes in 2008,
Jerry
 
Subject: First STUPID Question of the New Year? From: "Jerry Payton" gpayton880@....... Date: Tue, 1 Jan 2008 15:14:55 -0600 OK, lets start out the new year with a simple question for the group showing MY ignorance and lack of training! I fully understand the theory and principle behind the Shadow Zones, but determining what MY shadow zones would be is confusing to me. Has anyone built a windows software program to calculate what the shadow zones would be given my Lat / Long coordinates? I understand the 104-140 degree zone that used, but I cannot correlate that into a spot or spots on the globe or map. Can someone please point me in the right direction to solving this, please. (If needed, my coordinates are 36.09N 094.13W.) Jerry
OK, lets start out the new year with a simple question for the = group=20 showing MY ignorance and lack of training!
 
I fully understand the theory and principle behind the Shadow = Zones,=20 but determining what MY shadow zones would be is confusing to me.  = Has=20 anyone built a windows software program to calculate what the shadow = zones would=20 be given my Lat / Long coordinates?
 
I understand the 104-140 degree zone that used, but I cannot = correlate that=20 into a spot or spots on the globe or map.  Can someone please point = me in=20 the right direction to solving this, please.
 
(If needed, my coordinates are 36.09N  094.13W.)
 
Jerry
Subject: Re: First STUPID Question of the New Year? From: tchannel1@............ Date: Tue, 1 Jan 2008 15:52:01 -0700 Happy New Year Everyone,=20 Jerry, This might help: If you have a globe, I have a 12" dia. = globe, you could compute the two different (P wave shadow zone at = 103-143 degrees) and the (S zone at 103-180 degrees,) into inches of the = surface of your globe. For a 12" globe, one degree=3D .104 inches. = 103 degrees=3D 10.712 inches. =20 Using the appropriate length of string, place one end on your home town = and using the other end of the string you could trace or otherwise mark = its length all around the globe. This line would represent the = beginning of the 103 degree shadow zone. However, I think I saw a wed site which may do this, using your = Lat/Long, and those of the earthquake. Ted ----- Original Message -----=20 From: Jerry Payton=20 To: PSN-L=20 Sent: Tuesday, January 01, 2008 2:14 PM Subject: First STUPID Question of the New Year? OK, lets start out the new year with a simple question for the group = showing MY ignorance and lack of training! I fully understand the theory and principle behind the Shadow Zones, = but determining what MY shadow zones would be is confusing to me. Has = anyone built a windows software program to calculate what the shadow = zones would be given my Lat / Long coordinates? I understand the 104-140 degree zone that used, but I cannot correlate = that into a spot or spots on the globe or map. Can someone please point = me in the right direction to solving this, please. (If needed, my coordinates are 36.09N 094.13W.) Jerry
Happy New Year = Everyone, 
 
 Jerry,   This might=20 help:   If you have a globe, I have a 12" dia. globe, you = could=20 compute the two different (P wave shadow zone at 103-143 degrees) and=20 the (S zone at 103-180 degrees,) into inches of the surface of your = globe.    For a 12" globe, one degree=3D .104 = inches.  =20 103 degrees=3D 10.712 inches. 
Using the appropriate length of string, = place one=20 end on your home town and using the other end of the string you could = trace or=20 otherwise mark its length all around the globe.  This line would = represent=20 the beginning of the 103 degree shadow zone.
However, I think I saw a wed site which = may do=20 this, using your Lat/Long, and those of the earthquake.
Ted
----- Original Message -----
From:=20 Jerry = Payton=20
To: PSN-L
Sent: Tuesday, January 01, 2008 = 2:14=20 PM
Subject: First STUPID Question = of the New=20 Year?

OK, lets start out the new year with a simple question for the = group=20 showing MY ignorance and lack of training!
 
I fully understand the theory and principle behind the = Shadow Zones,=20 but determining what MY shadow zones would be is confusing to = me.  Has=20 anyone built a windows software program to calculate what the shadow = zones=20 would be given my Lat / Long coordinates?
 
I understand the 104-140 degree zone that used, but I cannot = correlate=20 that into a spot or spots on the globe or map.  Can someone = please point=20 me in the right direction to solving this, please.
 
(If needed, my coordinates are 36.09N  094.13W.)
 
Jerry
Subject: Re: First STUPID Question of the New Year? From: tchannel1@............ Date: Tue, 1 Jan 2008 15:52:01 -0700 Happy New Year Everyone,=20 Jerry, This might help: If you have a globe, I have a 12" dia. = globe, you could compute the two different (P wave shadow zone at = 103-143 degrees) and the (S zone at 103-180 degrees,) into inches of the = surface of your globe. For a 12" globe, one degree=3D .104 inches. = 103 degrees=3D 10.712 inches. =20 Using the appropriate length of string, place one end on your home town = and using the other end of the string you could trace or otherwise mark = its length all around the globe. This line would represent the = beginning of the 103 degree shadow zone. However, I think I saw a wed site which may do this, using your = Lat/Long, and those of the earthquake. Ted ----- Original Message -----=20 From: Jerry Payton=20 To: PSN-L=20 Sent: Tuesday, January 01, 2008 2:14 PM Subject: First STUPID Question of the New Year? OK, lets start out the new year with a simple question for the group = showing MY ignorance and lack of training! I fully understand the theory and principle behind the Shadow Zones, = but determining what MY shadow zones would be is confusing to me. Has = anyone built a windows software program to calculate what the shadow = zones would be given my Lat / Long coordinates? I understand the 104-140 degree zone that used, but I cannot correlate = that into a spot or spots on the globe or map. Can someone please point = me in the right direction to solving this, please. (If needed, my coordinates are 36.09N 094.13W.) Jerry
Happy New Year = Everyone, 
 
 Jerry,   This might=20 help:   If you have a globe, I have a 12" dia. globe, you = could=20 compute the two different (P wave shadow zone at 103-143 degrees) and=20 the (S zone at 103-180 degrees,) into inches of the surface of your = globe.    For a 12" globe, one degree=3D .104 = inches.  =20 103 degrees=3D 10.712 inches. 
Using the appropriate length of string, = place one=20 end on your home town and using the other end of the string you could = trace or=20 otherwise mark its length all around the globe.  This line would = represent=20 the beginning of the 103 degree shadow zone.
However, I think I saw a wed site which = may do=20 this, using your Lat/Long, and those of the earthquake.
Ted
----- Original Message -----
From:=20 Jerry = Payton=20
To: PSN-L
Sent: Tuesday, January 01, 2008 = 2:14=20 PM
Subject: First STUPID Question = of the New=20 Year?

OK, lets start out the new year with a simple question for the = group=20 showing MY ignorance and lack of training!
 
I fully understand the theory and principle behind the = Shadow Zones,=20 but determining what MY shadow zones would be is confusing to = me.  Has=20 anyone built a windows software program to calculate what the shadow = zones=20 would be given my Lat / Long coordinates?
 
I understand the 104-140 degree zone that used, but I cannot = correlate=20 that into a spot or spots on the globe or map.  Can someone = please point=20 me in the right direction to solving this, please.
 
(If needed, my coordinates are 36.09N  094.13W.)
 
Jerry
Subject: Re: First STUPID Question of the New Year? From: "Jerry Payton" gpayton880@....... Date: Tue, 1 Jan 2008 17:33:28 -0600 That's one of my problems. I don't have a globe of any size. And, they cost soooo much for reasonably sized globes. I assume that you determine the correct length of the string and then just "scribe" a line around the globe and everything with that area is excluded, theoretically? Jerry ----- Original Message ----- From: tchannel1@............ To: psn-l@.............. Sent: Tuesday, January 01, 2008 4:52 PM Subject: Re: First STUPID Question of the New Year? Happy New Year Everyone, Jerry, This might help: If you have a globe, I have a 12" dia. globe, you could compute the two different (P wave shadow zone at 103-143 degrees) and the (S zone at 103-180 degrees,) into inches of the surface of your globe. For a 12" globe, one degree= .104 inches. 103 degrees= 10.712 inches. Using the appropriate length of string, place one end on your home town and using the other end of the string you could trace or otherwise mark its length all around the globe. This line would represent the beginning of the 103 degree shadow zone. However, I think I saw a wed site which may do this, using your Lat/Long, and those of the earthquake. Ted ----- Original Message ----- From: Jerry Payton To: PSN-L Sent: Tuesday, January 01, 2008 2:14 PM Subject: First STUPID Question of the New Year? OK, lets start out the new year with a simple question for the group showing MY ignorance and lack of training! I fully understand the theory and principle behind the Shadow Zones, but determining what MY shadow zones would be is confusing to me. Has anyone built a windows software program to calculate what the shadow zones would be given my Lat / Long coordinates? I understand the 104-140 degree zone that used, but I cannot correlate that into a spot or spots on the globe or map. Can someone please point me in the right direction to solving this, please. (If needed, my coordinates are 36.09N 094.13W.) Jerry
That's one of my problems.  I don't have a globe of any = size. =20 And, they cost soooo much for reasonably sized globes.  I assume = that you=20 determine the correct length of the string and then just "scribe" a line = around=20 the globe and everything with that area is excluded, = theoretically?
Jerry
 
 
----- Original Message -----=20
From: tchannel1@............
To: psn-l@..............
Sent: Tuesday, January 01, 2008 4:52 PM
Subject: Re: First STUPID Question of the New = Year?

Happy New Year = Everyone, 
 
 Jerry,   This might=20 help:   If you have a globe, I have a 12" dia. globe, you = could=20 compute the two different (P wave shadow zone at 103-143 degrees) and=20 the (S zone at 103-180 degrees,) into inches of the surface of your = globe.    For a 12" globe, one degree=3D .104 = inches.  =20 103 degrees=3D 10.712 inches. 
Using the appropriate length of string, = place one=20 end on your home town and using the other end of the string you could = trace or=20 otherwise mark its length all around the globe.  This line would = represent=20 the beginning of the 103 degree shadow zone.
However, I think I saw a wed site which = may do=20 this, using your Lat/Long, and those of the earthquake.
Ted
----- Original Message -----
From:=20 Jerry = Payton=20
To: PSN-L
Sent: Tuesday, January 01, 2008 = 2:14=20 PM
Subject: First STUPID Question = of the New=20 Year?

OK, lets start out the new year with a simple question for the = group=20 showing MY ignorance and lack of training!
 
I fully understand the theory and principle behind the = Shadow Zones,=20 but determining what MY shadow zones would be is confusing to = me.  Has=20 anyone built a windows software program to calculate what the shadow = zones=20 would be given my Lat / Long coordinates?
 
I understand the 104-140 degree zone that used, but I cannot = correlate=20 that into a spot or spots on the globe or map.  Can someone = please point=20 me in the right direction to solving this, please.
 
(If needed, my coordinates are 36.09N  094.13W.)
 
Jerry
Subject: How the earth moves From: tchannel1@............ Date: Fri, 4 Jan 2008 07:08:29 -0700 Happy New Year, Folks. When I receive an earthquake, the earth and my house are moved by the = event. The various phases moves the ground in different direction. This question has to do with the movement of the earth like that of a = teeter-totter. Tilt. like that measured by a level. 1. How much does the earth move? I do understand the earth would move = in many different directions, and move more, if the earthquake was = larger, and or closer. But somewhere I think I read some numbers indicating how much the earth = would be expected to move. I am asking this question, to help me understand, the approximate tilt = from an earthquake. If I hung a one meter pendulum, and a major = earthquake occurred 1000km away, the earth here, would tilt. If I were = looking at the pendulum at the moment the S wave arrived, assuming the = sensor was pointing in the correct direction, the pendulum would appear = to tilt, but unless the event was large enough I could not see it with = my eyes. If the event was large, I would be able to see it with my eyes. I saw the earth move during an earthquake 1993? I was at my kitchen = window felt or hear something, maybe the P,looked up, and maybe 4 = seconds later, I felt a wave, one up and one down. As I was looking = outside at the time I saw the wave move down the street. If I believed = my eyes. This wave was not 12", but it must have been more than 2". Anyhow I think you get the idea. 2. Completely different question: I would like to correspond with = someone who has used both AmaSeis and WinSDR. I know AmaSeis, but = would like to get some pointers on setting up WinSDR. =20 Thanks, Ted
Happy New Year, Folks.
 
When I receive an earthquake, the earth = and my=20 house are moved by the event.  The various phases moves the ground = in=20 different direction.
This question has to do with the = movement of the=20 earth like that of a teeter-totter.  Tilt. like that measured by a=20 level.
 
1.  How much does the earth = move?  I do=20 understand the earth would move in many different directions, and move = more, if=20 the earthquake was larger, and or closer.
But somewhere I think I read some = numbers=20 indicating how much the earth would be expected to move.
 
I am asking this question, to help me = understand,=20 the approximate tilt from an earthquake.   If I hung a one = meter=20 pendulum, and a major earthquake occurred 1000km away, the earth here, = would=20 tilt.  If I were looking at the pendulum at the moment the = S wave=20 arrived, assuming the sensor was pointing in the correct direction, the = pendulum=20 would appear to tilt, but unless the event was large enough I could not = see it=20 with my eyes.
If the event was large, I would be able = to see it=20 with my eyes.
 
I saw the earth move during an=20 earthquake 1993?   I was at my kitchen window felt or = hear=20 something, maybe the P,looked up, and maybe 4 seconds later, I felt a = wave, one=20 up and one down.  As I was looking outside at the time I saw the = wave move=20 down the street.   If I believed my eyes.  This wave was = not 12",=20 but it must have been more than 2".
 
Anyhow I think you get the = idea.
 
2. Completely different question:  = I would=20 like to correspond with someone who has used both AmaSeis and=20 WinSDR.   I know AmaSeis, but would like to get some pointers = on=20 setting up WinSDR. 
 
Thanks, Ted
Subject: Burning Questions From: "Jerry Payton" gpayton880@....... Date: Fri, 4 Jan 2008 09:22:45 -0600 While everyone has their "Thinking Caps" on from Ted's excellent questions, I have a couple that have been smoldering for some time: 1) Months ago I posted an event and I received an email commenting on it. He said, "It was very good, but I might try improving my P-wave." HOW does one "improve" one phase over another? It seems that the P-wave is always less stronger. 2) Much has been written about the length of a pendulum needing to be long to be effective for teleseismic detection. However, the commercial devices are quite compact and obviously have short pendulums. Can someone explain how they accomplish what they do with short pendulums? Thank you for "thinking for me." Jerry
While everyone has their "Thinking Caps" on from Ted's excellent = questions,=20 I have a couple that have been smoldering for some time:
 
1)    Months ago I posted an event and I received an = email=20 commenting on it.  He said, "It was very good, but I = might try=20 improving my P-wave."  HOW does one "improve" one phase over = another? =20 It seems that the P-wave is always less stronger.
 
2)    Much has been written about the length of a = pendulum=20 needing to be long to be effective for teleseismic detection.  = However, the=20 commercial devices are quite compact and obviously have short = pendulums. =20 Can someone explain how they accomplish what they do with short = pendulums?
 
Thank you for "thinking for me."
Jerry
 
 
Subject: Re: Burning Questions From: ChrisAtUpw@....... Date: Fri, 4 Jan 2008 11:41:22 EST In a message dated 04/01/2008, gpayton880@....... writes: While everyone has their "Thinking Caps" on from Ted's excellent questions, I have a couple that have been smoldering for some time: 1) Months ago I posted an event and I received an email commenting on it. He said, "It was very good, but I might try improving my P-wave." HOW does one "improve" one phase over another? It seems that the P-wave is always less stronger. Hi Jerry, I suggest that you ask him? Raw data files for the relevant time interval are normally submitted. It is usual to extract the digital trace and to then apply filters to it to make the waves more visible while doing your own analysis. You might set the HP and LP filters both to 1 second when searching for teleseismic P waves, for example. 2) Much has been written about the length of a pendulum needing to be long to be effective for teleseismic detection. However, the commercial devices are quite compact and obviously have short pendulums. Can someone explain how they accomplish what they do with short pendulums? They use very low noise capacitative detectors to get the very high resolution, to maybe well below 0.1 nano metre. The period may then be extended greatly by electronic feedback, or by digital feedback, or both. They may use small pendulums with a natural period of say 0.5 second or more, but these are totally controlled by the force feedback. Because direct position and not velocity is being measured, you get a fall off in the signal below resonance of only 1/f, not 1/f^2. You can extend a 'natural' 1 second system to over 1,000 seconds, but the electronics required to do this may be quite expensive. When I receive an earthquake, the earth and my house are moved by the event. The various phases move the ground in different directions. This question has to do with the movement of the earth like that of a teeter-totter. Tilt. like that measured by a level. 1. How much does the earth move? I do understand the earth would move in many different directions, and move more, if the earthquake was larger, and or closer. But somewhere I think I read some numbers indicating how much the earth would be expected to move. If you go to _http://jclahr.com/science/psn/magnitude.html_ (http://jclahr.com/science/psn/magnitude.html) you will find several graphs and tables. Remember that surface waves are often the largest in amplitude and that their amplitude is greatly effected by the local ground type. Waterlogged alluvial ground may behave very like a jelly. I am asking this question, to help me understand, the approximate tilt from an earthquake. If I hung a one meter pendulum, and a major earthquake occurred 1000km away, the earth here, would tilt. If I were looking at the pendulum at the moment the S wave arrived, assuming the sensor was pointing in the correct direction, the pendulum would appear to tilt, but unless the event was large enough I could not see it with my eyes. You need to remember the difference in response of a pendulum to both sideways motion and to direct tilts. S waves will show lateral motion, but P and Rayleigh waves may show direct tilt effects as well as motion. Regards, Chris Chapman
In a message dated 04/01/2008, gpayton880@....... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
While everyone has their "Thinking Caps" on from Ted's excellent=20 questions, I have a couple that have been smoldering for some time:
 
1)    Months ago I posted an event and I received an e= mail=20 commenting on it.  He said, "It was very good, but I might=20= try=20 improving my P-wave."  HOW does one "improve" one phase over=20 another?  It seems that the P-wave is always less=20 stronger.
Hi Jerry,
 
    I suggest that you ask him? Raw data files for=20= the=20 relevant time interval are normally submitted.
 
    It is usual to extract the digital trace and to= =20 then apply filters to it to make the waves more visible while doing your own= =20 analysis. You might set the HP and LP filters both to 1 second when searchin= g=20 for teleseismic P waves, for example.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
2)    Much has been written about the length of a pend= ulum=20 needing to be long to be effective for teleseismic detection.  Howeve= r,=20 the commercial devices are quite compact and obviously have short=20 pendulums.  Can someone explain how they accomplish what they do with= =20 short pendulums?
    They use very low noise capacitative detectors=20= to=20 get the very high resolution, to maybe well below 0.1 nano metre. The period= may=20 then be extended greatly by electronic feedback, or by digital feedback, or=20 both. They may use small pendulums with a natural period of say 0.5 second o= r=20 more, but these are totally controlled by the force feedback. Because direct= =20 position and not velocity is being measured, you get a fall off in the signa= l=20 below resonance of only 1/f, not 1/f^2. You can extend a 'natural' 1 second=20 system to over 1,000 seconds, but the electronics required to do this may be= =20 quite expensive.
 
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
When I receive an earthquake, the earth a= nd my=20 house are moved by the event.  The various phases move the ground in=20 different directions. This question has= to do=20 with the movement of the earth like that of a teeter-totter.  Tilt. l= ike=20 that measured by a level.
 
1.  How much does the earth move?&nb= sp; I do=20 understand the earth would move in many different directions, and move mor= e,=20 if the earthquake was larger, and or closer. But somewhere I think I read some numbers indicating how much the= earth=20 would be expected to move.
    If you go to http://jclahr.com/scie= nce/psn/magnitude.html you=20 will find several graphs and tables. Remember that surface waves are often t= he=20 largest in amplitude and that their amplitude is greatly effected by the loc= al=20 ground type. Waterlogged alluvial ground may behave very like a jelly.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
I am asking this question, to help me und= erstand,=20 the approximate tilt from an earthquake.   If I hung a one meter= =20 pendulum, and a major earthquake occurred 1000km away, the earth here, wou= ld=20 tilt.  If I were looking at the pendulum at the moment the S wav= e=20 arrived, assuming the sensor was pointing in the correct direction, the=20 pendulum would appear to tilt, but unless the event was large enough I cou= ld=20 not see it with my eyes.
    You need to remember the difference in response= of=20 a pendulum to both sideways motion and to direct tilts. S waves will show=20 lateral motion,  but P and Rayleigh waves may show direct tilt effects=20= as=20 well as motion.
 
    Regards,
 
    Chris Chapman
Subject: Hekla volcano geophone planned From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Fri, 04 Jan 2008 17:03:55 +0000 Hi all I am going to setup a geophone close to the Hekla volcano this year (20 something km). I am going to speed up progress of setting up that geophone as I can, but at the latest the geophone is going up next summer. Hekla volcano is ready to erupt at any time. That is the reason for the speedup for that project. Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: "Jerry Payton" gpayton880@....... Date: Fri, 4 Jan 2008 11:07:42 -0600 Jon, how in the world are you linking to all these geophones and back to your station?? 20 something km !!!??? Jerry ----- Original Message ----- From: Jón Frímann To: PSN-Postlist Sent: Friday, January 04, 2008 11:03 AM Subject: Hekla volcano geophone planned Hi all I am going to setup a geophone close to the Hekla volcano this year (20 something km). I am going to speed up progress of setting up that geophone as I can, but at the latest the geophone is going up next summer. Hekla volcano is ready to erupt at any time. That is the reason for the speedup for that project. Regards. -- Jón Frímann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Jon, how in the world are you linking to all these geophones = and=20  back to your station?? 20 something km !!!???
Jerry
 
 
----- Original Message -----=20
From: J=F3n = Fr=EDmann
To: PSN-Postlist
Sent: Friday, January 04, 2008 11:03 AM
Subject: Hekla volcano geophone planned

Hi all

I am going to setup a geophone close to the = Hekla=20 volcano this year (20
something km). I am going to speed up progress = of=20 setting up that
geophone as I can, but at the latest the geophone is = going up=20 next
summer.

Hekla volcano is ready to erupt at any time. That = is the=20 reason for the
speedup for that project.

Regards.
-- =
J=F3n=20 Fr=EDmann
http://www.jonfr.com
http://earthquakes.jonfr.comhttp://www.net303.net
http://www.mobile-coverage.com/<= /A>

__________________________________________________________
=
Public=20 Seismic Network Mailing List (PSN-L)

To leave this list email PSN-L-REQUEST@............... with=20
the body of the message (first line only): unsubscribe
See http://www.seismicnet.co= m/maillist.html=20 for more information.
Subject: Re: Hekla volcano geophone planned From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Fri, 04 Jan 2008 17:10:47 +0000 Hi The geophone is going to be located at a house that is ~20 km away from Hekla volcano. But the connection from there to my main computer I am going to use the internet. Regards.=20 --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: "Jerry Payton" gpayton880@....... Date: Fri, 4 Jan 2008 11:17:19 -0600 Hmmmm That's interesting, Jon. I'd like to know more how you accomplish that without a different IP address for each geophone that you use. You might contact me directly gpayton880@....... with an explanation and/or drawing when you have time. Regards, Jerry ----- Original Message ----- From: Jón Frímann To: psn-l@.............. Sent: Friday, January 04, 2008 11:10 AM Subject: Re: Hekla volcano geophone planned Hi The geophone is going to be located at a house that is ~20 km away from Hekla volcano. But the connection from there to my main computer I am going to use the internet. Regards. -- Jón Frímann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Hmmmm  That's interesting, Jon.  I'd like to know more = how you=20 accomplish that without a different IP address for each geophone that = you=20 use.  You might contact me directly  gpayton880@.......  with an=20 explanation and/or drawing when you have time.
Regards,
Jerry
 
 
----- Original Message -----=20
From: J=F3n = Fr=EDmann
Sent: Friday, January 04, 2008 11:10 AM
Subject: Re: Hekla volcano geophone planned

Hi

The geophone is going to be located at a house = that is=20 ~20 km away from
Hekla volcano. But the connection from there to my = main=20 computer I am
going to use the internet.

Regards.
-- =
J=F3n=20 Fr=EDmann
http://www.jonfr.com
http://earthquakes.jonfr.comhttp://www.net303.net
http://www.mobile-coverage.com/<= /A>

__________________________________________________________
=
Public=20 Seismic Network Mailing List (PSN-L)

To leave this list email PSN-L-REQUEST@............... with=20
the body of the message (first line only): unsubscribe
See http://www.seismicnet.co= m/maillist.html=20 for more information.
Subject: RE: Hekla volcano geophone planned From: "Timothy Carpenter" geodynamics@....... Date: Fri, 4 Jan 2008 13:24:03 -0500 Jon & Jerry, I too would be interested in how you are setting up your internet connection(s) =96 so let=92s keep the discussion on-list. -Tim- Timothy Carpenter =20 From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Jerry Payton Sent: Friday, January 04, 2008 12:17 PM To: psn-l@.............. Subject: Re: Hekla volcano geophone planned =20 Hmmmm That's interesting, Jon. I'd like to know more how you = accomplish that without a different IP address for each geophone that you use. You might contact me directly gpayton880@....... with an explanation = and/or drawing when you have time. Regards, Jerry =20 =20 ----- Original Message -----=20 From: J=F3n Fr=EDmann =20 To: psn-l@................. Sent: Friday, January 04, 2008 11:10 AM Subject: Re: Hekla volcano geophone planned =20 Hi The geophone is going to be located at a house that is ~20 km away from Hekla volcano. But the connection from there to my main computer I am going to use the internet. Regards.=20 --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L)

Jon & Jerry,

I too would be interested in how you are setting up your internet connection(s) – so let’s keep the discussion = on-list.

-Tim-

Timothy Carpenter

 

From:= psn-l-request@.............. [mailto:psn-l-request@............... On = Behalf Of Jerry Payton
Sent: Friday, January 04, 2008 12:17 PM
To: psn-l@..............
Subject: Re: Hekla volcano geophone planned

 

Hmmmm  That's interesting, Jon.  I'd like = to know more how you accomplish that without a different IP address for each = geophone that you use.  You might contact me directly  gpayton880@.......  with an explanation and/or drawing when you have time.

Regards,

Jerry

 

 

----- Original Message -----

Sent:<= /b> Friday, = January 04, 2008 11:10 AM

Subject: Re: Hekla = volcano geophone planned

 

Hi

The geophone is going to be located at a house that is ~20 km away = from
Hekla volcano. But the connection from there to my main computer I = am
going to use the internet.

Regards.
--
J=F3n Fr=EDmann
http://www.jonfr.com
http://earthquakes.jonfr.com http://www.net303.net
http://www.mobile-coverage.com/<= /a>

__________________________________________________________

Public Seismic Network Mailing List (PSN-L)

To leave this list email PSN-L-REQUEST@............... with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.co= m/maillist.html for more information.

Subject: RE: Hekla volcano geophone planned From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Fri, 04 Jan 2008 18:45:23 +0000 Hi I have a pc with each geophone. The internet is used to send me the data back to my main computer. It looks like this, Main PC (hvt station) --- Internet --- Hekla geophone+pc I try to use the internet connection that already there, rather then have to buy one on my own. I have used this type of setup already. The Mosfellsb=E6r station is connecteted in this way already. Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Fri, 04 Jan 2008 20:28:53 +0000 Hi, to answer the question below, more than 1 data source per ip address, here's 2 approaches (many more no doubt are possible): tcp/ip sockets. Using these, each ip address can be split into 65536 channels, or sockets, 0 to 65535. Some of these are already allocated, like 25 for mail and 80 for web browsing. Anything above 1000 should be available but check or be alert to something no longer working and try another socket number. These are also what those nasty hacker creatures use for sneaking into unprotected pcs. You could have 1 socket per sensor. Under this regime you would need to have a server program running in the pc for each socket. It "listens" for incoming connections. When a connection request is made, it starts serving up the stream of data for that particular sensor. But rather than have 1 sensor on a single socket it is more sensible to have many sensors on a single socket using a data protocol. This is how I have designed my system. It sends out a continuous stream (50 samples per second) of "(Lehman reading) (geophone reading) (time stamp)". My graphing program makes a connection to the "data server" and plots the values from the 2 sensors as they arrive. See http://www.iasmith.com. As you'll see, my above-ground system is badly affected by wind. I recently achieved a big increase in sensitivity and was rewarded by the now increased significance of the wind :-( . I need to dig down and make a below-ground system. Segway to the next topic... Cheers Ian Jerry Payton wrote: > Hmmmm That's interesting, Jon. I'd like to know more how you > accomplish that without a different IP address for each geophone that > you use. You might contact me directly gpayton880@....... > with an explanation and/or drawing when > you have time. > Regards, > Jerry > > > ----- Original Message ----- > *From:* Jón Frímann > *To:* psn-l@.............. > *Sent:* Friday, January 04, 2008 11:10 AM > *Subject:* Re: Hekla volcano geophone planned > > Hi > > The geophone is going to be located at a house that is ~20 km away from > Hekla volcano. But the connection from there to my main computer I am > going to use the internet. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://earthquakes.jonfr.com > http://www.net303.net > http://www.mobile-coverage.com/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. > with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: "Jerry Payton" gpayton880@....... Date: Fri, 4 Jan 2008 15:48:56 -0600 Thank you Ian, Jon and Tim, All good answers. When I heard something new to me, my mind says, "Hmmm. Wonder how that works or how that is hooked up." I appreciate each input. Jerry ----- Original Message ----- From: ian To: psn-l@.............. Sent: Friday, January 04, 2008 2:28 PM Subject: Re: Hekla volcano geophone planned Hi, to answer the question below, more than 1 data source per ip address, here's 2 approaches (many more no doubt are possible): tcp/ip sockets. Using these, each ip address can be split into 65536 channels, or sockets, 0 to 65535. Some of these are already allocated, like 25 for mail and 80 for web browsing. Anything above 1000 should be available but check or be alert to something no longer working and try another socket number. These are also what those nasty hacker creatures use for sneaking into unprotected pcs. You could have 1 socket per sensor. Under this regime you would need to have a server program running in the pc for each socket. It "listens" for incoming connections. When a connection request is made, it starts serving up the stream of data for that particular sensor. But rather than have 1 sensor on a single socket it is more sensible to have many sensors on a single socket using a data protocol. This is how I have designed my system. It sends out a continuous stream (50 samples per second) of "(Lehman reading) (geophone reading) (time stamp)". My graphing program makes a connection to the "data server" and plots the values from the 2 sensors as they arrive. See http://www.iasmith.com. As you'll see, my above-ground system is badly affected by wind. I recently achieved a big increase in sensitivity and was rewarded by the now increased significance of the wind :-( . I need to dig down and make a below-ground system. Segway to the next topic... Cheers Ian Jerry Payton wrote: > Hmmmm That's interesting, Jon. I'd like to know more how you > accomplish that without a different IP address for each geophone that > you use. You might contact me directly gpayton880@....... > with an explanation and/or drawing when > you have time. > Regards, > Jerry > > > ----- Original Message ----- > *From:* Jón Frímann > *To:* psn-l@.............. > *Sent:* Friday, January 04, 2008 11:10 AM > *Subject:* Re: Hekla volcano geophone planned > > Hi > > The geophone is going to be located at a house that is ~20 km away from > Hekla volcano. But the connection from there to my main computer I am > going to use the internet. > > Regards. > -- > Jón Frímann > http://www.jonfr.com > http://earthquakes.jonfr.com > http://www.net303.net > http://www.mobile-coverage.com/ > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. > with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Thank you Ian, Jon and Tim,
 
All good answers.  When I heard something new to me, my mind = says,=20 "Hmmm. Wonder how that works or how that is hooked up."  I = appreciate each=20 input.
Jerry
 
 
----- Original Message -----=20
From: ian
Sent: Friday, January 04, 2008 2:28 PM
Subject: Re: Hekla volcano geophone planned

Hi,

to answer the question below, more than 1 data = source=20 per ip address,
here's 2 approaches (many more no doubt are=20 possible):

tcp/ip sockets.  Using these, each ip address can = be=20 split into 65536
channels, or sockets, 0 to 65535.  Some of = these are=20 already allocated,
like 25 for mail and 80 for web browsing.  = Anything=20 above 1000 should be
available but check or be alert to something no = longer=20 working and try
another socket number.  These are also what = those nasty=20 hacker creatures
use for sneaking into unprotected pcs.

You = could=20 have 1 socket per sensor.  Under this regime you would need to =
have a=20 server program running in the pc for each socket.  It "listens" =
for=20 incoming connections.  When a connection request is made, it starts =
serving up the stream of data for that particular sensor.

But = rather=20 than have 1 sensor on a single socket it is more sensible to
have = many=20 sensors on a single socket using a data protocol.  This is how =
I have=20 designed my system.  It sends out a continuous stream (50 samples =
per=20 second) of "(Lehman reading) (geophone reading) (time stamp)".  My=20
graphing program makes a connection to the "data server" and plots = the=20
values from the 2 sensors as they arrive.  See http://www.iasmith.com.

As = you'll see,=20 my above-ground system is badly affected by wind.  I
recently = achieved=20 a big increase in sensitivity and was rewarded by the
now increased=20 significance of the wind  :-( .  I need to dig down and =
make a=20 below-ground system.  Segway to the next=20 topic...

Cheers

Ian



Jerry Payton = wrote:
>=20 Hmmmm  That's interesting, Jon.  I'd like to know more how you =
> accomplish that without a different IP address for each = geophone that=20
> you use.  You might contact me directly  gpayton880@.......
> = <mailto:gpayton880@.......> = ; with an=20 explanation and/or drawing when
> you have time.
> = Regards,
>=20 Jerry
> 
> 
> ----- Original Message = -----
>=20 *From:* J=F3n Fr=EDmann <mailto:jonfr@.........>
> = *To:* psn-l@.............. <mailto:psn-l@..............><= BR>>=20 *Sent:* Friday, January 04, 2008 11:10 AM
> *Subject:* Re: Hekla = volcano=20 geophone planned
>
> Hi
>
> The geophone is = going to be=20 located at a house that is ~20 km away from
> Hekla volcano. But = the=20 connection from there to my main computer I am
> going to use the=20 internet.
>
> Regards.
> --
> J=F3n = Fr=EDmann
> http://www.jonfr.com
> http://earthquakes.jonfr.com> http://www.net303.net
> http://www.mobile-coverage.com/<= /A>
>
>=20 __________________________________________________________
>
>= ;=20 Public Seismic Network Mailing List (PSN-L)
>
> To leave = this list=20 email PSN-L-REQUEST@............... =20
> <mailto:PSN-L-REQUEST@SEISMIC= NET.COM>=20 with
> the body of the message (first line only): = unsubscribe
> See=20 http://www.seismicnet.co= m/maillist.html=20 for more information.

--

<http://www.festivalpreviews.com<= /A>>
__________________________________________________________
=
Public=20 Seismic Network Mailing List (PSN-L)

To leave this list email PSN-L-REQUEST@............... with=20
the body of the message (first line only): unsubscribe
See http://www.seismicnet.co= m/maillist.html=20 for more information.
Subject: Re: Hekla volcano geophone planned From: ChrisAtUpw@....... Date: Sat, 5 Jan 2008 00:20:26 EST In a message dated 04/01/2008, gpayton880@....... writes: But rather than have 1 sensor on a single socket it is more sensible to have many sensors on a single socket using a data protocol. This is how I have designed my system. It sends out a continuous stream (50 samples per second) of "(Lehman reading) (geophone reading) (time stamp)". My graphing program makes a connection to the "data server" and plots the values from the 2 sensors as they arrive. See _http://www.iasmith.com_ (http://www.iasmith.com/) . Hi Ian, The limitation tends to be the total data throughput speed reqired. 50 SPS is quite fast. The ADC sample rate can also impose limitations. This starts to become serious when you have, say several three off three channel sensors on the same ADC. Regards, Chris Chapman
In a message dated 04/01/2008, gpayton880@....... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>But=20 rather than have 1 sensor on a single socket it is more sensible to
ha= ve=20 many sensors on a single socket using a data protocol.  This is how <= BR>I=20 have designed my system.  It sends out a continuous stream (50 sample= s=20
per second) of "(Lehman reading) (geophone reading) (time stamp)".&nbs= p;=20 My
graphing program makes a connection to the "data server" and plots=20= the=20
values from the 2 sensors as they arrive.  See http://www.iasmith.com.
Hi Ian,
 
    The limitation tends to be the total data=20 throughput speed reqired. 50 SPS is quite fast. The ADC sample rate can= =20 also impose limitations. This starts to become serious when you have, say=20 several three off three channel sensors on the same ADC.
 
    Regards,
 
    Chris Chapman
Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Sat, 05 Jan 2008 09:35:41 +0000 Hi, actually, I don't think I'm near any limits. The A/D I use can handle 20K samples/sec. I only have 2 instruments (though I sample each on 3 A/D channels to get the resolution up to 22 bits), so that's only 6 x 50, or 300 samples/sec. So I could connect up all of the A/D's 16 input channels and still not stress it. The data server does burn up 80% of the PC's CPU but it's only an old 800 MHz machine and wouldn't cost much to replace with one twice the speed. Data across the network connection is only 32 characters x 50 or 1600 bytes/sec. Less than a 500th of the 100 Mb/s network bandwidth (being generous). All of the above though, implies that you are happy to write your own code. Buying building blocks off the shelf can be very attractive. For multiple instruments you could buy several PSN A/D boards. To overcome the potential problem of connecting up multiple RS232 cables, you could use a network terminal server (such as http://www.perle.com/products/IOLAN-STS-Terminal-Server.shtml?rack ). These aggregate up to 4/8/16/24 rs232 connections on to one network connection. They usually come with software for the pc which creates multiple virtual COM ports, so your A/D boards would look like they are plugged into an array of COM ports on the PC. Isn't technology wonderful! Cheers Ian ChrisAtUpw@....... wrote: > In a message dated 04/01/2008, gpayton880@....... writes: > > But rather than have 1 sensor on a single socket it is more > sensible to > have many sensors on a single socket using a data protocol. This > is how > I have designed my system. It sends out a continuous stream (50 > samples > per second) of "(Lehman reading) (geophone reading) (time > stamp)". My > graphing program makes a connection to the "data server" and plots > the > values from the 2 sensors as they arrive. See > http://www.iasmith.com . > > Hi Ian, > > The limitation tends to be the total data throughput > speed reqired. 50 SPS is quite fast. The ADC sample rate can also > impose limitations. This starts to become serious when you have, say > several three off three channel sensors on the same ADC. > > Regards, > > Chris Chapman -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Sat, 05 Jan 2008 11:28:55 +0000 Hi All of my remote sensors are going to be connected over the internet. I have ~6mb ADSL connection, so it should be able to handle it. The data flow isn't a lot, about ~100mb pr day on each station. Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Large earthquake near cost of Canada From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Sat, 05 Jan 2008 11:32:14 +0000 Hi all There appears to have been a large earthquake near the cost of Canada this morning (GMT time). I am unsure what the size is, but usgs is reporting M6.5 Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: ian ian@........... Date: Sat, 05 Jan 2008 11:44:53 +0000 Hi, yes thanks, I can see it. It's a bit windy here, so my trace is not pristine... Cheers Ian http://www.iasmith.com http://www.festivalpreviews.com Jón Frímann wrote: > Hi all > > There appears to have been a large earthquake near the cost of Canada > this morning (GMT time). I am unsure what the size is, but usgs is > reporting M6.5 > > Regards. > -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Sat, 05 Jan 2008 12:15:43 +0000 Hi At 11:44 GMT there was a second large earthquake near the east cost of Canada, USGS early size gives it M6.5. This is quite unusual for this area to have two earthquakes with this short period. Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re[2]: Hekla volcano geophone planned From: Angel sismos@.............. Date: Sat, 5 Jan 2008 13:57:23 +0000 Hello Jon, Timothy and all, I would like this thread on the list also. Angel Friday, January 4, 2008, 6:24:03 PM, you wrote: > Jon & Jerry, > I too would be interested in how you are setting up your internet > connection(s) – so let’s keep the discussion on-list. > -Tim- > Timothy Carpenter > > From: psn-l-request@.............. > [mailto:psn-l-request@............... On Behalf Of Jerry Payton > Sent: Friday, January 04, 2008 12:17 PM > To: psn-l@.............. > Subject: Re: Hekla volcano geophone planned > > Hmmmm That's interesting, Jon. I'd like to know more how you > accomplish that without a different IP address for each geophone > that you use. You might contact me directly gpayton880@....... > with an explanation and/or drawing when you have time. > Regards, > Jerry > > > ----- Original Message ----- > From: Jón Frímann > To: psn-l@.............. > Sent: Friday, January 04, 2008 11:10 AM > Subject: Re: Hekla volcano geophone planned > > Hi > The geophone is going to be located at a house that is ~20 km away from > Hekla volcano. But the connection from there to my main computer I am > going to use the internet. > Regards. -- Best regards, Angel __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Burning Questions From: Brett Nordgren Brett3mr@............. Date: Sat, 05 Jan 2008 10:12:06 -0500 Jerry, re: 2) Almost all modern commercial sensors use some form of an astatic leaf-spring suspension. See fig. 10 of http://jclahr.com/science/psn/wielandt/node15.html With careful design and very careful adjustment, even quite a small pendulum (2") can be made to have a long free period. However, such a setup is very prone to drift from temperature and other changes and is only useful when it is combined with feedback such as Chris describes, to broaden its frequency response curve and stabilize its tendency to 'wander'. In such an instrument the real benefit of the long free period is to make it easier for the feedback to accurately control its motion. Long free period = low restoring force = less feedback force needed to control the pendulum. Brett At 09:22 AM 1/4/2008 -0600, you wrote: >While everyone has their "Thinking Caps" on from Ted's excellent >questions, I have a couple that have been smoldering for some time: > >1) Months ago I posted an event and I received an email commenting on >it. He said, "It was very good, but I might try improving my >P-wave." HOW does one "improve" one phase over another? It seems that >the P-wave is always less stronger. > >2) Much has been written about the length of a pendulum needing to be >long to be effective for teleseismic detection. However, the commercial >devices are quite compact and obviously have short pendulums. Can someone >explain how they accomplish what they do with short pendulums? > >Thank you for "thinking for me." >Jerry My e-mail address above should be working, but if not you can always use my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re[2]: Hekla volcano geophone planned From: Angel sismos@.............. Date: Sat, 5 Jan 2008 15:39:15 +0000 Hello Ian, I have not read each messages of this thread careful but I will. All of the software needed to link a large distributed seismic system is free and freely available. Anyone who has one of Larry's 16 bit 8 channel boards with GPS (wwv) timing and a full time internet connection can share data and PSN can a global or regional system auto locating system. Angel Saturday, January 5, 2008, 9:35:41 AM, you wrote: > Hi, > actually, I don't think I'm near any limits. The A/D I use can handle > 20K samples/sec. I only have 2 instruments (though I sample each on 3 > A/D channels to get the resolution up to 22 bits), so that's only 6 x > 50, or 300 samples/sec. So I could connect up all of the A/D's 16 input > channels and still not stress it. > The data server does burn up 80% of the PC's CPU but it's only an old > 800 MHz machine and wouldn't cost much to replace with one twice the > speed. Data across the network connection is only 32 characters x 50 or > 1600 bytes/sec. Less than a 500th of the 100 Mb/s network bandwidth > (being generous). > All of the above though, implies that you are happy to write your own > code. Buying building blocks off the shelf can be very attractive. For > multiple instruments you could buy several PSN A/D boards. To overcome > the potential problem of connecting up multiple RS232 cables, you could > use a network terminal server (such as > http://www.perle.com/products/IOLAN-STS-Terminal-Server.shtml?rack ). > These aggregate up to 4/8/16/24 rs232 connections on to one network > connection. They usually come with software for the pc which creates > multiple virtual COM ports, so your A/D boards would look like they are > plugged into an array of COM ports on the PC. > Isn't technology wonderful! > Cheers > Ian > ChrisAtUpw@....... wrote: >> In a message dated 04/01/2008, gpayton880@....... writes: >> But rather than have 1 sensor on a single socket it is more >> sensible to >> have many sensors on a single socket using a data protocol. This >> is how >> I have designed my system. It sends out a continuous stream (50 >> samples >> per second) of "(Lehman reading) (geophone reading) (time >> stamp)". My >> graphing program makes a connection to the "data server" and plots >> the >> values from the 2 sensors as they arrive. See >> http://www.iasmith.com . >> Hi Ian, >> >> The limitation tends to be the total data throughput >> speed reqired. 50 SPS is quite fast. The ADC sample rate can also >> impose limitations. This starts to become serious when you have, say >> several three off three channel sensors on the same ADC. >> >> Regards, >> >> Chris Chapman -- Best regards, Angel __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Sat, 05 Jan 2008 15:57:40 +0000 Hi, yes, you're right, all free. I was really addressing the earlier (possibly hypothetical) question of how to connect many sensors to 1 network connection. The engineer in me probably made my response a bit enthusiastic and suitable for connecting dozens of sensors. Back to (free) reality! Cheers Ian http://www.iasmith.com/ http://www.festivalpreviews.com Angel wrote: > Hello Ian, > > I have not read each messages of this thread careful but I will. All of the software needed to link a large distributed seismic system is free and freely available. > > Anyone who has one of Larry's 16 bit 8 channel boards with GPS (wwv) timing and a full time internet connection can share data and PSN can a global or regional system auto locating system. > > Angel > > > > Saturday, January 5, 2008, 9:35:41 AM, you wrote: > > >> Hi, >> > > >> actually, I don't think I'm near any limits. The A/D I use can handle >> 20K samples/sec. I only have 2 instruments (though I sample each on 3 >> A/D channels to get the resolution up to 22 bits), so that's only 6 x >> 50, or 300 samples/sec. So I could connect up all of the A/D's 16 input >> channels and still not stress it. >> > > >> The data server does burn up 80% of the PC's CPU but it's only an old >> 800 MHz machine and wouldn't cost much to replace with one twice the >> speed. Data across the network connection is only 32 characters x 50 or >> 1600 bytes/sec. Less than a 500th of the 100 Mb/s network bandwidth >> (being generous). >> > > >> All of the above though, implies that you are happy to write your own >> code. Buying building blocks off the shelf can be very attractive. For >> multiple instruments you could buy several PSN A/D boards. To overcome >> the potential problem of connecting up multiple RS232 cables, you could >> use a network terminal server (such as >> http://www.perle.com/products/IOLAN-STS-Terminal-Server.shtml?rack ). >> These aggregate up to 4/8/16/24 rs232 connections on to one network >> connection. They usually come with software for the pc which creates >> multiple virtual COM ports, so your A/D boards would look like they are >> plugged into an array of COM ports on the PC. >> > > >> Isn't technology wonderful! >> > > >> Cheers >> > > >> Ian >> > > >> ChrisAtUpw@....... wrote: >> >>> In a message dated 04/01/2008, gpayton880@....... writes: >>> > > >>> But rather than have 1 sensor on a single socket it is more >>> sensible to >>> have many sensors on a single socket using a data protocol. This >>> is how >>> I have designed my system. It sends out a continuous stream (50 >>> samples >>> per second) of "(Lehman reading) (geophone reading) (time >>> stamp)". My >>> graphing program makes a connection to the "data server" and plots >>> the >>> values from the 2 sensors as they arrive. See >>> http://www.iasmith.com . >>> > > >>> Hi Ian, >>> >>> The limitation tends to be the total data throughput >>> speed reqired. 50 SPS is quite fast. The ADC sample rate can also >>> impose limitations. This starts to become serious when you have, say >>> several three off three channel sensors on the same ADC. >>> >>> Regards, >>> >>> Chris Chapman >>> > > > > > -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re[2]: Hekla volcano geophone planned From: Angel sismos@.............. Date: Sat, 5 Jan 2008 16:13:08 +0000 Hello Ian, Just to get an idea, how many PSN-ADC-SERIAL Version II with GPS timing and full time internet connection are there out there. I have one. Angel Saturday, January 5, 2008, 3:57:40 PM, you wrote: > Hi, > yes, you're right, all free. I was really addressing the earlier > (possibly hypothetical) question of how to connect many sensors to 1 > network connection. The engineer in me probably made my response a bit > enthusiastic and suitable for connecting dozens of sensors. > Back to (free) reality! > Cheers > Ian > http://www.iasmith.com/ > http://www.festivalpreviews.com > Angel wrote: >> Hello Ian, >> I have not read each messages of this thread careful but I will. All of the software needed to link a large distributed seismic system is free and freely available. >> Anyone who has one of Larry's 16 bit 8 channel boards with GPS (wwv) timing and a full time internet connection can share data and PSN can a global or regional system auto locating system. >> Angel >> Saturday, January 5, 2008, 9:35:41 AM, you wrote: >> >>> Hi, >>> >> >>> actually, I don't think I'm near any limits. The A/D I use can handle >>> 20K samples/sec. I only have 2 instruments (though I sample each on 3 >>> A/D channels to get the resolution up to 22 bits), so that's only 6 x >>> 50, or 300 samples/sec. So I could connect up all of the A/D's 16 input >>> channels and still not stress it. >>> >> >>> The data server does burn up 80% of the PC's CPU but it's only an old >>> 800 MHz machine and wouldn't cost much to replace with one twice the >>> speed. Data across the network connection is only 32 characters x 50 or >>> 1600 bytes/sec. Less than a 500th of the 100 Mb/s network bandwidth >>> (being generous). >>> >> >>> All of the above though, implies that you are happy to write your own >>> code. Buying building blocks off the shelf can be very attractive. For >>> multiple instruments you could buy several PSN A/D boards. To overcome >>> the potential problem of connecting up multiple RS232 cables, you could >>> use a network terminal server (such as >>> http://www.perle.com/products/IOLAN-STS-Terminal-Server.shtml?rack ). >>> These aggregate up to 4/8/16/24 rs232 connections on to one network >>> connection. They usually come with software for the pc which creates >>> multiple virtual COM ports, so your A/D boards would look like they are >>> plugged into an array of COM ports on the PC. >>> >> >>> Isn't technology wonderful! >>> >> >>> Cheers >>> >> >>> Ian >>> >> >>> ChrisAtUpw@....... wrote: >>> >>>> In a message dated 04/01/2008, gpayton880@....... writes: >>>> >> >>>> But rather than have 1 sensor on a single socket it is more >>>> sensible to >>>> have many sensors on a single socket using a data protocol. This >>>> is how >>>> I have designed my system. It sends out a continuous stream (50 >>>> samples >>>> per second) of "(Lehman reading) (geophone reading) (time >>>> stamp)". My >>>> graphing program makes a connection to the "data server" and plots >>>> the >>>> values from the 2 sensors as they arrive. See >>>> http://www.iasmith.com . >>>> >> >>>> Hi Ian, >>>> >>>> The limitation tends to be the total data throughput >>>> speed reqired. 50 SPS is quite fast. The ADC sample rate can also >>>> impose limitations. This starts to become serious when you have, say >>>> several three off three channel sensors on the same ADC. >>>> >>>> Regards, >>>> >>>> Chris Chapman >>>> >> -- Best regards, Angel __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Sat, 05 Jan 2008 16:24:56 +0000 Hi, I don't know. I don't have one. Presumably an approximation can be got from http://www.sydneystormcity.com/people.htm Cheers Ian Angel wrote: > Hello Ian, > > Just to get an idea, how many PSN-ADC-SERIAL Version II with GPS timing and full time internet connection are there out there. > > I have one. > > Angel > > Saturday, January 5, 2008, 3:57:40 PM, you wrote: > > >> Hi, >> > > >> yes, you're right, all free. I was really addressing the earlier >> (possibly hypothetical) question of how to connect many sensors to 1 >> network connection. The engineer in me probably made my response a bit >> enthusiastic and suitable for connecting dozens of sensors. >> > > >> Back to (free) reality! >> > > >> Cheers >> > > >> Ian >> http://www.iasmith.com/ >> http://www.festivalpreviews.com >> > > >> Angel wrote: >> >>> Hello Ian, >>> > > >>> I have not read each messages of this thread careful but I will. All of the software needed to link a large distributed seismic system is free and freely available. >>> > > >>> Anyone who has one of Larry's 16 bit 8 channel boards with GPS (wwv) timing and a full time internet connection can share data and PSN can a global or regional system auto locating system. >>> > > >>> Angel >>> > > > > >>> Saturday, January 5, 2008, 9:35:41 AM, you wrote: >>> > > >>> >>> >>>> Hi, >>>> >>>> > > >>> >>> >>>> actually, I don't think I'm near any limits. The A/D I use can handle >>>> 20K samples/sec. I only have 2 instruments (though I sample each on 3 >>>> A/D channels to get the resolution up to 22 bits), so that's only 6 x >>>> 50, or 300 samples/sec. So I could connect up all of the A/D's 16 input >>>> channels and still not stress it. >>>> >>>> > > >>> >>> >>>> The data server does burn up 80% of the PC's CPU but it's only an old >>>> 800 MHz machine and wouldn't cost much to replace with one twice the >>>> speed. Data across the network connection is only 32 characters x 50 or >>>> 1600 bytes/sec. Less than a 500th of the 100 Mb/s network bandwidth >>>> (being generous). >>>> >>>> > > >>> >>> >>>> All of the above though, implies that you are happy to write your own >>>> code. Buying building blocks off the shelf can be very attractive. For >>>> multiple instruments you could buy several PSN A/D boards. To overcome >>>> the potential problem of connecting up multiple RS232 cables, you could >>>> use a network terminal server (such as >>>> http://www.perle.com/products/IOLAN-STS-Terminal-Server.shtml?rack ). >>>> These aggregate up to 4/8/16/24 rs232 connections on to one network >>>> connection. They usually come with software for the pc which creates >>>> multiple virtual COM ports, so your A/D boards would look like they are >>>> plugged into an array of COM ports on the PC. >>>> >>>> > > >>> >>> >>>> Isn't technology wonderful! >>>> >>>> > > >>> >>> >>>> Cheers >>>> >>>> > > >>> >>> >>>> Ian >>>> >>>> > > >>> >>> >>>> ChrisAtUpw@....... wrote: >>>> >>>> >>>>> In a message dated 04/01/2008, gpayton880@....... writes: >>>>> >>>>> > > >>> >>> >>>>> But rather than have 1 sensor on a single socket it is more >>>>> sensible to >>>>> have many sensors on a single socket using a data protocol. This >>>>> is how >>>>> I have designed my system. It sends out a continuous stream (50 >>>>> samples >>>>> per second) of "(Lehman reading) (geophone reading) (time >>>>> stamp)". My >>>>> graphing program makes a connection to the "data server" and plots >>>>> the >>>>> values from the 2 sensors as they arrive. See >>>>> http://www.iasmith.com . >>>>> >>>>> > > >>> >>> >>>>> Hi Ian, >>>>> >>>>> The limitation tends to be the total data throughput >>>>> speed reqired. 50 SPS is quite fast. The ADC sample rate can also >>>>> impose limitations. This starts to become serious when you have, say >>>>> several three off three channel sensors on the same ADC. >>>>> >>>>> Regards, >>>>> >>>>> Chris Chapman >>>>> >>>>> > > > > > >>> >>> > > > > > -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: "Thomas Dick" dickthomas01@............. Date: Sat, 5 Jan 2008 10:39:25 -0600 Are you familiar with UltraVNC Viewer. It allows me to access the earthquake recording computer anywhere I can find wifi? Some business computer articles give it a high security rating. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Sat, 05 Jan 2008 16:54:20 +0000 Hi, yes, I use it to look directly at my seismometer pc which is in the workshop. It works very well. Ian Thomas Dick wrote: > Are you familiar with UltraVNC Viewer. It allows me to access the > earthquake recording computer anywhere I can find wifi? Some business > computer articles give it a high security rating. > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ChrisAtUpw@....... Date: Sat, 5 Jan 2008 14:41:40 EST In a message dated 05/01/2008, ian@........... writes: Hi, actually, I don't think I'm near any limits. The A/D I use can handle 20K samples/sec. Hi Ian, What ADC are you using? 20 K SPS is 50 micro sec / sample. My ADC takes 20 muS/S. How does it's accuracy depend on it's sample rate? Does it have an onboard processor chip to take and average multiple samples? What data rate does the ADC board to computer link support? I only have 2 instruments (though I sample each on 3 A/D channels to get the resolution up to 22 bits), so that's only 6 x 50, or 300 samples/sec. You need to average four samples to get 1 additional bit of accuracy, 16 samples to get two bits extra, etc. So I could connect up all of the A/D's 16 input channels and still not stress it. This is likely to be ~40 bytes total with the overheads at 50 SPS, say 16 K bits/ sec. If you are using a 24 bit ADC, it is likely double this. Then it largely depends on whether you are sending datapackets, or individual bytes. If you are sending asynchronous bytes, you have to wait for the signal to be transmitted, the receiving server to respond and the ACK to be received. Transmission delays can be significant. I am 12 km from the phone terminal, so the delay would be well over 80 micro sec per byte. Coupled to a a 56 K modem, I certainly could not transmit this much data. The data server does burn up 80% of the PC's CPU but it's only an old 800 MHz machine and wouldn't cost much to replace with one twice the speed. Data across the network connection is only 32 characters x 50 or 1600 bytes/sec. Less than a 500th of the 100 Mb/s network bandwidth (being generous). So, do you know what minimum speed you can actually get for asynchronous transmissions? The broadband data rates quoted by the service providers are usually maximums in the best possible conditions, not the average and certinly not guaranteed. They may not allow for transmission delays. Reality may be only a small fraction of the specs advertised! A recent BB survey in the UK suggested a far lower preformance, nearer to that of the 56 K modems. Regards, Chris Chapman
In a message dated 05/01/2008, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Hi,
actually, I don't think I'm near any limits.  The A/D= I use=20 can handle 20K samples/sec. 
Hi Ian,
 
    What ADC are you using? 20 K SPS is 50 micro se= c /=20 sample. My ADC takes 20 muS/S.
    How does it's accuracy depend on it's sample=20 rate?
    Does it have an onboard processor chip to take=20= and=20 average multiple samples?
    What data rate does the ADC board to computer l= ink=20 support?
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I only=20 have 2 instruments (though I sample each on 3 A/D channels to get the=20 resolution up to 22 bits), so that's only 6 x 50, or 300 samples/sec. = ;=20
    You need to average four samples to get 1=20 additional bit of accuracy, 16 samples to get two bits extra, etc.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>So I=20 could connect up all of the A/D's 16 input channels and still not stress=20 it.
    This is likely to be ~40 bytes total with the=20 overheads at 50 SPS, say 16 K bits/ sec. If you are using a 24 bit ADC, it i= s=20 likely double this. Then it largely depends on whether you are sending=20 datapackets, or individual bytes.
    If you are sending asynchronous bytes, you have= to=20 wait for the signal to be transmitted, the receiving server to respond and t= he=20 ACK to be received. Transmission delays can be significant. 
    I am 12 km from the phone terminal, so the dela= y=20 would be well over 80 micro sec per byte. Coupled to a a 56 K modem, I certa= inly=20 could not transmit this much data.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>The data=20 server does burn up 80% of the PC's CPU but it's only an old 800 MHz machi= ne=20 and wouldn't cost much to replace with one twice the speed.  Data acr= oss=20 the network connection is only 32 characters x 50 or 1600 bytes/sec. = =20 Less than a 500th of the 100 Mb/s network bandwidth
(being=20 generous).
    So, do you know what minimum speed you=20 can actually get for asynchronous transmissions? The broadband data rat= es=20 quoted by the service providers are usually maximums in the best possible=20 conditions, not the average and certinly not guaranteed. They may not a= llow=20 for transmission delays. Reality may be only a small fraction of the specs=20 advertised! A recent BB survey in the UK suggested a far lower preformance,=20 nearer to that of the 56 K modems.
 
    Regards,
 
    Chris Chapman
Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Sat, 05 Jan 2008 22:08:22 +0000 Hi, I was waiting nervously for your reply and an array of astute questions; here they are! :-) I'll try to answer as best as possible. My A/D is a National Instruments AT-MIO-16XE-50 which plugs directly into the motherboard, so no communication issues. The data sheet is at http://www.ni.com/pdf/products/us/2mhw254-255e.pdf and the manual is at http://www.ni.com/pdf/manuals/370507a.pdf From the manual, sampling rate is only a consideration when switching gain between channels (which I am, see later), otherwise full tilt is fine. The board does have a micro with which it can perform various tricks. Higher bit systems give both higher resolution and higher dynamic range. I think the main concern for seismometry, amongst cash limited amateurs, is the dynamic range to try to avoid saturation when a strong signal comes in. So, with my 16 bit A/D, I feed the signal into 3 separate channels and sample each of them at 3 different gains, +/-0.1V, +/-1.0V and +/-10V. The software then chooses the reading with the greatest gain which hasn't saturated. So that gives it an "effective" bit rating of 20V/3.05e-6V or just over 22 bits for dynamic range but still 16 bits for resolution. As said above, changing gain between channels does have settling issues. To eliminate this effect, I should increase the intra-channel sampling time. However, this would increase the skew between the 3 samples, which would introduce another source of noise. I should really measure/calculate these competing effects and find the optimum point. For this application, though, I am content. I used to use a 12 bit system, so my present system is much better even with these features. I'm squirting the data across my own intranet to the graphing computer, so am getting most of the available 100 Mb/s bandwidth with minimal latency. For those using the internet, there shouldn't be a problem provided the data are timestamped at source. It then doesn't matter how long the data takes to arrive or whether the times between samples varies, the data can be properly reassembled using the individual timestamps. Things though are more limited with 56K modems. I'd be interested to hear how there is a 12 Km "gap" in your system. Cheers Ian http://www.iasmith.com/ http://www.festivalpreviews.com/ ChrisAtUpw@....... wrote: > In a message dated 05/01/2008, ian@........... writes: > > Hi, > actually, I don't think I'm near any limits. The A/D I use can > handle 20K samples/sec. > > Hi Ian, > > What ADC are you using? 20 K SPS is 50 micro sec / sample. My ADC > takes 20 muS/S. > How does it's accuracy depend on it's sample rate? > Does it have an onboard processor chip to take and average > multiple samples? > What data rate does the ADC board to computer link support? > > I only have 2 instruments (though I sample each on 3 A/D channels > to get the resolution up to 22 bits), so that's only 6 x 50, or > 300 samples/sec. > > You need to average four samples to get 1 additional bit of > accuracy, 16 samples to get two bits extra, etc. > > So I could connect up all of the A/D's 16 input channels and still > not stress it. > > This is likely to be ~40 bytes total with the overheads at 50 SPS, > say 16 K bits/ sec. If you are using a 24 bit ADC, it is likely double > this. Then it largely depends on whether you are sending datapackets, > or individual bytes. > If you are sending asynchronous bytes, you have to wait for the > signal to be transmitted, the receiving server to respond and the ACK > to be received. Transmission delays can be significant. > I am 12 km from the phone terminal, so the delay would be well > over 80 micro sec per byte. Coupled to a a 56 K modem, I certainly > could not transmit this much data. > > The data server does burn up 80% of the PC's CPU but it's only an > old 800 MHz machine and wouldn't cost much to replace with one > twice the speed. Data across the network connection is only 32 > characters x 50 or 1600 bytes/sec. Less than a 500th of the 100 > Mb/s network bandwidth > (being generous). > > So, do you know what minimum speed you can actually get for > asynchronous transmissions? The broadband data rates quoted by the > service providers are usually maximums in the best possible > conditions, not the average and certinly not guaranteed. They may not > allow for transmission delays. Reality may be only a small fraction of > the specs advertised! A recent BB survey in the UK suggested a far > lower preformance, nearer to that of the 56 K modems. > > Regards, > > Chris Chapman -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Wrong clock From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Sun, 06 Jan 2008 01:04:33 +0000 Hi all I did noticet that station that has the id jcc1 has a wrong clock in place. But according to the event file list, this is the date that it is using. 12/05/08 11:01 UTC 12/05/08 03:01 Local Time This is a massive time error. I hope that the owner can fix this before the next big quake near west coast of Canada. Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Sun, 06 Jan 2008 01:15:31 +0000 Hi all I do belive that West coast of Canada is at risk of getting a new big earthquake, possible around mag 6.5, but there is at least 12% chance of mag 7.0 or bigger earthquake in the area close to the two mag 6.5 earthquakes that did happen yesterday. Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ChrisAtUpw@....... Date: Sat, 5 Jan 2008 21:20:06 EST In a message dated 05/01/2008, ian@........... writes: I'm squirting the data across my own intranet to the graphing computer, so am getting most of the available 100 Mb/s bandwidth with minimal latency. Hi Ian, Communication links usually have fixed baud rates. What are you using? For those using the internet, there shouldn't be a problem provided the data are timestamped at source. It then doesn't matter how long the data takes to arrive or whether the times between samples varies, the data can be properly reassembled using the individual rimestamps. ? If you are sending asynchronous data, you send a byte maybe ~11 cycles long overall, which has start and stop bits. You usually send the signal, the receiver processes it and sends an ACK signal back. Then you send the next byte. If you try simply sending at a fixed baud rate, you inevitably get dropouts. You have to complete the process with the time stamp data to be able to reassemble it. Your bus also has a fixed interrupt repeat rate, when the CPU checks what tasks are currently waiting. Only a few interrupts in a multitasking system redirect the CPU instantly. Things though are more limited with 56K modems. I'd be interested to hear how there is a 12 Km "gap" in your system. Dead simple. This is the distance between my modem and the digital receiver in the phone exchange. 56 K modems rarely work at this rate. I limit mine to 38 K, sometimes less. This avoids my computer having to request a lot of data repeats, which can waste a lot of time. I note that the ADC board uses the computer supply lines. These can be quite noisy. What noise do you generally see with the input line to earth? How many times has your system had to use a restricted amplification range channel? These are only common if you get local quakes. I have yet to receive an out of range quake signal with my 16 bit +/-1/2 lsb system. Regards, Chris Chapman
In a message dated 05/01/2008, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I'm=20 squirting the data across my own intranet to the graphing computer, so am=20 getting most of the available 100 Mb/s bandwidth with minimal=20 latency.
Hi Ian,
 
    Communication links usually have fixed baud rat= es.=20 What are you using?
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>For=20 those using the internet, there shouldn't be a problem provided the data a= re=20 timestamped at source.  It then doesn't matter how long the data take= s to=20 arrive or whether the times between samples varies, the data can be proper= ly=20 reassembled using the individual rimestamps.
    ? If you are sending asynchronous data, you sen= d a=20 byte maybe ~11 cycles long overall, which has start and stop bits. You usual= ly=20 send the signal, the receiver processes it and sends an ACK signal back. The= n=20 you send the next byte. If you try simply sending at a fixed baud=20 rate, you inevitably get dropouts. You have to complete the process wit= h=20 the time stamp data to be able to reassemble it. Your bus also has a fixed=20 interrupt repeat rate, when the CPU checks what tasks are currently=20 waiting. Only a few interrupts in a multitasking system redirect the CP= U=20 instantly.
 
    Things though are more limited with 56K=20 modems.  I'd be interested to hear how there is a 12 Km "gap" in your=20 system.
 
    Dead simple. This is the distance between my mo= dem=20 and the digital receiver in the phone exchange.
 
    56 K modems rarely work at this rate. I lim= it=20 mine to 38 K, sometimes less. This avoids my computer having to request a lo= t of=20 data repeats, which can waste a lot of time.
 
    I note that the ADC board uses the computer sup= ply=20 lines. These can be quite noisy. What noise do you generally see with the in= put=20 line to earth?
 
    How many times has your system had to use a=20 restricted amplification range channel? These are only common if you ge= t=20 local quakes. I have yet to receive an out of range quake signal with my 16=20= bit=20 +/-1/2 lsb system.
 
    Regards,
 
    Chris Chapman
Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Sun, 06 Jan 2008 13:03:04 +0000 Hi, I've just had a refresher look at the software. The A/D board has it's own crystal controlled timing to trigger the sampling and to control the time between channel samples. There is also a 4000 sample FIFO buffer to store the readings, so the timing of the samples is absolutely rock solid and unaffected by activities on the pc. Where I deserve a wrist smack is the timestamps. These are applied as each sample group (the 3 samples for each of the 2 instruments) are read from the FIFO buffer and therefore are affected by activities on the pc. I'll add this to my todo list to use the A/D's internal timing for timestamps. For communication it's just standard 100 mbit tcp/ip. Totally transparent to the user and given that the data is all timestamped (sort of!) not something to worry about. I'll need to measure the noise to answer the noise question. Looking back I can see that there are a few traces (not many) which flipped between channel gains +/-0.1V and +/-1.0V. So the feature is giving me more gain to look into the weaker signals without being clobbered with saturation on the stronger traces - both the high and low pass filters apply a 20db gain to compensate for the attenuation of the filters. I asked about your 12 Km gap as I was wondering if there was a way to plug it with equipment running at broadband rates. I'm in one of the BT(our telco) "black spots", condemned to never have broadband and I eventually had to put together our own community wireless broadband (http://www.gmccbroadband.org/ ). This partly involves filling "gaps" across the countryside. Our biggest gap is only 5 Km so the stuff we use might not help. We use Tranzeo 5Ghz point-to-point access points, these require line of sight between the two locations. They might cover 12 Km but I'm not sure. Equipment is about Ł450 and you'll need to pay someone to install it on the roof. The other method is to rent a "private circuit" or EPS line from BT - a private wire between two premises sharing the same exchange - over which you can connect a pair of sdsl modems. These may not work over the distance, again I'm not sure. Costs about Ł45/month. Maybe that's what you are already doing. Cheers Ian http://www.iasmith.com http://www.festivalpreviews.com ChrisAtUpw@....... wrote: > In a message dated 05/01/2008, ian@........... writes: > > I'm squirting the data across my own intranet to the graphing > computer, so am getting most of the available 100 Mb/s bandwidth > with minimal latency. > > Hi Ian, > > Communication links usually have fixed baud rates. What are you using? > > For those using the internet, there shouldn't be a problem > provided the data are timestamped at source. It then doesn't > matter how long the data takes to arrive or whether the times > between samples varies, the data can be properly reassembled using > the individual rimestamps. > > ? If you are sending asynchronous data, you send a byte maybe ~11 > cycles long overall, which has start and stop bits. You usually send > the signal, the receiver processes it and sends an ACK signal back. > Then you send the next byte. If you try simply sending at a fixed baud > rate, you inevitably get dropouts. You have to complete the process > with the time stamp data to be able to reassemble it. Your bus also > has a fixed interrupt repeat rate, when the CPU checks what tasks are > currently waiting. Only a few interrupts in a multitasking system > redirect the CPU instantly. > > Things though are more limited with 56K modems. I'd be interested > to hear how there is a 12 Km "gap" in your system. > > Dead simple. This is the distance between my modem and the digital > receiver in the phone exchange. > > 56 K modems rarely work at this rate. I limit mine to 38 K, > sometimes less. This avoids my computer having to request a lot of > data repeats, which can waste a lot of time. > > I note that the ADC board uses the computer supply lines. These > can be quite noisy. What noise do you generally see with the input > line to earth? > > How many times has your system had to use a restricted > amplification range channel? These are only common if you get local > quakes. I have yet to receive an out of range quake signal with my 16 > bit +/-1/2 lsb system. > > Regards, > > Chris Chapman __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: "Geoff" gmvoeth@........... Date: Sun, 6 Jan 2008 16:34:47 -0700 Isnt that area a subduction zone ? You get the biggest EQs at subduction Zones. You might get one like thay had off sumatra one day. ----- Original Message ----- From: "Jón Frímann" To: Sent: Saturday, January 05, 2008 6:15 PM Subject: Re: Large earthquake near cost of Canada Hi all I do belive that West coast of Canada is at risk of getting a new big earthquake, possible around mag 6.5, but there is at least 12% chance of mag 7.0 or bigger earthquake in the area close to the two mag 6.5 earthquakes that did happen yesterday. Regards. -- Jón Frímann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: Bob Hancock carpediem1@......... Date: Sun, 06 Jan 2008 16:54:21 -0700 Geoff - The Queen Charlotte fault is a transform fault; however, there are sections both north and south that have different names and are either transform or subduction. The mechanics of these two major recent events indicate a strike slip movement. Bob Hancock On 1/6/08 4:34 PM, "Geoff" wrote: > Isnt that area a subduction zone ? > You get the biggest EQs at subduction Zones. >=20 > You might get one like thay had off sumatra one day. >=20 > ----- Original Message ----- > From: "J=F3n Fr=EDmann" > To: > Sent: Saturday, January 05, 2008 6:15 PM > Subject: Re: Large earthquake near cost of Canada >=20 >=20 > Hi all >=20 > I do belive that West coast of Canada is at risk of getting a new big > earthquake, possible around mag 6.5, but there is at least 12% chance of > mag 7.0 or bigger earthquake in the area close to the two mag 6.5 > earthquakes that did happen yesterday. >=20 > Regards. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ChrisAtUpw@....... Date: Sun, 6 Jan 2008 19:15:48 EST In a message dated 06/01/2008, ian@........... writes: Looking back I can see that there are a few traces (not many) which=20 flipped between channel gains +/-0.1V and +/-1.0V. So the feature is=20 giving me more gain to look into the weaker signals without being=20 clobbered with saturation on the stronger traces - both the high and low=20 pass filters apply a 20db gain to compensate for the attenuation of the =20 filters. Hi Ian, =20 I would expect that all your out of range signals will be due to the=20 surface waves?=20 I asked about your 12 Km gap as I was wondering if there was a way to=20 plug it with equipment running at broadband rates. I'm in one of the=20 BT(our telco) "black spots", condemned to never have broadband and I =20 eventually had to put together our own community wireless broadband =20 (http://www.gmccbroadband.org/ ). This partly involves filling "gaps"=20 across the countryside. Our biggest gap is only 5 Km so the stuff we=20 use might not help.=20 The delay that I quoted was due to the speed of light over the distance= ,=20 but the phase velocity in the wires will be lower. I have not measured it.=20 I only require four or five channels, not eight. =20 One standard fix is to send the data as packets, so greatly reducing th= e=20 number of delays..=20 We use Tranzeo 5Ghz point-to-point access points, these require line of=20 sight between the two locations. They might cover 12 Km but I'm not sure.=20= =20 Equipment is about =A3450 and you'll need to pay someone to install it on th= e roof. This is quite expensive. Even if I did install an aerial on my roof,=20 there is still a hill in the way. Nor does it solve the problem of the two= way=20 signal delays. =20 // At the RF level, the system also reduces latency and improves=20 throughput by allowing the user to adjust the RF ACK time, changing the amo= unt of=20 time the system will wait for an RF ACK to be returned. Radio waves take a=20 finite amount of time to reach a destination, namely the speed of light. Ev= ery=20 packet sent via an RF link needs to be acknowledged, in order to ensure that the packet was=20 received intact. // The other method is to rent a "private circuit" or EPS line from BT - a=20 private wire between two premises sharing the same exchange - over which y= ou can=20 connect a pair of sdsl modems. These may not work over the distance, agai= n=20 I'm not sure. Costs about =A345/month. Maybe that's=20 what you are already doing. I have not tried to explore this recently. When I last enquired, BT were no= t=20 prepared to lay an additional 12 km of phone line. And they didn't have a=20 spare line on their local cable. There is a relationship between the distan= ce=20 to the phone exchange and the maximum speed. There was also a maximum=20 distance. From memory this was about 5 km when I enquired. =20 Regards, =20 Chris Chapman =20
In a message dated 06/01/2008, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Looking=20 back I can see that there are a few traces (not many) which
flipped=20 between channel gains +/-0.1V and +/-1.0V.  So the feature is
giv= ing=20 me more gain to look into the weaker signals without being
clobbered w= ith=20 saturation on the stronger traces - both the high and low
pass filters= =20 apply a 20db gain to compensate for the attenuation of the=20
filters.
Hi Ian,
 
    I would expect that all your out of range signa= ls=20 will be due to the surface waves? 
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I asked=20 about your 12 Km gap as I was wondering if there was a way to
plug it=20= with=20 equipment running at broadband rates.  I'm in one of the
BT(our=20 telco)  "black spots", condemned to never have broadband and I=20
eventually had to put together our own community wireless broadband=20
(http://www.gmccbroadband.org/ ).  This partly involves filling=20 "gaps"
across the countryside.  Our biggest gap is only 5 Km so t= he=20 stuff we
use might not help.
    The delay that I quoted was due to the spe= ed=20 of light over the distance, but the phase velocity in the wires will be lowe= r. I=20 have not measured it.
    I only require four or five channels, not=20 eight.
 
    One standard fix is to send the data=20 as packets, so greatly reducing the number of delays..
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>We use=20 Tranzeo 5Ghz point-to-point access points, these require line of sight bet= ween=20 the two locations.  They might cover 12 Km but I'm not sure. =20 Equipment is about =A3450 and you'll need to pay someone to install it on=20= the=20 roof.
    This is quite expensive. Even if I did install=20= an=20 aerial on my roof, there is still a hill in the way. Nor does it  solve= the=20 problem of the two way signal delays.
 
//    At the RF level, the system also reduces late= ncy=20 and improves throughput by allowing the user to adjust the RF ACK time, chan= ging=20 the amount of time the system will wait for an RF ACK to be returned. Radio=20 waves take a finite amount of time to reach a destination, namely the speed=20= of=20 light. Every packet sent via an
RF link needs to be acknowledged, in orde= r to=20 ensure that the packet was received intact.
//
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>The=20 other method is to rent a "private circuit" or EPS line from BT - a privat= e=20 wire between two premises sharing the same exchange -  over which you= can=20 connect a pair of sdsl modems.  These may not work over the distance,= =20 again I'm not sure.  Costs about =A345/month.  Maybe that's
= what=20 you are already doing.
    I have not tried to explore this recently. When= I=20 last enquired, BT were not prepared to lay an additional 12 km of phone line= ..=20 And they didn't have a spare line on their local cable. There is a relations= hip=20 between the distance to the phone exchange and the maximum speed. There= was=20 also a maximum distance. From memory this was about 5 km when I=20 enquired.
 
    Regards,
 
    Chris Chapman
Subject: Re: Large earthquake near cost of Canada From: John Lahr johnjan@........ Date: Sun, 06 Jan 2008 16:58:21 -0800 The two M6.5 earthquakes of 1/5/2008 on the Queen=20 Charlotte Islands Fault were well recorded by=20 AS-1 stations all across the US. I've posted=20 some information from Robert Butler, along with two seismograms. http://jclahr.com/science/psn/as1/queen08/index.html They were both predominately strike-slip events. Cheers, John At 03:54 PM 1/6/2008, you wrote: >Geoff - > >The Queen Charlotte fault is a transform fault; however, there are sections >both north and south that have different names and are either transform or >subduction. The mechanics of these two major recent events indicate a >strike slip movement. > >Bob Hancock > > >On 1/6/08 4:34 PM, "Geoff" wrote: > > > Isnt that area a subduction zone ? > > You get the biggest EQs at subduction Zones. > > > > You might get one like thay had off sumatra one day. > > > > ----- Original Message ----- > > From: "J=F3n Fr=EDmann" > > To: > > Sent: Saturday, January 05, 2008 6:15 PM > > Subject: Re: Large earthquake near cost of Canada > > > > > > Hi all > > > > I do belive that West coast of Canada is at risk of getting a new big > > earthquake, possible around mag 6.5, but there is at least 12% chance of > > mag 7.0 or bigger earthquake in the area close to the two mag 6.5 > > earthquakes that did happen yesterday. > > > > Regards. > > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: "Thomas Dick" dickthomas01@............. Date: Sun, 6 Jan 2008 19:17:43 -0600 Wouldn't P be expected to be larger for this magnitude of a quake and the nearness to the epicenter? ----- Original Message ----- From: "John Lahr" To: Sent: Sunday, January 06, 2008 6:58 PM Subject: Re: Large earthquake near cost of Canada The two M6.5 earthquakes of 1/5/2008 on the Queen Charlotte Islands Fault were well recorded by AS-1 stations all across the US. I've posted some information from Robert Butler, along with two seismograms. http://jclahr.com/science/psn/as1/queen08/index.html __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: John Lahr johnjan@........ Date: Sun, 06 Jan 2008 18:20:01 -0800 Not really. At my station the P-wave amplitude was about 1.5 micrometers zero to peak. Based on this, I computed an mb of 7.0, using AmaSeis' built-in magnitude calculations: I added an image showing the calculation window to this page: http://jclahr.com/science/psn/as1/queen08/index.html (You may have to refresh your browser to see the new image at the bottom.) Given all of the factors that can influence the magnitude calculation, such as the approximate station calibration that we use for the AS-1 and the event radiation pattern (the USGS mb is computed from an average of for stations at many azimuths and distances), coming within 0.5 units is not too bad. The computed USGS mb was 6.2, so my amplitude was, if anything, a bit too large. The USGS preferred magnitude of 6.5 is an Mw. John At 05:17 PM 1/6/2008, Thomas Dick wrote: >Wouldn't P be expected to be larger for this magnitude of a quake >and the nearness to the epicenter? __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: "Thomas Dick" dickthomas01@............. Date: Sun, 6 Jan 2008 21:45:31 -0600 > Not really. At my station the P-wave amplitude was about 1.5 micrometers > zero to peak. Based on this, I computed an mb of 7.0, using AmaSeis' > built-in magnitude calculations: > > I added an image showing the calculation window to this page: > http://jclahr.com/science/psn/as1/queen08/index.html > (You may have to refresh your browser to see the new image at the bottom.) > Thanks for taking the time for me. I didn't know. Because of the shallowness of the focus and the closeness of your recording site, I "expected" P and S to have a more similar amplitude.....I am not taking about my recordings....it did surprise me that the Lehmans at my location seemed to be noisey in the P to PcS arrival time frame. And since I am taking up your time, another question, does the AS-1 show any directional sensitivity....maybe as the result of improper setup? __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: John Lahr johnjan@........ Date: Sun, 06 Jan 2008 21:10:49 -0800 This image: http://jclahr.com/science/psn/as1/as1_dim.jpg shows the construction of the AS-1. As long as the center of mass of the boom is at the same vertical elevation as the boom knife edge there will be no horizontal cross-axis sensitivity. The boom is prevented from rocking back and forth by the width of the knife edge. Also, rocking motion would not generate nearly as large a voltage, as it would not have the optimum orientation of 90 degrees for the cross product of the velocity vector with magnetic field vector. A knife edge is NOT the best type of hinge. You can find a lot of discussion of better hinge designs in the PSN E-mail archives. John At 07:45 PM 1/6/2008, Thomas Dick wrote: ..... does the AS-1 show any directional sensitivity....maybe as the result of improper setup? __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: ChrisAtUpw@....... Date: Mon, 7 Jan 2008 17:30:44 EST In a message dated 07/01/2008, johnjan@........ writes: This image: _http://jclahr.com/science/psn/as1/as1_dim.jpg_ (http://jclahr.com/science/psn/as1/as1_dim.jpg) shows the construction of the AS-1. As long as the center of mass of the boom is at the same vertical elevation as the boom knife edge there will be no horizontal cross-axis sensitivity. Hi Dick, One setup instruction seems to be missing from the current AS1 manual. When you have added load washers to the vertical bolt to level the arm for your particular spring / mass combination, you should then dismount the arm and hang it ~vertically (without the spring) by a strip of adhesive tape from the knife edge / hinge line. You then compare this to a vertical thread on a nut / a plumb line. You adjust the arm to hang vertically by moving the position of the mass balance washers held between the two clamp nuts. This offsets the mass of the red Alnico U magnet on the lower side of the arm. If you don't do this, the C of G will not be level with the hinge and you can get an appreciable sensitivity to horizontal Love waves. As far as I am aware, there is NO comparable method for setting up an EQ1 properly. Regards, Chris Chapman
In a message dated 07/01/2008, johnjan@........ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>This=20 image:  http://jclahr.com/s= cience/psn/as1/as1_dim.jpg=20 shows the construction of the AS-1.  As long as the center of mass of= the=20 boom is at the same vertical elevation as the boom knife edge
there wi= ll=20 be no horizontal cross-axis sensitivity.
Hi Dick,
 
    One setup instruction seems to be missing=20= from=20 the current AS1 manual.
    
    When you have added load washers to the vertica= l=20 bolt to level the arm for your particular spring / mass combination, you sho= uld=20 then dismount the arm and hang it ~vertically (without the spring) by a= =20 strip of adhesive tape from the knife edge / hinge line. You then compare th= is=20 to a vertical thread on a nut / a plumb line. You adjust the arm to han= g=20 vertically by moving the position of the mass balance=20 washers held between the two clamp nuts. This offsets the mass of=20= the=20 red Alnico U magnet on the lower side of the arm. 
 
    If you don't do this, the C of G will not be le= vel=20 with the hinge and you can get an appreciable sensitivity to horizontal Love= =20 waves.
 
    As far as I am aware, there is NO comparable me= thod=20 for setting up an EQ1 properly.
 
    Regards,
 
    Chris Chapman
Subject: Re: Hekla volcano geophone planned From: ChrisAtUpw@....... Date: Mon, 7 Jan 2008 19:15:07 EST In a message dated 06/01/2008, ian@........... writes: I asked about your 12 Km gap as I was wondering if there was a way to plug it with equipment running at broadband rates. I'm in one of the BT "black spots", condemned to never have broadband and I eventually had to put together our own community wireless broadband (http://www.gmccbroadband.org/ ). This partly involves filling "gaps" across the countryside. Our biggest gap is only 5 Km so the stuff we use might not help. Hi Ian, I rang BT today about Broadband. They offer 5 Meg at about 1 mile, 2 Meg at 3 miles and only 256 K much over that. The maximum length of a phone line is 14 miles. However, the UK is supposed to be fully rewired by 2010. ADSL are offering 5x the normal dial up rate, with signal compression and packeting, but I would like to see it in operation in a rural situation first. My experience is that I can only get about 38 K reliably at 12 km. I suspect that the current coverage outside towns with a phone exchange is very patchy. Your blog on the above website doesn't seem to work. Regards, Chris Chapman
In a message dated 06/01/2008, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I asked=20 about your 12 Km gap as I was wondering if there was a way to plug it with= =20 equipment running at broadband rates.  I'm in one of the BT "black=20 spots", condemned to never have broadband and I eventually had to put toge= ther=20 our own community wireless broadband
(http://www.gmccbroadband.org/=20 ).  This partly involves filling "gaps" across the countryside. = Our=20 biggest gap is only 5 Km so the stuff we use might not help.=20
Hi Ian,
 
    I rang BT today about Broadband. They offer 5 M= eg=20 at about 1 mile, 2 Meg at 3 miles and only 256 K much over that. The maximum= =20 length of a phone line is 14 miles. However, the UK is supposed to be fully=20 rewired by 2010. ADSL are offering 5x the normal dial up rate, with signal=20 compression and packeting, but I would like to see it in operation in a rura= l=20 situation first.
 
    My experience is that I can only get about 38 K= =20 reliably at 12 km. I suspect that the current coverage outside towns with a=20 phone exchange is very patchy.
 
    Your blog on the above website doesn't seem to=20 work.
 
    Regards,
 
    Chris Chapman
Subject: Re: Hekla volcano geophone planned From: "Thomas Dick" dickthomas01@............. Date: Mon, 7 Jan 2008 18:51:38 -0600 Would something like the amateur communication system using computers here in the U.S. be fast enough for you? And is it available to you? This is quite a bit of automation associated with that setup now (within the software).. I rang BT today about Broadband. They offer 5 Meg at about 1 mile, 2 Meg at 3 miles and only 256 K much over that. The maximum length of a phone line is 14 miles. However, the UK is supposed to be fully rewired by 2010. ADSL are offering 5x the normal dial up rate, with signal compression and packeting, but I would like to see it in operation in a rural situation first. My experience is that I can only get about 38 K reliably at 12 km. I suspect that the current coverage outside towns with a phone exchange is very patchy. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: "Thomas Dick" dickthomas01@............. Date: Mon, 7 Jan 2008 19:28:31 -0600 One setup instruction seems to be missing from the current AS1 manual. When you have added load washers to the vertical bolt to level the arm for your particular spring / mass combination, you should then dismount the arm and hang it ~vertically (without the spring) by a strip of adhesive tape from the knife edge / hinge line. You then compare this to a vertical thread on a nut / a plumb line. You adjust the arm to hang vertically by moving the position of the mass balance washers held between the two clamp nuts. This offsets the mass of the red Alnico U magnet on the lower side of the arm. If you don't do this, the C of G will not be level with the hinge and you can get an appreciable sensitivity to horizontal Love waves. As far as I am aware, there is NO comparable method for setting up an EQ1 properly. Hi Chris, hope you are doing OK with the New Year. The above seems hard... at least, to understand why. I didn't have to add any washers.I have been disappointed with my AS-1. It was the first instrument I had commerically built. The Lehmans are doing fine; sometimes a little noisier than I'd like. The performance of the AS-1 seems to vary---- I got better results from my 4.5 Hz geophone than on the AS-1 from yesterday's 1.4 mg on the New Madrid fault and yet the AS-1 did OK on the Greek quake. During the 2nd Queen Charlotte quake, the AS-1 showed little P while more LQ & LR than I expected. That is what precipitated my queries to John. I expected P to be higher in amplitude in Oregon -- even on the 1.4 mg on the New Madrid, the P was larger than the S . His comment about using something other than a razor blade edge didn't fall on deft ears...been wondering about that. Got a new billfold for Xmas...now have to find some money to put into it...JoAnn has reduced my allowance! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Large earthquake near cost of Canada From: John Lahr johnjan@........ Date: Mon, 07 Jan 2008 18:54:41 -0800 Hi Thomas, How does your AS-1 record compare with those posted here: http://www.iris.edu/amaseis/schools/ What is the closest station to you that has a record showing? When the AS-1 isn't working well the problem is often due to slight contact between the magnet and the coil, or between the damping washer and the oil container. Be sure to check these areas. The system will appear to work, as it will respond to your presence around the sensor, but it's will not record earthquakes well if there is any friction at these points. John At 05:28 PM 1/7/2008, you wrote: > One setup instruction seems to be missing from the current AS1 manual. > > When you have added load washers to the vertical bolt to level > the arm for your particular spring / mass combination, you should > then dismount the arm and hang it ~vertically (without the spring) > by a strip of adhesive tape from the knife edge / hinge line. You > then compare this to a vertical thread on a nut / a plumb line. You > adjust the arm to hang vertically by moving the position of the > mass balance washers held between the two clamp nuts. This offsets > the mass of the red Alnico U magnet on the lower side of the arm. > > If you don't do this, the C of G will not be level with the > hinge and you can get an appreciable sensitivity to horizontal Love waves. > > As far as I am aware, there is NO comparable method for setting > up an EQ1 properly. > > Hi Chris, hope you are doing OK with the New Year. The above seems > hard... at least, to understand why. I didn't have to add any > washers.I have been disappointed with my AS-1. It was the first > instrument I had commerically built. The Lehmans are doing fine; > sometimes a little noisier than I'd like. The performance of the > AS-1 seems to vary---- I got better results from my 4.5 Hz geophone > than on the AS-1 from yesterday's 1.4 mg on the New Madrid fault > and yet the AS-1 did OK on the Greek quake. During the 2nd Queen > Charlotte quake, the AS-1 showed little P while more LQ & LR than I > expected. That is what precipitated my queries to John. I expected > P to be higher in amplitude in Oregon -- even on the 1.4 mg on the > New Madrid, the P was larger than the S . His comment about using > something other than a razor blade edge didn't fall on deft > ears...been wondering about that. Got a new billfold for Xmas...now > have to find some money to put into it...JoAnn has reduced my > allowance! __________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with the body >of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ChrisAtUpw@....... Date: Mon, 7 Jan 2008 22:47:10 EST In a message dated 08/01/2008, dickthomas01@............. writes: Would something like the amateur communication system using computers here in the U.S. be fast enough for you? And is it available to you? This is quite a bit of automation associated with that setup now (within the software).. Hi Tom, Thanks for the thought. The basic problem is that my phone is about 12 km from the BT phone station. Even at the speed of light, the signal delay would be about 40 micro seconds each way, so a transmit + ACK would be >80 micro seconds assuming that the rest of the system were infinitely fast. This delay severely limits the communication speeds when you are sending single bytes. That way around it is to use a system which sends a large information packet. However, I can just about cope at the moment. Regards, Chris Chapman
In a message dated 08/01/2008, dickthomas01@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Would=20 something like the amateur communication system using computers here in th= e=20 U.S. be fast enough for you? And is it available to you? This is quite a b= it=20 of automation associated with that setup now (within the=20 software)..
Hi Tom,
 
    Thanks for the thought. The basic problem is th= at=20 my phone is about 12 km from the BT phone station. Even at the speed of ligh= t,=20 the signal delay would be about 40 micro seconds each way, so a transmit + A= CK=20 would be >80 micro seconds assuming that the rest of the system were= =20 infinitely fast. This delay severely limits the communication speeds when yo= u=20 are sending single bytes.
    That way around it is to use a system which sen= ds a=20 large information packet. However, I can just about cope at the moment.= =20
 
    Regards,
 
    Chris Chapman
Subject: Re: Hekla volcano geophone planned From: "Thomas Dick" dickthomas01@............. Date: Mon, 7 Jan 2008 22:46:49 -0600 Thanks for the thought. The basic problem is that my phone is about 12 km from the BT phone station. Even at the speed of light, the signal delay would be about 40 micro seconds each way, so a transmit + ACK would be >80 micro seconds assuming that the rest of the system were infinitely fast. This delay severely limits the communication speeds when you are sending single bytes. That way around it is to use a system which sends a large information packet. However, I can just about cope at the moment. Hey, when we get to heaven we will have all the speed and bandwideth we want ...... I wonder if there will be any earthquakes?? __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Thu, 10 Jan 2008 19:38:04 +0000 Hi, [earthquakish] I'm still not sure why you need deterministic communications. Isn't the data time stamped at source? If so, you don't need a deterministic link. I assume I've missed something. [non-earthquakish] I look forward to 2010 when I can give up my volunteer broadband service. I suspect, though, that those without service in the countryside now, won't get the new system either... The blog is only available to our subscribers as it is located on our intranet. We should make this clear on the web page. Yesterday's entry was about the 7 hour power cut caused by the storm that screamed across Scotland... Cheers Ian ChrisAtUpw@....... wrote: > In a message dated 06/01/2008, ian@........... writes: > > I asked about your 12 Km gap as I was wondering if there was a way > to plug it with equipment running at broadband rates. I'm in one > of the BT "black spots", condemned to never have broadband and I > eventually had to put together our own community wireless broadband > (http://www.gmccbroadband.org/ ). This partly involves filling > "gaps" across the countryside. Our biggest gap is only 5 Km so > the stuff we use might not help. > > Hi Ian, > > I rang BT today about Broadband. They offer 5 Meg at about 1 mile, > 2 Meg at 3 miles and only 256 K much over that. The maximum length of > a phone line is 14 miles. However, the UK is supposed to be fully > rewired by 2010. ADSL are offering 5x the normal dial up rate, with > signal compression and packeting, but I would like to see it in > operation in a rural situation first. > > My experience is that I can only get about 38 K reliably at 12 km. > I suspect that the current coverage outside towns with a phone > exchange is very patchy. > > Your blog on the above website doesn't seem to work. > > Regards, > > Chris Chapman __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ChrisAtUpw@....... Date: Thu, 10 Jan 2008 15:32:52 EST In a message dated 10/01/2008, ian@........... writes: [earthquakish] I'm still not sure why you need deterministic communications. Isn't the data time stamped at source? If so, you don't need a deterministic link. I assume I've missed something. Hi Ian, How are you defining 'deterministic communications' in this particular instance, please? The data is sent as individual bytes in a handshake process. If you don't receive all the bytes in a sequence correctly / all of them, how are you going to reconstitute / display / use that record? Regards, Chris Chapman
In a message dated 10/01/2008, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>[earthquakish]
I'm still not sure why you need deterministic=20 communications.  Isn't the
data time stamped at source?  If=20= so,=20 you don't need a deterministic
link.  I assume I've missed=20 something.
Hi Ian,
 
    How are you defining 'deterministic communicati= ons'=20 in this particular instance, please?
 
    The data is sent as individual bytes in a=20 handshake process. If you don't receive all the bytes in a sequence correctl= y /=20 all of them, how are you going to reconstitute /  display / use that=20 record? 
 
    Regards,
 
    Chris Chapman
 
Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Fri, 11 Jan 2008 12:02:01 +0000 I note that the ADC board uses the computer supply lines. These can be quite noisy. What noise do you generally see with the input line to earth? > > Chris Chapman I just did a very crude noise test: I unplugged the output of the filter (which is the input to the A/D in the PC) and shorted it. So, with a 1 metre cable attached I got mostly +/- 1 LSB and sometimes +/- 2 LSBs. I think that's pretty good, considering. Cheers Ian __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Hekla volcano geophone planned From: ChrisAtUpw@....... Date: Fri, 11 Jan 2008 09:34:58 EST In a message dated 11/01/2008, ian@........... writes: I note that the ADC board uses the computer supply lines. These can be quite noisy. What noise do you generally see with the input line to earth? I just did a very crude noise test: I unplugged the output of the filter (which is the input to the A/D in the PC) and shorted it. So, with a 1 metre cable attached I got mostly +/- 1 LSB and sometimes +/- 2 LSBs. I think that's pretty good, considering. Hi Ian, This sounds about average to me. It would be a lot better if you could take 16 samples and average them to give maybe +/-1/2 lsb. Cutting your dynamic range by x4 is better avoided. Regards, Chris Chapman
In a message dated 11/01/2008, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2> =20   I note that the ADC board uses the computer supply lines. These can= be=20 quite noisy. What noise do you generally see with the input line to=20 earth?

I just did a very crude noise test: I unplugged the output o= f=20 the filter (which is the input to the A/D in the PC) and shorted it. = So,=20 with a 1 metre cable attached I got mostly +/- 1 LSB and sometimes +/- 2=20 LSBs.  I think that's pretty good,=20 considering.
Hi Ian,
 
    This sounds about average to me. It would be a=20= lot=20 better if you could take 16 samples and average them to give maybe +/-1/2 ls= b.=20 Cutting your dynamic range by x4 is better avoided.
 
    Regards,
 
    Chris Chapman
Subject: Icelandic earthquake numbers for 2007 From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Sat, 12 Jan 2008 23:10:03 +0000 Hi all I am in school from Monday to Friday, so delays might happen on me sending in new earthquakes. IMO has released new earthquake numbers for the year 2007. But in 2007 IMO did record 15102 earthquakes. For earthquake numbers from 1991 to 2007 from IMO, check this web page. http://hraun.vedur.is/ja/viku/2007/vika_52/arlegur_qu.html Does anyone have an program that counts psn files and makes a text file output? I would really like to have such program, so I can get an idea how many earthquakes I am recording pr year. Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Nice local 2.1 From: Pete Rowe ptrowe@......... Date: Sun, 13 Jan 2008 10:32:34 -0800 (PST) My storm related noise has finally subsided. There is crisp 2.1 at 12:27 UTC this morning on my website. Pete ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Metal Suppliers From: ChrisAtUpw@....... Date: Sun, 13 Jan 2008 17:07:59 EST Hi Gerry, You might find some cost savings on a range of metals at _http://www.onlinemetals.com_ (http://www.onlinemetals.com) Regards, Chris Chapman
Hi Gerry,
 
    You might find some cost savings on a rang= e of=20 metals at http://www.onlinemetals.com
 
    Regards,
 
    Chris Chapman
 Subject: Re: Metal Suppliers From: "Jerry Payton" gpayton880@....... Date: Sun, 13 Jan 2008 16:16:28 -0600 Thanks Chris, but I didn't ask about metal suppliers. You must have run across an older email. Jerry ----- Original Message ----- From: ChrisAtUpw@....... To: gpayton880@....... ; psn-l@.............. Sent: Sunday, January 13, 2008 4:07 PM Subject: Re: Metal Suppliers Hi Gerry, You might find some cost savings on a range of metals at http://www.onlinemetals.com Regards, Chris Chapman
Thanks Chris, but I didn't = ask about=20 metal suppliers.  You must have run across an older = email.
Jerry
 
 
----- Original Message -----=20
From: ChrisAtUpw@.......=20
To: gpayton880@....... ; psn-l@..............
Sent: Sunday, January 13, 2008 4:07 PM
Subject: Re: Metal Suppliers

Hi Gerry,
 
    You might find some cost savings on a = range of=20 metals at http://www.onlinemetals.com
 
    Regards,
 
    Chris Chapman
 Subject: Unable To Verify This Quake ? From: "Geoff" gmvoeth@........... Date: Mon, 14 Jan 2008 02:01:27 -0700 Regional Event to GVA Pn = 11:13:45.2 2008JAN13 UTC Pg = 11:14:06.0 2008JAN13 UTC Sb = 11:15:14.8 2008JAN13 UTC Sg = 11:15:26.0 2008JAN13 UTC Estimated Origin Time 11:12:13 2008JAN13 UTC Delta about 6.0 Deg or 414 Statute Miles from GVA Magnatude estimated at around 4.0 from past experience at receiving such signals in the past. Can anyone concurr with this data because I do not see it reported anywhere and am not going to report it if no one else but ME has seen it too. I believe my arrival times to be good. Anyone Know ?? Regards; geoff GVA __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Unable To Verify This Quake ? From: AHrubetz@....... Date: Mon, 14 Jan 2008 11:56:54 EST I recorded this event which was prominent on both my vertical and short period horizontal. There was only one deflection which I presumed was the P wave?? I am away from home so cannot give you the exact time of the event now, but remember the event well because I kept checking the USGS web site to see if it was posted. Al Hrubetz Dallas, Texas **************Start the year off right. Easy ways to stay in shape. http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489
I recorded this event which was prominent on both my vertical a= nd=20 short period horizontal.  There was only one deflection which I=20 presumed was the P wave??  I am away from home so cannot give you the e= xact=20 time of the event now, but remember the event well because I kept=20 checking the USGS web site to see if it was posted.
Al Hrubetz
Dallas, Texas



Start the year off right. Easy wa= ys to stay in shape in the new year.
Subject: Re: Unable To Verify This Quake ? From: "Geoff" gmvoeth@........... Date: Mon, 14 Jan 2008 10:13:57 -0700 Howdy Al; You are not giving me enough information. This quake if it was real was big enough to be seen throughout this region and possibly into texas but not sure. If no one but me got it then someone may be feeding me false vibrations through the ground like a neighbor or ??? Low Rider with a fancy vibration player attached to his hydraulics ??? I would not put it past the human specie to play such games. Just a thought. Regards; geoff GVA ----- Original Message ----- From: To: Sent: Monday, January 14, 2008 9:56 AM Subject: Re: Unable To Verify This Quake ? >I recorded this event which was prominent on both my vertical and short > period horizontal. There was only one deflection which I presumed was the P > wave?? I am away from home so cannot give you the exact time of the event now, > but remember the event well because I kept checking the USGS web site to see > if it was posted. > Al Hrubetz > Dallas, Texas > > > > **************Start the year off right. Easy ways to stay in shape. > http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489 > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Metal Suppliers From: "Jack Ivey" ivey@.......... Date: Mon, 14 Jan 2008 13:47:18 -0500 More unsolicited advice: Also look at www.discountsteel.com - they have e.g. 5052 Aluminum plate 1/4" x 12" x 12" $19.04 =20 Jack =20 ________________________________ From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Jerry Payton Sent: Sunday, January 13, 2008 5:16 PM To: psn-l@.............. Subject: Re: Metal Suppliers =20 Thanks Chris, but I didn't ask about metal suppliers. You must have run across an older email. Jerry =20 =20 ----- Original Message -----=20 From: ChrisAtUpw@.......... To: gpayton880@....... ; psn-l@................. Sent: Sunday, January 13, 2008 4:07 PM Subject: Re: Metal Suppliers =20 Hi Gerry, =20 You might find some cost savings on a range of metals at http://www.onlinemetals.com =20 Regards, =20 Chris Chapman

More unsolicited advice: Also look = at www.discountsteel.com – = they have e.g. 5052 Aluminum plate 1/4” x 12” x 12” = $19.04

 

Jack

 

From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Jerry Payton
Sent: Sunday, January 13, = 2008 5:16 PM
To: psn-l@..............
Subject: Re: Metal = Suppliers

 

Thanks Chris, but I didn't ask = about metal suppliers.  You must have run across an older = email.

Jerry

 

=

 

=

----- Original Message ----- =

Sent: Sunday, January 13, 2008 4:07 = PM

Subject: Re: Metal Suppliers

 

=

Hi = Gerry,

 

=

    You might find some cost savings on a range of metals at http://www.onlinemetals.com

 

=

    Regards,

 

=

    Chris = Chapman

Subject: Re: Nice local 2.1 From: "Thomas Dick" dickthomas01@............. Date: Mon, 14 Jan 2008 13:32:48 -0600 I forgot -- Pete are your inj Arkansas ----- Original Message ----- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Nice local 2.1 From: Pete Rowe ptrowe@......... Date: Mon, 14 Jan 2008 11:38:49 -0800 (PST) Hi Thomas I'm in the east foothills of San Jose, CA. The nice thing about living in this location is that I never run out of nice local earthquakes. We had another little one at 15:16Z this morning. regards, Pete --- Thomas Dick wrote: > I forgot -- Pete are your inj Arkansas > ----- Original Message ----- > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email > PSN-L-REQUEST@.............. with > the body of the message (first line only): > unsubscribe > See http://www.seismicnet.com/maillist.html for more > information. > ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Nice local 2.1 From: "Thomas Dick" dickthomas01@............. Date: Mon, 14 Jan 2008 14:00:10 -0600 OK...there was 2.1 in Conring AR as well about that time.... __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: what is the email adr From: "Thomas Dick" dickthomas01@............. Date: Tue, 15 Jan 2008 10:09:36 -0600 what is the address for putting new files on PSN network...lost computer = that did it automatically?
what is the address for putting new = files on PSN=20 network...lost computer that did it = automatically?
Subject: WinSDR From: tchannel1@............ Date: Thu, 17 Jan 2008 06:32:35 -0700 I would like some help getting started using WinSDR. I don't wish to = bother the group, but if someone would like to email back and forth, I = have a bunch of basic questions. =20 Thanks, Ted
I would like some help getting started = using=20 WinSDR.   I don't wish to bother the group, but if someone = would like=20 to email back and forth, I have a bunch of basic = questions.   =20
 
Thanks, Ted
Subject: Shadow Zone map From: "Randy" rpratt@............. Date: Fri, 18 Jan 2008 21:59:07 -0600 Hi All, I think it was Jerry that asked about determining a shadow zone acouple = weeks back. I have found the link I remembered seeing that could be of = value. Try http://gc.kls2.com/ in the middle of the page for ranges. = You can paste in 6000nm,8000nm@........... to see a zone between 6000 = and 8000nm from my approx location as an example. Randy
Hi All,
 
I think it was Jerry that asked about = determining a=20 shadow zone acouple weeks back.  I have found the link I remembered = seeing=20 that could be of value.  Try http://gc.kls2.com/  in the middle = of the=20 page for ranges.  You can paste in 6000nm,8000nm@........... to see = a zone=20 between 6000 and 8000nm from my approx location as an = example.
 
Randy

 Subject: Re: Shadow Zone map From: "Jerry Payton" gpayton880@....... Date: Fri, 18 Jan 2008 22:06:47 -0600 Yes, it was me. And, I substituted my coordinates for a display. Thank you, Randy. Regard, Jerry ----- Original Message ----- From: Randy To: psn-l@.............. Sent: Friday, January 18, 2008 9:59 PM Subject: Shadow Zone map Hi All, I think it was Jerry that asked about determining a shadow zone acouple weeks back. I have found the link I remembered seeing that could be of value. Try http://gc.kls2.com/ in the middle of the page for ranges. You can paste in 6000nm,8000nm@........... to see a zone between 6000 and 8000nm from my approx location as an example. Randy
Yes, it was me.  And, I substituted my coordinates for a=20 display.  Thank you, Randy.
Regard,
Jerry
 
 
----- Original Message -----=20
From: Randy
Sent: Friday, January 18, 2008 9:59 PM
Subject: Shadow Zone map

Hi All,
 
I think it was Jerry that asked about = determining a=20 shadow zone acouple weeks back.  I have found the link I remembered = seeing=20 that could be of value.  Try http://gc.kls2.com/  in the middle = of the=20 page for ranges.  You can paste in 6000nm,8000nm@........... to see = a zone=20 between 6000 and 8000nm from my approx location as an = example.
 
Randy

 Subject: Shadow zone From: "Randy" rpratt@............. Date: Fri, 18 Jan 2008 22:52:24 -0600 I see you can also combine options. For instance I used a quake from = Yukon in first option along with shadow none in second option to get = both plotted. Example: mhe-67.93N 136.28W uses nearest airport in = place of coordinates to me about 3 miles and the quake coordinates. = Then second box is=20 6240nm,8520nm@.............. for the shadow zone. Randy
I see you can also combine = options.  For=20 instance I used a quake from Yukon in first option along with shadow = none in=20 second option to get both plotted.  Example:  mhe-67.93N = 136.28W =20 uses nearest airport in place of coordinates to me about 3 miles and the = quake=20 coordinates.  Then second box is
6240nm,8520nm@.............. = for the=20 shadow zone.
 
Randy

 Subject: Re: Shadow Zone map From: John Lahr johnjan@........ Date: Fri, 18 Jan 2008 21:50:21 -0800 Although it would make little difference to the display at the scale of the world map, the distances in nautical miles would more accurately be: 104 degrees * 111.2 km/degree = 11,565 km converts to 6244 nm 140 degrees * 111.2 km/degree = 15,568 km converts to 8406 nm I used this site for converting from km to nm: http://www.csgnetwork.com/nsmilekmconverter.html Cheers, John At 07:59 PM 1/18/2008, you wrote: >Hi All, > >I think it was Jerry that asked about determining a shadow zone >acouple weeks back. I have found the link I remembered seeing that >could be of value. Try http://gc.kls2.com/ in >the middle of the page for ranges. You can paste in >6000nm,8000nm@........... to see a zone between 6000 and 8000nm from >my approx location as an example. > >Randy __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Shadow Zone map From: "Jerry Payton" gpayton880@....... Date: Sat, 19 Jan 2008 07:40:21 -0600 "I used this site for converting from km to nm: http://www.csgnetwork.com/nsmilekmconverter.html" This one is quite good too: http://joshmadison.com/software/convert/ Jerry
"I used this site for converting from km to nm:  http://www.csgn= etwork.com/nsmilekmconverter.html"
This one is quite good too:  http://joshmadison.com/= software/convert/
 
Jerry
Subject: optical mouse sensor From: Randall Peters PETERS_RD@.......... Date: Sat, 19 Jan 2008 09:41:05 -0500 My colleague, John Lee, and I have developed a package that may be interesting to amateur seismologists. A paper has been posted at http://physics.mercer.edu/hpage/mouse-sensor.pdf As noted in this article, John will make available free to anybody who sends him an email request for a password--the LabView executable to operate the mouse. The resolution, at about 50 microns, is too small for direct application to seismology; however the method might be useful for calibrating instruments. Also, anybody wanting to monitor the earth (stable pendulum as a plumb-bob) should be able to use this technique to watch for changes greater than 50 microradians. The typical diurnal thermoelastic variation is about one-third that value, but over the course of weeks to months I predict there will be observable changes that are not being routinely measured in nearly the 'global' sense they ought to be. To allow easier use of the sensor I removed some materal from the bottom of my mouse using sandpaper. By this means the gap-space over which the unit can operate is approximately doubled. Without doing so, one has to be more careful with alignment and stability of the pendulum. With my present capability (as wide as 3 mm) it is very easy to work with this instrument. Additionally, I have an idea that some of you may want to consider. Any truly outstanding vertical seismograph requires force-feedback. The traditional approach is one that uses force balance. The same 'strong' force that keeps the instrument from even moving substantially (much less 'goiing to the rails' because of temperature/pressure changes) is also used to provide the required near-critical damping. For more than a year I have demonstrated with my modified Sprengnether, that a 'soft' force feedback has advantages over the traditional approach. The feedback I have used with my Sprengnether derives from a long time constant integrated output from the capacitive sensor (large dynamic range area-varying, fully-differential unit). Based on my experience with this instrument, I propose the following: Since the sensor used for force feedback can have terrible sensitivity compared to the sensor used for detecting earthquakes--build a `centering' (feedback) package that uses the mouse sensor. The requirement for DAC output for the coil of the actuator can be managed (it appears) with a 'dirt cheap' homebuilt piece of electronics (an example at http://www.allaboutcircuits.com/vol_4/chpt_13/3.html ) Without a parallel port, your USB computer would need a printer cable (< $20) to operate this R/2R DAC. Randall Subject: Re: optical mouse sensor From: Brett Nordgren Brett3mr@............. Date: Sat, 19 Jan 2008 11:06:46 -0500 Dr. Peters, Could you elaborate a bit on your comment that one sensor used for force feedback can have low sensitivity compared with another one used for detecting earthquakes? It's not clear to me why that is. Thanks for your help, Brett Nordgren At 09:41 AM 1/19/2008 -0500, you wrote: >My colleague, John Lee, and I have developed a package that may be >interesting to amateur seismologists. > Additionally, I have an idea that some of you may want to >consider. > Any truly outstanding vertical seismograph requires force-feedback. >The traditional approach is one that uses force balance. >Since the sensor used for force feedback can have terrible >sensitivity compared to the sensor used for detecting earthquakes--build >a `centering' (feedback) package that uses the mouse sensor. My e-mail address above should be working, but if not you can always use my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Shadow Zone map From: John Lahr johnjan@........ Date: Sat, 19 Jan 2008 08:48:41 -0800 At 05:40 AM 1/19/2008, you wrote: >"I used this site for converting from km to >nm: >http://www.csgnetwork.com/nsmilekmconverter.html" >This one is quite good >too: >http://joshmadison.com/software/convert/ > >Jerry It probably makes more sense to use the definition of nautical mile to convert directly from degrees to nautical miles. http://en.wikipedia.org/wiki/Nautical_mile: A nautical mile "corresponds approximately to one minute of latitude along any meridian. " Since there are 60 minutes per degree, 104*60 = 6240 nm 140*60 = 8400 nm Cheers, John __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: optical mouse sensor From: ChrisAtUpw@....... Date: Sat, 19 Jan 2008 23:10:59 EST In a message dated 19/01/2008, PETERS_RD@.......... writes: A paper has been posted at _http://physics.mercer.edu/hpage/mouse-sensor.pdf_ (http://physics.mercer.edu/hpage/mouse-sensor.pdf) Hi Randall, The AD698 LVDT chip is not suitable for use with seismometers. Apart from being hideously expensive, it is also quite noisy. You can't get the very high resolution required. Single channel 16 bit Sigma Delta ADC chips start from about $5, not $25. The Linear ones seem to work fine. Regards, Chris
In a message dated 19/01/2008, PETERS_RD@.......... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>A paper=20 has been posted at http://physics.m= ercer.edu/hpage/mouse-sensor.pdf
Hi Randall,
 
    The AD698 LVDT chip is not suitable for use wit= h=20 seismometers. Apart from being hideously expensive, it is also quite noisy.=20= You=20 can't get the very high resolution required.
 
    Single channel 16 bit Sigma Delta ADC chips sta= rt=20 from about $5, not $25. The Linear ones seem to work fine.
 
    Regards,
 
    Chris
Subject: RE: optical mouse sensor From: "Fikke, Audun" Audun.Fikke@......... Date: Sun, 20 Jan 2008 08:08:31 +0100 I wonder if the high end models for gaming and design purposes will make = a difference.=20 They utilize a lazer and some has a resolution of 9000dpi. Just wondering Audun=20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Randall Peters Sent: l=F8rdag 19 januar 2008 15:41=20 To: psn-l@.............. Subject: optical mouse sensor My colleague, John Lee, and I have developed a package that may be = interesting to amateur seismologists. A paper has been posted at = http://physics.mercer.edu/hpage/mouse-sensor.pdf As noted in this article, John will make available free to anybody = who sends him an email request for a password--the LabView executable to = operate the mouse. The resolution, at about 50 microns, is too small for direct = application to seismology; however the method might be useful for = calibrating instruments. Also, anybody wanting to monitor the earth = (stable pendulum as a plumb-bob) should be able to use this technique to = watch for changes greater than 50 microradians. The typical diurnal = thermoelastic variation is about one-third that value, but over the = course of weeks to months I predict there will be observable changes = that are not being routinely measured in nearly the 'global' sense they = ought to be. To allow easier use of the sensor I removed some materal from the = bottom of my mouse using sandpaper. By this means the gap-space over = which the unit can operate is approximately doubled. Without doing so, = one has to be more careful with alignment and stability of the pendulum. = With my present capability (as wide as 3 mm) it is very easy to work = with this instrument. Additionally, I have an idea that some of you may want to = consider. Any truly outstanding vertical seismograph requires force-feedback. The traditional approach is one that uses force balance. The same = 'strong' force that keeps the instrument from even moving substantially = (much less 'goiing to the rails' because of temperature/pressure changes) is also used to provide the required near-critical damping. For more than a year I have demonstrated with my modified Sprengnether, = that a 'soft' force feedback has advantages over the traditional = approach. The feedback I have used with my Sprengnether derives from a = long time constant integrated output from the capacitive sensor (large = dynamic range area-varying, fully-differential unit). Based on my = experience with this instrument, I propose the following: Since the sensor used for force feedback can have terrible = sensitivity compared to the sensor used for detecting earthquakes--build = a `centering' (feedback) package that uses the mouse sensor. The = requirement for DAC output for the coil of the actuator can be managed = (it appears) with a 'dirt cheap' homebuilt piece of electronics (an = example at http://www.allaboutcircuits.com/vol_4/chpt_13/3.html ) Without a parallel port, your USB computer would need a printer = cable (< $20) to operate this R/2R DAC. Randall __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: AD698 chip From: Randall Peters PETERS_RD@.......... Date: Sun, 20 Jan 2008 07:39:39 -0500 Chris, Have you actually built an instrument with the AD698 chip and determined that it is unsuitable for seismometers? I remember you telling me this some time ago; but it turns out that Denny Goodwin (mentioned in the paper that John and I just wrote) put together a circuit for me, also some time ago. Only in the last month did I try his breadboarded unit. He had been unsuccessful with it due to a solder bridge that I found only after looking at the board carefully with magnification. You will remember that for much of the two decades I have been using my fully differential capacitive sensors for internal friction research--that the work-horse for that work was the NE5521 chip that is no longer manufactured (following the fire at the plant in France). Well, I have done a direct comparison of the AD698 with the Ne5521 and do not find a great enough performance difference to agree with your claim! In fact, with the prototype new vertical that I recently built (the details of which I will soon share with list-serve readers), it picked up the Charlotte Is earthquake with this chip, even though the instrument was sitting on a lab bench here in the physics building. So I don't think you can make a defensible claim that the chip is unsuitable for seismometers. Insofar as expense is concerned, the webpage I recently viewed at Analog Devices indicates a price of about $25 (straight from the companry) for the version that I would use (in large quantities). I haven't enquired about single chip prices, although I know from Larry Cochrane that if bought from some of the 'distributors' it is indeed hideously expensive. They love to mark-up units, evidently in this case by a huge amount. The price I mention for ADC's in our paper ($25) is not for ADC chips that require peripheral components and labor to make operational, but rather the ones 'ready to go' from the distributor (like the 10-bit unit from Dataq). Randall Subject: mouse with 9000 dpi From: Randall Peters PETERS_RD@.......... Date: Sun, 20 Jan 2008 09:27:46 -0500 Audun, I believe the now fairly old Compaq optical mouse that was used for our paper has only 800 dpi. Thus, the 9000 dpi of a laser mouse should yield at least an order of magnitude improvement in the resolution. Since it would be relatively easy to operate with a pendulum at least 2 m long (enclosed, of course to prevent the influence of air drafts), such a mouse should permit one to observe angular displacement changes at the level of about 2 micro radians. I think this would be well worth pursuing, especially for purpose of studying long term changes in the 'figure' of the Earth. ( Even at 20 micro-radians the daily thermoelastic variation should be close to observable with the right kind of filtering. ) I have spent a good part of my career looking at motions with periods greater than 1000 s, a field deserving of much more study. For example, the VolksMeter data from both Redwood City and also here in Macon show an unmistakeable terdiurnal tide (8-h periodicity) that has never before been observed with a simple pendulum. I believe that an "army of amateurs" looking at diurnal variations of a simple pendulum monitored by a mouse just might uncover some unknown secrets of our planet. The terdiurnal tide is best known in relationship to the atmosphere. Randall Subject: seismometer misconceptions From: Randall Peters PETERS_RD@.......... Date: Sun, 20 Jan 2008 09:57:03 -0500 From a number of comments and questions that have appeared on the list serve over the last month or so, it appears that some of you might benefit (if I were to write it) from something booklet-like titled, "The Physics of a Seismometer" ?? The appropriate level of mathematics (language of physics) is something I haven't yet decided. There are important issues that could be addressed, independent of the math (unless proof is required for unbelievers), such as the following: Seismometer misconceptions There is a great deal of misunderstanding when it comes to the physics of seismometers. The biggest single contributor to confusion involves 'period' of the instrument. Only for a simple (ideal) pendulum (horizontal seismometer) or a simple (idealized) vertical spring holding a mass (vertical seismometer)--does the inherent (mechanical) sensitivity of the device depend quadratically on the natural period of oscillation; i.e., proportional to T squared. This is the natural period T of harmonic motion if the unit were not dampened to prevent oscillation, as is done with virtually all instruments other than some I find (evidently as a 'heretic'), quite useful. The sensitivity to the ground's acceleration (ONLY thiing that any seismometer responds to) is only 'half' the story. The instrument's sensitivity to its own structural changes is also proportional to T-squared. Because the instrument is under considerable stress by attempting to statically support at equilibrium the inertial mass required for it to function--the structural changes can not be ignored for any truly useful instrument. In particular, creep never ceases, and even miniscule varaiations in temperature can have a large effect. Trying to eliminate the structural influence as compared to the acceleration influence is the GREAT challenge of any instrument design. The tradeoff that is part of the design must weigh mechanical benefit versus electronics benefit. Keep in mind that linear electronics by iteself (WITHOUT force feedback) can never influence the instrument in a quadratic manner (as implied by the very word LINEAR). In other words reducing the corner freqeuency of the passive electronics (devoid of an actuator to provide feedback) can NEVER be as influential as lowering the natural frequency (lengthening the period) of the mechanical oscillator itself. Because electronics establishes a lower threshold of detectability (due to 1/f noise from the amplifiers and also white (frequency independent) noise due to ADC bit resolution) there is a vastly greater benefit from mechanical improvement than there is from electronics improvement. That shouldn't come as a great surprise. After all, you could have perfect electronics, but if the mass doesn't move under the influence of ground acceleration, then the seismometer will not respond. At low levels that is exactly what can prevent earthquake detection. It has nothing to do with the motion being below the threshold established by the noise of the electronics; it has everything to do with the system being 'latched' in a metastability that derives from internal friction that operates at the mesoscale. When seismologists talk about nonlinearity of the mechanical system (which is religiously avoided), what they are discussing is elastic anharmonicity (nonlinearity)--undesirable distortions at large levels of motion. Also very important but unknown until recently, are the influences of damping anharmonicity that derives from internal friction (changes in the defect structure of the spring) and which operates at the other extreme; i.e., at low levels. For information about damping anharmonicity, consult the article titled "anharmonic oscillator" that I wrote for the 10th Ed. of the McGraw Hill Encyclopedia of Science and Technology Practical seismometers are rarely configured with an appearance even remotely similar to the simple harmonic oscillators of idealized type mentioned above (pendulum or mass/spring). Their performance is governed by properties due to their "compound" nature. Many of the commercial instruments employ "force-balance", in which the inertial mass is constrained (by means of an actuator that is part of a force-feedback network) to execute very little motion in response to earth acceleration. Instead of monitoring the motion of the inertial mass relative to the case, what is monitored is the error signal of the electronics required to keep the mass from moving. In the case of force-balance this is indeed a large force, since it is used to not only keep the mean position of the mass from changing; but it is even great enough to prevent oscillation. In other words, the feedback is tailored to provide the desired near critical damping. With the forcing function of the actuator being large enough to provide this damping, it is also true that the feedback can be designed (in a manner analogous to PID controller design) to yield an instrument that behaves (by reason of the feedback) as though it were a simple oscillator with a much longer natural period. Keep in mind that the period lengthening results only from the feedback force supplied by the actuator. Electronics without feedback can never accomplish the same thing! Note also that it is the strong feedback force that results in a quadratic improvement in the idealized sensitivity--because the "effective mechanical natural period" has been increased. One might then think that force-feedback is the answer to every problem; but it is not! The additional complexity and cost are only part of the matter. There must be a small amount of inertial mass motion for the electronics to be able to generate an error signal. This is not always possible. The damping anharmonicity that I mentioned 'wars against' the force-balance concept. An alternative approach which has merit and which I alone appear to have used, is the following--instead of (i) a 'hard' feedback force (commercial standard) that is able to greatly alter the properties of the equivalent mechanical oscillator, use (ii) a 'soft' feedback force that keeps the system from migrating out the range of acceptable motion, but which allows the instrument to 'seek its own best equilibrium' while 'skating over the metastabilities of its real as opposed to idealized harmonic potential'. Randall Subject: Re: seismometer misconceptions From: "Daryl P. Dacko" mycrump@........ Date: Sun, 20 Jan 2008 11:37:24 -0500 Randall, I've been following your arguments about seismometer design for quite some time. I need a few answers to help my understanding. First, what's your definition of "mesoscale." Second, if you use "soft" damping, how do you separate the signal from the noise (overshoot and metainstabilitys that are allowed by the soft damping.) Third, when you talked before about using totally undamped systems, again, how do you separate signal from the undamped response ? Thanks for all the thought provoking ideas, Daryl > >From a number of comments and questions that have appeared on the list serve over the last month or so, > it appears that some of you might benefit (if I were to write it) from something booklet-like titled, > "The Physics of a Seismometer" ?? > The appropriate level of mathematics (language of physics) is something I haven't yet decided. > There are important issues that could be addressed, independent of the math (unless proof is required for > unbelievers), such as the following: > > Seismometer misconceptions > > There is a great deal of misunderstanding when it comes to the physics of seismometers. The biggest > single contributor to confusion involves 'period' of the instrument. Only for a simple (ideal) pendulum > (horizontal seismometer) or a simple (idealized) vertical spring holding a mass (vertical > seismometer)--does the inherent (mechanical) sensitivity of the device depend quadratically on the > natural period of oscillation; i.e., proportional to T squared. This is the natural period T of harmonic > motion if the unit were not dampened to prevent oscillation, as is done with virtually all instruments > other than some I find (evidently as a 'heretic'), quite useful. > The sensitivity to the ground's acceleration (ONLY thiing that any seismometer responds to) is only > 'half' the story. The instrument's sensitivity to its own structural changes is also proportional to > T-squared. Because the instrument is under considerable stress by attempting to statically support at > equilibrium the inertial mass required for it to function--the structural changes can not be ignored for > any truly useful instrument. In particular, creep never ceases, and even miniscule varaiations in > temperature can have a large effect. Trying to eliminate the structural influence as compared to the > acceleration influence is the GREAT challenge of any instrument design. > The tradeoff that is part of the design must weigh mechanical benefit versus electronics benefit. > Keep in mind that linear electronics by iteself (WITHOUT force feedback) can never influence the > instrument in a quadratic manner (as implied by the very word LINEAR). In other words reducing the > corner freqeuency of the passive electronics (devoid of an actuator to provide feedback) can NEVER be as > influential as lowering the natural frequency (lengthening the period) of the mechanical oscillator > itself. Because electronics establishes a lower threshold of detectability (due to 1/f noise from the > amplifiers and also white (frequency independent) noise due to ADC bit resolution) there is a vastly > greater benefit from mechanical improvement than there is from electronics improvement. That shouldn't > come as a great surprise. After all, you could have perfect electronics, but if the mass doesn't move > under the influence of ground acceleration, then the seismometer will not respond. At low levels that is > exactly what can prevent earthquake detection. It has nothing to do with the motion being below the > threshold established by the noise of the electronics; it has everything to do with the system being > 'latched' in a metastability that derives from internal friction that operates at the mesoscale. When > seismologists talk about nonlinearity of the mechanical system (which is religiously avoided), what they > are discussing is elastic anharmonicity (nonlinearity)--undesirable distortions at large levels of > motion. Also very important but unknown until recently, are the influences of damping anharmonicity that > derives from internal friction (changes in the defect structure of the spring) and which operates at the > other extreme; i.e., at low levels. For information about damping anharmonicity, consult the article > titled "anharmonic oscillator" that I wrote for the 10th Ed. of the McGraw Hill Encyclopedia of Science > and Technology > Practical seismometers are rarely configured with an appearance even remotely similar to the simple > harmonic oscillators of idealized type mentioned above (pendulum or mass/spring). Their performance is > governed by properties due to their "compound" nature. Many of the commercial instruments employ > "force-balance", in which the inertial mass is constrained (by means of an actuator that is part of a > force-feedback network) to execute very little motion in response to earth acceleration. Instead of > monitoring the motion of the inertial mass relative to the case, what is monitored is the error signal of > the electronics required to keep the mass from moving. In the case of force-balance this is indeed a > large force, since it is used to not only keep the mean position of the mass from changing; but it is > even great enough to prevent oscillation. In other words, the feedback is tailored to provide the > desired near critical damping. With the forcing function of the actuator being large enough to provide > this damping, it is also true that the feedback can be designed (in a manner analogous to PID controller > design) to yield an instrument that behaves (by reason of the feedback) as though it were a simple > oscillator with a much longer natural period. Keep in mind that the period lengthening results only from > the feedback force supplied by the actuator. Electronics without feedback can never accomplish the same > thing! Note also that it is the strong feedback force that results in a quadratic improvement in the > idealized sensitivity--because the "effective mechanical natural period" has been increased. > One might then think that force-feedback is the answer to every problem; but it is not! The > additional complexity and cost are only part of the matter. There must be a small amount of inertial > mass motion for the electronics to be able to generate an error signal. This is not always possible. > The damping anharmonicity that I mentioned 'wars against' the force-balance concept. An alternative > approach which has merit and which I alone appear to have used, is the following--instead of (i) a 'hard' > feedback force (commercial standard) that is able to greatly alter the properties of the equivalent > mechanical oscillator, use (ii) a 'soft' feedback force that keeps the system from migrating out the > range of acceptable motion, but which allows the instrument to 'seek its own best equilibrium' while > 'skating over the metastabilities of its real as opposed to idealized harmonic potential'. > > Randall > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Shadow Zone From: "Randy" rpratt@............. Date: Sun, 20 Jan 2008 16:10:34 -0600 The 1 NM per minute of latitude conversion is where I started as that is = what we used when I was flying. I see the shadow zone has a range of = definitions from 102 to 105 as beginning and 140 to 142 as ending = depending on the reference. Is there a most accepted range or is it = somewhat dependent on location? Is it a sharp cutoff or a gradual = reduction over a few degrees? Randy
The 1 NM per minute of latitude = conversion is where=20 I started as that is what we used when I was flying.  I see the = shadow zone=20 has a range of definitions from 102 to 105 as beginning and 140 to 142 = as ending=20 depending on the reference.  Is there a most accepted range or is = it=20 somewhat dependent on location?  Is it a sharp cutoff or a gradual=20 reduction over a few degrees?
 
Randy
Subject: Re: optical mouse sensor From: Charles R Patton charles.r.patton@........ Date: Sun, 20 Jan 2008 18:30:29 -0800 Dr. Peters, I’d like to comment on one point in your pendulum paper where you mention, “In general there is a tendency for the mean position of the displayed waveform to migrate in spite of the absence of actual physical migration.” You surmise a Windows problem. I don’t believe it’s in Windows. Windows can’t tell what mouse is on the end of the plug – just that it’s a mouse, not if it’s made of encoder disks or optical sensor. These sensors would require different algorithms to process raw data. A while back I started looking at the optical mouse as a optical encoder for use as a (ham) antenna position indicator. I abandoned the project when it became clear that the mouse itself does not put out a consistent, repeatable stream of pulses. I attribute this to the method of sensing that essentially does a center-of-light or center-of-darkness (the microscopic shadows cast from edge lighting of surface roughness) then estimates their change in position on the optical cell fields. The problem is that this is fuzzy involving coarse resolution a/d’s (that are very likely noisy, also) for each cell. So the simple test I did was just to run the mouse back and forth along a straight edge to stops. I would see the endpoints drift as this was repeated. I tried to develop a grating like pattern to turn the estimation into a fixed grating on the cells, figuring maybe I could get around the granularity, but didn’t finish the project. Nonetheless, sometimes the sensor will sit there and jitter or drift, even when it is standing still, which again I attribute to poor sensor algorithms in the mouse itself. Some optical mice use early versions of the HP sensor that can be re-jumpered to put out quadrature pulses instead of the mouse communication bytes. I didn’t do this experiment, but your pendulum would be perfect for it – just re-jumper one of those units for quadrature, and verify that the total is zero at the end of a swing down run. I’m sure you’ll find that it won’t be. Regards, Charles R. Patton __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: AD698 chip From: ChrisAtUpw@....... Date: Sun, 20 Jan 2008 22:45:19 EST In a message dated 20/01/2008, PETERS_RD@.......... writes: Chris, Have you actually built an instrument with the AD698 chip and determined that it is unsuitable for seismometers? I remember you telling me this some time ago; but it turns out that Denny Goodwin put together a circuit for me, also some time ago. Only in the last month did I try his breadboarded unit. He had been unsuccessful with it due to a solder bridge that I found only after looking at the board carefully with magnification. Hi Randall, If you read up the specifications, you will find that the output of the AD698 is PULSED ! The pulse length is modified to give the temperature compensation. I don't know what the ??designers?? at AD thought that they were doing. DigiKey list the AD698 DIP version at $70.88. The AD598 does not have this problem, but the DIP version still costs $52.53 for 1 off. The SOIC versions are about half this in small quantities, when stocked. You will remember that for much of the two decades I have been using my fully differential capacitive sensors for internal friction research--that the work-horse for that work was the NE5521 chip that is no longer manufactured. Well, I have done a direct comparison of the AD698 with the NE5521 and do not find a great enough performance difference to agree with your claim! In fact, with the prototype new vertical that I recently built (the details of which I will soon share with list-serve readers), it picked up the Charlotte Is earthquake with this chip, even though the instrument was sitting on a lab bench here in the physics building. So I don't think you can make a defensible claim that the chip is unsuitable for seismometers. The correction is temperature dependant, so there will likely be one temperature at which the correction is zero, presumably at one end of the range. If you digitise the output directly, you will get an uncompensated signal and occasional glitches due to the variable zero output periods. To get the compensated output you need to provide a low pass filter to integrate the signal. This may slow up the response if you want to get low noise. Trying to use a chip with a stepped level output in a low noise application seems to be 'simply buying trouble'. I am quite happy to avoid using it, particulaly when I can make up a good detector for a small fraction of the cost. _http://www.keckec.com/seismo/_ (http://www.keckec.com/seismo/) Insofar as expense is concerned, the webpage I recently viewed at Analog Devices indicates a price of about $25 (straight from the companry) for the version that I would use (in large quantities). I haven't enquired about single chip prices, although I know from Larry Cochrane that if bought from some of the 'distributors' it is indeed hideously expensive. They love to mark-up units, evidently in this case by a huge amount. You might cross check those prices again? The ''low'' AD website price I saw quoted was for the PLCC version in 1,000 off quantities. The 15 off price for the DIP version is $60. Regards, Chris
In a message dated 20/01/2008, PETERS_RD@.......... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Chris,
      Have you actually built an instrum= ent=20 with the AD698 chip and determined that it is unsuitable for=20 seismometers?
I remember you telling me this some time ago; but it turn= s=20 out that Denny Goodwin put together a circuit for me, also some time=20 ago.  Only in the last month did I try his breadboarded unit. &n= bsp;=20 He had been unsuccessful with it due to a solder bridge that I found only=20 after looking at the board carefully with magnification.
Hi Randall,
 
    If you read up the specifications, you will fin= d=20 that the output of the AD698 is PULSED ! The pulse length is modified t= o=20 give the temperature compensation. I don't know what the ??designers?? at AD= =20 thought that they were doing. DigiKey list the AD698 DIP version at $70.88.=20= The=20 AD598 does not have this problem, but the DIP version still costs $52.53 for= 1=20 off. The SOIC versions are about half this in small quantities, when stocked= ..=20
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>       You will remember that for m= uch of=20 the two decades I have been using my fully differential
capacitive sens= ors=20 for internal friction research--that the work-horse for that work was the=20 NE5521 chip that is no longer manufactured. Well, I have done a direct=20 comparison of the AD698 with the NE5521 and do not find a great enough=20 performance difference to agree with your claim!  In fact, with the=20 prototype new vertical that I recently built (the details of which I will=20= soon=20 share with list-serve readers), it picked up the Charlotte Is earthquake w= ith=20 this chip, even though the instrument was sitting on a lab bench here in t= he=20 physics building. So I don't think you can make a defensible claim th= at=20 the chip is unsuitable for seismometers. 
    The correction is temperature dependant, so the= re=20 will likely be one temperature at which the correction is zero, presumably a= t=20 one end of the range.
    If you digitise the output directly, you will g= et=20 an uncompensated signal and occasional glitches due to the variable zero=20 output periods. To get the compensated output you need to provide a low= =20 pass filter to integrate the signal. This may slow up the response if you wa= nt=20 to get low noise.
    Trying to use a chip with a stepped level=20 output in a low noise application seems to be 'simply buying=20 trouble'. I am quite happy to avoid using it, particulaly when I can ma= ke=20 up a good detector for a small fraction of the cost. http://www.keckec.com/seismo/ <= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Insofar=20 as expense is concerned, the webpage I recently viewed at Analog Devices=20 indicates a price of about $25 (straight from the companry) for the versio= n=20 that I would use (in large quantities).  I haven't enquired about sin= gle=20 chip prices, although I know from Larry Cochrane that if bought from some=20= of=20 the 'distributors' it is indeed hideously expensive. They love to mark-up=20 units, evidently in this case by a huge amount.
    You might cross check those prices again? The=20 ''low'' AD website price I saw quoted was for the PLCC version in 1,000 off=20 quantities. The 15 off price for the DIP version is $60.
    
    Regards,
 
    Chris
Subject: Re: Shadow Zone From: ChrisAtUpw@....... Date: Sun, 20 Jan 2008 23:02:39 EST In a message dated 20/01/2008, rpratt@............. writes: I see the shadow zone has a range of definitions from 102 to 105 as beginning and 140 to 142 as ending depending on the reference. Is there a most accepted range or is it somewhat dependent on location? Is it a sharp cutoff or a gradual reduction over a few degrees? Hi Randy, The shadow zone is due to the large dense core of the Earth 'shadowing' the signal transmission. The core refracts P waves, but it will not transmit S waves directly. You also get some variation due to the depth of the quake. The cut off is gradual. Regards, Chris Chapman
In a message dated 20/01/2008, rpratt@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I see the shadow zone has a range of definitions fro= m 102 to=20 105 as beginning and 140 to 142 as ending depending on the reference. = ; Is=20 there a most accepted range or is it somewhat dependent on location? = Is=20 it a sharp cutoff or a gradual reduction over a few=20 degrees?
Hi Randy,
 
    The shadow zone is due to the large dense core=20= of=20 the Earth 'shadowing' the signal transmission. The core refracts P waves, bu= t it=20 will not transmit S waves directly. You also get some variation due to the d= epth=20 of the quake. The cut off is gradual.
 
    Regards,
 
    Chris Chapman
Subject: Re: Shadow Zone- Inner Core too From: "Jim ODonnell" geophysics@.......... Date: Mon, 21 Jan 2008 05:56:43 GMT Randy- Until Chris mentioned it I had forgotten about Inge Lehmann, who = I once met at UCBerkeley when she was visiting Prof Perry Byerly. See http://www.amnh.org/education/resources/rfl/web/essaybooks/earth/p_l= ehmann.html Jim O'Donnell = Geological/Geophysical Consultant GEOTECHNICAL APPLICATIONS 702.293.5664 geophysics@.......... 702.281.9081 cell jimo17@........ -- "Randy" wrote: The 1 NM per minute of latitude conversion is where I started as that is= what we used when I was flying. I see the shadow zone has a range of d= efinitions from 102 to 105 as beginning and 140 to 142 as ending dependi= ng on the reference. Is there a most accepted range or is it somewhat d= ependent on location? Is it a sharp cutoff or a gradual reduction over = a few degrees? Randy

Randy- Until Chris mentioned it I had forgotten about Inge Lehm= ann, who I once met at UCBerkeley when she was visiting Prof Perry Byerl= y.

See http://www.amnh.org/education/resources/rfl/w= eb/essaybooks/earth/p_lehmann.html




         &nb= sp;        Jim O'Donnell  &= nbsp;  
        Geo= logical/Geophysical Consultant
      &n= bsp;    GEOTECHNICAL APPLICATIONS
702.293.5664 &n= bsp;  geophysics@..........
702.281.9081 cell   j= imo17@........

-- "Randy" <rpratt@.............> wrote:
=

The 1 NM per minute of latitude convers= ion is where I started as that is what we used when I was flying.  = I see the shadow zone has a range of definitions from 102 to 105 as begi= nning and 140 to 142 as ending depending on the reference.  Is ther= e a most accepted range or is it somewhat dependent on location?  I= s it a sharp cutoff or a gradual reduction over a few degrees?
 
Randy
Subject: Specs for Lehman type sensor From: jonfr@......... Date: Mon, 21 Jan 2008 13:32:24 -0500 (EST) Hi all I am looking for specs for Lehman type sensor. As I can build a lehman type sensor in my school with an help. However, the specs I already aren't good, so I need better onces. If someone has them ready. If no one has them, I need to write them up my self. I need the size and length in cm. I also need a suggestion for the material needed for the mass, I was thinking about using led. But I don't know how good idea that is. For the base of the sensor I was thinking about using aluminum. Please send this to my main email address, jonfr [at] jonfr.com Thanks in advance. Regards. Jón Frímann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Specs for Lehman type sensor From: ChrisAtUpw@....... Date: Mon, 21 Jan 2008 20:42:55 EST In a message dated 21/01/2008 18:32:46 GMT Standard Time, jonfr@......... writes: I am looking for specs for Lehman type sensor. As I can build a Lehman type sensor in my school with help. However, the specs I already aren't good, so I need better ones. If someone has them ready. If no one has them, I need to write them up my self. I need the size and length in cm. I also need a suggestion for the material needed for the mass, I was thinking about using led. But I don't know how good idea that is. For the base of the sensor I was thinking about using aluminum. Please send this to my main email address, jonfr [at] jonfr.com Hi Jon, I use 3" x 1" U channel Al with 1/8" thick Al corner plates for the frame. The arm is about 24" long overall. You want a natural pendulum length of at least 1.5 seconds, 22". If you make it shorter, you may have problems getting a final 20 second period. Have a look our school seismometer at _http://www.bgs.ac.uk/education/school_seismology/seismometer.html_ (http://www.bgs.ac.uk/education/school_seismology/seismometer.html) and _http://jclahr.com/science/psn/chapman/lehman/index.html_ (http://jclahr.com/science/psn/chapman/lehman/index.html) This latter design was modified using a rigid top tube and tungsten carbide rod suspensions, from the SS balls and plates. It is probably easier to use brass for the mass. I make the arm out of 15 mm SS water pipe, but you can also use Al tube. They seem to work well. Regards, Chris Chapman
In a message dated 21/01/2008 18:32:46 GMT Standard Time, jonfr@........ om=20 writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I am=20 looking for specs for Lehman type sensor. As I can build a Lehman type sen= sor=20 in my school with help.

However, the specs I already aren't good, s= o I=20 need better ones. If someone has them ready. If no one has them, I need to= =20 write them up my self.

I need the size and length in cm. I also nee= d a=20 suggestion for the material needed for the mass, I was thinking about usin= g=20 led. But I don't know how good idea that is. For the base of the sensor I=20= was=20 thinking about using aluminum.

Please send this to my main email=20 address, jonfr [at] jonfr.com
Hi Jon,
 
    I use 3" x 1" U channel Al with 1/8" thick Al=20 corner plates for the frame. The arm is about 24" long overall.
    You want a natural pendulum length of at least=20= 1.5=20 seconds, 22". If you make it shorter, you may have problems getting a f= inal=20 20 second period. Have a look our school seismometer at h= ttp://www.bgs.ac.uk/education/school_seismology/seismometer.html an= d=20 http://jcla= hr.com/science/psn/chapman/lehman/index.html This=20 latter design was modified using a rigid top tube and tungsten carbide=20= rod=20 suspensions, from the SS balls and plates. 
    It is probably easier to use brass for the mass= .. I=20 make the arm out of 15 mm SS water pipe, but you can also use Al tube.
    They seem to work well.
 
    Regards,
 
    Chris Chapman
Subject: RE: Specs for Lehman type sensor From: "Steve Hammond" shammon1@............. Date: Mon, 21 Jan 2008 21:43:13 -0800 Hi Jon, Here is a good place to start. http://pw2.netcom.com/~shammon1/equip.htm And here are some photos you = can look at of a Lehman I built to help get you going. http://pw2.netcom.com/~shammon1/AptosStn.htm. And yes, you can use led. Scroll to the bottom of the page in the last URL and you will see the = specs. Regards, Steve Hammond, PSN Aptos, California. -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of jonfr@......... Sent: Monday, January 21, 2008 10:32 AM To: psn-l@.............. Subject: Specs for Lehman type sensor Hi all I am looking for specs for Lehman type sensor. As I can build a lehman = type sensor in my school with an help. However, the specs I already aren't good, so I need better onces. If = someone has them ready. If no one has them, I need to write them up my self. I need the size and length in cm. I also need a suggestion for the = material needed for the mass, I was thinking about using led. But I don't know = how good idea that is. For the base of the sensor I was thinking about using aluminum. Please send this to my main email address, jonfr [at] jonfr.com Thanks in advance. Regards. J=F3n Fr=EDmann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Specs for Lehman type sensor From: jonfr@......... Date: Tue, 22 Jan 2008 14:12:10 -0500 (EST) Hi I am looking for a more advanced design. But this is a old design. I am also wondering what size I should use. I was thinking about 60 cm in length for the arm. 60 cm high and with 20 kg mass in order to get 20 sec period. Please let me know this is good or not. Regards. Jón Frímann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: QUESTION about Slip Faults From: "Jerry Payton" gpayton880@....... Date: Sun, 27 Jan 2008 11:25:45 -0600 Since it is rather slow now, let me throw out a question that I have never had satisfactorily answered to me; directly or reading. Differentiating between a Left Lateral or Right Lateral Slip Fault's movement, the USGS Visual Glossary states: "If you were to stand on the fault and look along its length, this is a type of strike-slip fault where the left block moves toward you and the right block moves away" IF I were to turn around looking the opposite direction the description would change. It is all relative to the direction you are facing. If I assumed that I was always looking North, the answer would work. BUT, not all faults run generally North-South. So, when describing a Right or Left Lateral Slip Fault, how does one know what is being described to them? There must be some "standard" or "point of view" that explains this. Or, does it matter, as long as you realize it IS a slip fault. I have spent some time on archaeological digs near the Dead Sea in Israel. The Dead Sea Rift transverses through there and is described as moving southward on the Israel side and northward on the Jordan side. If I were able to straddle the fault and face North, I could call it a Right Lateral, but the reverse is true if I faced South. Signed: Confused, but not Lost, Jerry
Since it is rather slow now, let me throw out a question that I = have never=20 had satisfactorily answered to me; directly or reading.
 
Differentiating between a Left Lateral or Right Lateral Slip = Fault's=20 movement, the USGS Visual Glossary states: "If you were to stand on the = fault=20 and look along its length, this is a type of strike-slip fault where the = left=20 block moves toward you and the right block moves away"
 
IF I were to turn around looking the opposite direction the = description=20 would change.  It is all relative to the direction you are = facing.  If=20 I assumed that I was always looking North, the answer would work.  = BUT, not=20 all faults run generally North-South.  So, when describing a Right = or Left=20 Lateral Slip Fault, how does one know what is being described to = them? =20 There must be some "standard" or "point of view" that explains = this.  Or,=20 does it matter, as long as you realize it IS a slip fault.
 
I have spent some time on archaeological digs near the Dead = Sea in=20 Israel. The Dead Sea Rift transverses through there and is = described as=20 moving southward on the Israel side and northward on the Jordan = side.  If I=20 were able to straddle the fault and face North, I could call it a Right = Lateral,=20 but the reverse is true if I faced South. 
 
Signed: Confused, but not Lost,
Jerry
 
 
Subject: Re: QUESTION about Slip Faults From: "Jim ODonnell" geophysics@.......... Date: Sun, 27 Jan 2008 17:46:47 GMT Jerry- You do not straddle the fault but stand on 1 side and see the oth= er side go Left or Right; Left lateral fault & Right lateral fault. You= step on the other side and the directions are reversed, so Left is alwa= ys Left, etc, regardless of the strike direction of the fault. = See http://www.abag.ca.gov/bayarea/eqmaps/fixit/ch2/sld003.htm We are talking about Strike slip faults which are mostly horizontal move= ment like the San Andreas fault. Actually, faults usually have both comp= onents Horizontal & Vertical movement. Normal Faults have mostly vertical movement, so you can be on the Up sid= e or Down side. More damage seems to occur on the Down side. Jerry- Can you write me off line so I can hear more about your archeolog= y digs....Jim Jim O'Donnell = Geological/Geophysical Consultant GEOTECHNICAL APPLICATIONS 702.293.5664 geophysics@.......... 702.281.9081 cell jimo17@........ -- "Jerry Payton" wrote: Since it is rather slow now, let me throw out a question that I have nev= er had satisfactorily answered to me; directly or reading. Differentiati= ng between a Left Lateral or Right Lateral Slip Fault's movement, the US= GS Visual Glossary states: "If you were to stand on the fault and look a= long its length, this is a type of strike-slip fault where the left bloc= k moves toward you and the right block moves away" IF I were to turn aro= und looking the opposite direction the description would change. It is = all relative to the direction you are facing. If I assumed that I was a= lways looking North, the answer would work. BUT, not all faults run gen= erally North-South. So, when describing a Right or Left Lateral Slip Fa= ult, how does one know what is being described to them? There must be s= ome "standard" or "point of view" that explains this. Or, does it matte= r, as long as you realize it IS a slip fault. I have spent some time on = archaeological digs near the Dead Sea in Israel. The Dead Sea Rift trans= verses through there and is described as moving southward on the Israel = side and northward on the Jordan side. If I were able to straddle the f= ault and face North, I could call it a Right Lateral, but the reverse is= true if I faced South. Signed: Confused, but not Lost,Jerry

Jerry- You do not straddle the fault but stand on 1 side and se= e the other side go Left or Right; Left lateral fault & Right latera= l fault.  You step on the other side and the directions are reverse= d, so Left is always Left, etc, regardless of the strike direction = of the fault.
See http://www.abag.ca.gov/bayarea/eqmaps/fixit/ch2/sld= 003.htm

We are talking about Strike slip faults which are mostly horizontal m= ovement like the San Andreas fault. Actually, faults usually have b= oth components Horizontal & Vertical movement.
Normal Faults= have mostly vertical movement, so you can be on the Up side or Down sid= e.  More damage seems to occur on the Down side.

Jerry- Can = you write me off line so I can hear more about your archeology digs....J= im

          &n= bsp;       Jim O'Donnell   =   
        Geologic= al/Geophysical Consultant
       &= nbsp;   GEOTECHNICAL APPLICATIONS
702.293.5664  &= nbsp; geophysics@..........
702.281.9081 cell   jimo17= @........

-- "Jerry Payton" <gpayton880@.......> wrote:
=

Since it is rather slow now, let me throw out a question that I hav= e never had satisfactorily answered to me; directly or reading.
 
Differentiating between a Left Lateral or Right Lateral Slip F= ault's movement, the USGS Visual Glossary states: "If you were to stand = on the fault and look along its length, this is a type of strike-slip fa= ult where the left block moves toward you and the right block moves away= "
 
IF I were to turn around looking the opposite direction the descrip= tion would change.  It is all relative to the direction you are fac= ing.  If I assumed that I was always looking North, the answer woul= d work.  BUT, not all faults run generally North-South.  So, w= hen describing a Right or Left Lateral Slip Fault, how does one know wha= t is being described to them?  There must be some "standard" or "po= int of view" that explains this.  Or, does it matter, as long as yo= u realize it IS a slip fault.
 
I have spent some time on archaeological digs near the Dead Se= a in Israel. The Dead Sea Rift transverses through there and is des= cribed as moving southward on the Israel side and northward on the Jorda= n side.  If I were able to straddle the fault and face North, I cou= ld call it a Right Lateral, but the reverse is true if I faced South.&nb= sp;
 
Signed: Confused, but not Lost,
Jerry
 
 
Subject: Re: QUESTION about Slip Faults From: "Jerry Payton" gpayton880@....... Date: Sun, 27 Jan 2008 12:01:00 -0600 Jerry- You do not straddle the fault but stand on 1 side and see the other side go Left or Right; Left lateral fault & Right lateral fault. I think we are saying the same thing. I was quoting the USGS site: http://earthquake.usgs.gov/learning/glossary.php?term=left-lateral My confusion is HOW to accurately communicate to someone else about a particular fault. If I said it was "right-lateral", how would the other person visualize what I was saying? Describing a Normal Fault, one would give the Strike, Dip and etc. The person then could visualize the whole thing. Maybe, I am just over emphasizing a point? (My email is gpayton@....... if you want to talk about the digs.........) Jerry
Jerry- You do not straddle the fault but stand on 1 side and see = the other=20 side go Left or Right; Left lateral fault & Right lateral = fault. =20
 
I think we are saying the same thing.  I was quoting = the USGS=20 site:  http://earthquake.usgs.gov/learning/glossary.php?term=3Dleft-lateral=
 
My confusion is HOW to accurately = communicate to=20 someone else about a particular fault.  If I said it was = "right-lateral",=20 how would the other person visualize what I was saying?  Describing = a=20 Normal Fault, one would give the Strike, Dip and etc.  The person = then=20 could visualize the whole thing.  Maybe, I am just over emphasizing = a=20 point?
 
(My email is gpayton@....... = if you=20 want to talk about the digs.........)
 
Jerry
Subject: Re: QUESTION about Slip Faults From: Stephen & Kathy skmort@............ Date: Sun, 27 Jan 2008 11:27:46 -0800 It doesn't matter which scenario you pick, (watching the opposite block from east, or west, or straddling the fault facing north, or south), the relative motion to the body will always be the same. The opposite block will move left, or the block on the left side will move toward you. Changing the way you face doesn't matter. A very simple test. Get two pieces of paper lay them side by side. draw arrows for the direction you want them to move relative to each other. Stand on one, face the other and move it in the direction of its arrow,, then stand on the other paper, face the original and move it in the direction of its arrow. Notice, they both moved the same relative to your body,, left for a left lateral fault. Now straddle, put one paper in front of each foot. Notice the left paper arrow is pointing toward you,, go to the opposite side of the paper and face the opposite direction,, the arrow on the left paper, (the other paper) is still pointing toward you. This is literally what I had to do to get it through my simple mind. Stephen PSN Station #55 Jerry Payton wrote: > Jerry- You do not straddle the fault but stand on 1 side and see the > other side go Left or Right; Left lateral fault & Right lateral fault. > > *I think we are saying the same thing. I was quoting the USGS site: > http://earthquake.usgs.gov/learning/glossary.php?term=left-lateral* > ** > *My confusion is* *HOW to accurately communicate to someone else about > a particular fault. If I said it was "right-lateral", how would the > other person visualize what I was saying? Describing a Normal Fault, > one would give the Strike, Dip and etc. The person then could > visualize the whole thing. Maybe, I am just over emphasizing a point?* > > (My email is gpayton@....... if you want to > talk about the digs.........) > > *Jerry* It doesn't matter which scenario you pick, (watching the opposite block from east, or west, or straddling the fault facing north, or south), the relative motion to the body will always be the same.=A0 The opposite block will move left, or the block on= the left side will move toward you.=A0 Changing the way you face doesn't matter.=A0 A very simple test.=A0 Get two pieces of paper lay them side b= y side.=A0 draw arrows for the direction you want them to move relative to each other.=A0 Stand on one, face the other and move it in the direction of its arrow,, then stand on the other paper, face the original and move it in the direction of its arrow.=A0 Notice, they both moved the same relative to your body,,=A0=A0 left for a left lateral fault.=A0 Now straddle, put one paper in front of each foot.=A0 Notice the left paper arrow is pointing toward you,,=A0 go to the opposite side of the paper and face the opposite direction,,=A0 the arrow on the left paper, (the other paper) is still pointing toward you.=A0=A0 This is literally what I= had to do to get it through my simple mind.
=A0 Stephen
=A0 PSN Station #55

Jerry Payton wrote:
Jerry- You do not straddle the fault but stand on 1 side and see the other side go Left or Right; Left lateral fault & Right lateral fault.=A0
=A0
I think we are saying the same thing.=A0 I was quoting the= USGS site:=A0 http://earthquake.usgs.gov/learning/glossary.php?term=3Dleft-latera= l
=A0
My confusion is HOW to accurately communicate to someone else about a particular fault.=A0 If I said it was= "right-lateral", how would the other person visualize what I was saying?=A0 Describing a Normal Fault, one would give the Strike, Dip and etc.=A0 The person then could visualize the whole thing.=A0 Maybe, I am just over emphasizing a point?
=A0
=A0
Jerry
Subject: Re: QUESTION about Slip Faults From: "Jerry Payton" gpayton880@....... Date: Sun, 27 Jan 2008 13:35:41 -0600 Thanks a million! Now, I think I understand. It is the relative movement of the "opposite" block that determines the description. Soooo simple. Regards, Jerry ----- Original Message ----- From: Stephen & Kathy To: psn-l@.............. Sent: Sunday, January 27, 2008 1:27 PM Subject: Re: QUESTION about Slip Faults It doesn't matter which scenario you pick, (watching the opposite block from east, or west, or straddling the fault facing north, or south), the relative motion to the body will always be the same. The opposite block will move left, or the block on the left side will move toward you. Changing the way you face doesn't matter. A very simple test. Get two pieces of paper lay them side by side. draw arrows for the direction you want them to move relative to each other. Stand on one, face the other and move it in the direction of its arrow,, then stand on the other paper, face the original and move it in the direction of its arrow. Notice, they both moved the same relative to your body,, left for a left lateral fault. Now straddle, put one paper in front of each foot. Notice the left paper arrow is pointing toward you,, go to the opposite side of the paper and face the opposite direction,, the arrow on the left paper, (the other paper) is still pointing toward you. This is literally what I had to do to get it through my simple mind. Stephen PSN Station #55 Jerry Payton wrote: Jerry- You do not straddle the fault but stand on 1 side and see the other side go Left or Right; Left lateral fault & Right lateral fault. I think we are saying the same thing. I was quoting the USGS site: http://earthquake.usgs.gov/learning/glossary.php?term=left-lateral My confusion is HOW to accurately communicate to someone else about a particular fault. If I said it was "right-lateral", how would the other person visualize what I was saying? Describing a Normal Fault, one would give the Strike, Dip and etc. The person then could visualize the whole thing. Maybe, I am just over emphasizing a point? (My email is gpayton@....... if you want to talk about the digs.........) Jerry
Thanks a million!  Now, I think I understand.  It is the = relative=20 movement of the "opposite" block that determines the description.  = Soooo=20 simple.
Regards,
Jerry
 
 
----- Original Message -----=20
Sent: Sunday, January 27, 2008 1:27 PM
Subject: Re: QUESTION about Slip Faults

It doesn't matter which scenario you = pick,=20 (watching the opposite block from east, or west, or straddling the fault = facing=20 north, or south), the relative motion to the body will always be the = same. =20 The opposite block will move left, or the block on the left side will = move=20 toward you.  Changing the way you face doesn't matter.  A very = simple=20 test.  Get two pieces of paper lay them side by side.  draw = arrows for=20 the direction you want them to move relative to each other.  Stand = on one,=20 face the other and move it in the direction of its arrow,, then stand on = the=20 other paper, face the original and move it in the direction of its = arrow. =20 Notice, they both moved the same relative to your body,,   = left for a=20 left lateral fault.  Now straddle, put one paper in front of each=20 foot.  Notice the left paper arrow is pointing toward you,,  = go to the=20 opposite side of the paper and face the opposite direction,,  the = arrow on=20 the left paper, (the other paper) is still pointing toward = you.   This=20 is literally what I had to do to get it through my simple = mind.
 =20 Stephen
  PSN Station #55

Jerry Payton = wrote:=20
Jerry- You do not straddle the fault but stand on 1 side and see = the=20 other side go Left or Right; Left lateral fault & Right lateral=20 fault. 
 
I think we are saying the same thing.  I was quoting = the=20 USGS site:  http://earthquake.usgs.gov/learning/glossary.php?term=3Dleft-lateral=
 
My confusion is HOW to accurately = communicate to=20 someone else about a particular fault.  If I said it was = "right-lateral",=20 how would the other person visualize what I was saying?  = Describing a=20 Normal Fault, one would give the Strike, Dip and etc.  The person = then=20 could visualize the whole thing.  Maybe, I am just over = emphasizing a=20 point?
 
(My email is gpayton@....... if you=20 want to talk about the digs.........)
 
Jerry
Subject: Re: QUESTION about Slip Faults From: Stephen & Kathy skmort@............ Date: Sun, 27 Jan 2008 12:11:14 -0800 At least that is the way I understand it. It doesn't matter if the block on the other side doesn't move and the one you are standing on moves right, it is still a left lateral fault. Corrections to my understanding are of course always welcome. Stephen Station #55 Jerry Payton wrote: > Thanks a million! Now, I think I understand. It is the relative > movement of the "opposite" block that determines the description. > Soooo simple. > Regards, > Jerry > > > ----- Original Message ----- > *From:* Stephen & Kathy > *To:* psn-l@.............. > *Sent:* Sunday, January 27, 2008 1:27 PM > *Subject:* Re: QUESTION about Slip Faults > > It doesn't matter which scenario you pick, (watching the opposite > block from east, or west, or straddling the fault facing north, or > south), the relative motion to the body will always be the same. The > opposite block will move left, or the block on the left side will move > toward you. Changing the way you face doesn't matter. A very simple > test. Get two pieces of paper lay them side by side. draw arrows for > the direction you want them to move relative to each other. Stand on > one, face the other and move it in the direction of its arrow,, then > stand on the other paper, face the original and move it in the > direction of its arrow. Notice, they both moved the same relative to > your body,, left for a left lateral fault. Now straddle, put one > paper in front of each foot. Notice the left paper arrow is pointing > toward you,, go to the opposite side of the paper and face the > opposite direction,, the arrow on the left paper, (the other paper) > is still pointing toward you. This is literally what I had to do to > get it through my simple mind. > Stephen > PSN Station #55 > > Jerry Payton wrote: >> Jerry- You do not straddle the fault but stand on 1 side and see the >> other side go Left or Right; Left lateral fault & Right lateral fault. >> >> *I think we are saying the same thing. I was quoting the USGS site: >> http://earthquake.usgs.gov/learning/glossary.php?term=left-lateral* >> ** >> *My confusion is* *HOW to accurately communicate to someone else >> about a particular fault. If I said it was "right-lateral", how >> would the other person visualize what I was saying? Describing a >> Normal Fault, one would give the Strike, Dip and etc. The person >> then could visualize the whole thing. Maybe, I am just over >> emphasizing a point?* >> >> (My email is gpayton@....... if you want to >> talk about the digs.........) >> >> *Jerry* At least that is the way I understand it.=A0 It doesn't matter if the block on the other side doesn't move and the one you are standing on moves right, it is still a left lateral fault.=A0=A0 Corrections to my understanding are of course always welcome.
=A0 Stephen
=A0 Station #55

Jerry Payton wrote:
Thanks a million!=A0 Now, I think I understand.=A0 It is the relative movement of the "opposite" block that determines the description.=A0 Soooo simple.
Regards,
Jerry
=A0
=A0
----- Original Message -----
Sent: Sunday, January 27, 2008 1:27 PM
Subject: Re: QUESTION about Slip Faults

It doesn't matter which scenario you pick, (watching the opposite block from east, or west, or straddling the fault facing north, or south), the relative motion to the body will always be the same.=A0 The opposite block will move left, or the block on= the left side will move toward you.=A0 Changing the way you face doesn't matter.=A0 A very simple test.=A0 Get two pieces of paper lay them side b= y side.=A0 draw arrows for the direction you want them to move relative to each other.=A0 Stand on one, face the other and move it in the direction of its arrow,, then stand on the other paper, face the original and move it in the direction of its arrow.=A0 Notice, they both moved the same relative to your body,,=A0=A0 left for a left lateral fault.=A0 Now straddle, put one paper in front of each foot.=A0 Notice the left paper arrow is pointing toward you,,=A0 go to the opposite side of the paper and face the opposite direction,,=A0 the arrow on the left paper, (the other paper) is still pointing toward you.=A0=A0 This is literally what I= had to do to get it through my simple mind.
=A0 Stephen
=A0 PSN Station #55

Jerry Payton wrote:
Jerry- You do not straddle the fault but stand on 1 side and see the other side go Left or Right; Left lateral fault & Right lateral fault.=A0
=A0
I think we are saying the same thing.=A0 I was quoting the USGS site:=A0 http://earthquake.usgs.gov/learning/glossary.php?term=3Dleft-latera= l
=A0
My confusion is HOW to accurately communicate to someone else about a particular fault.=A0 If I said it was= "right-lateral", how would the other person visualize what I was saying?=A0 Describing a Normal Fault, one would give the Strike, Dip and etc.=A0 The person then could visualize the whole thing.=A0 Maybe, I am just over emphasizing a point?
=A0
=A0
Jerry
Subject: Re: QUESTION about Slip Faults From: "Thomas Dick" dickthomas01@............. Date: Sun, 27 Jan 2008 14:29:19 -0600 will the "p" wave created by movement along a strike-slip fault be = distinct from other types?
will the "p" wave created by movement = along a=20 strike-slip fault be distinct from other = types?
Subject: Re: QUESTION about Slip Faults From: "Jerry Payton" gpayton880@....... Date: Sun, 27 Jan 2008 17:59:06 -0600 Thomas, I suspect that the body and surface waves are NOT different from any other EQ's; since, it is still basically a release of elastic tension. I would think that regardless if it were a upward, downward, sideward's movement. Te amount of stored energy would be the same depending upon the rock enviroment and intensity of the quake. That's my 2 cents. I'm sure that there are people here more qualified than me to answer that. Jerry ----- Original Message ----- From: Thomas Dick To: psn-l@.............. Sent: Sunday, January 27, 2008 2:29 PM Subject: Re: QUESTION about Slip Faults will the "p" wave created by movement along a strike-slip fault be distinct from other types?
Thomas, I suspect that the body and surface waves are NOT = different=20 from any other EQ's; since, it is still basically a release of elastic=20 tension.  I would think that regardless if it were a upward, = downward,=20 sideward's movement.  Te amount of stored energy would be the = same=20 depending upon the rock enviroment and intensity of the quake.  = That's my 2=20 cents.
 
I'm sure that there are people here more qualified than me to = answer=20 that.
 
Jerry 
 
 
----- Original Message -----=20
Sent: Sunday, January 27, 2008 2:29 PM
Subject: Re: QUESTION about Slip Faults

will the "p" wave created by movement = along a=20 strike-slip fault be distinct from other = types?
Subject: Re: QUESTION about Slip Faults From: John Lahr johnjan@........ Date: Sun, 27 Jan 2008 19:12:50 -0800 Hi Thomas, The sense (polarity) of motion of the phases recorded at a seismic station can be used, when combined with many other stations, to determine the focal mechanism of the earthquake. Here's a web site where an explanation is attempted. http://quake.usgs.gov/recenteqs/beachball.html Cheers, John At 12:29 PM 1/27/2008, Thomas Dick wrote: >will the "p" wave created by movement along a strike-slip fault be >distinct from other types? __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: QUESTION about Slip Faults From: "Thomas Dick" dickthomas01@............. Date: Mon, 28 Jan 2008 08:57:05 -0600 > > The sense (polarity) of motion of the phases recorded at a seismic station > can be used, I thought that sometimes the strike-slip as being like dragging a bow acrossed a violin string as the sides of the fault "bounce" along while the reverse and normal faulting are more like to being like breaking a limb off a tree. I thought I had seen some "stepping" of P on some of the earthquakes off the west coast...my imagination? __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Interesting article From: Pete Rowe ptrowe@......... Date: Tue, 29 Jan 2008 08:30:22 -0800 (PST) There is still so much to learn... http://www.sciencedaily.com/releases/2008/01/080124145022.htm Pete ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Interesting article From: "Jerry Payton" gpayton880@....... Date: Tue, 29 Jan 2008 11:05:06 -0600 Yes, Pete, that is an interesting theory. I wonder what is the "electrical" component of an earthquake that is measured by a seismograph? I thought all the seismic waves were physical movements. Comments out there?? Jerry ----- Original Message ----- From: Pete Rowe To: psn-l Sent: Tuesday, January 29, 2008 10:30 AM Subject: Interesting article There is still so much to learn... http://www.sciencedaily.com/releases/2008/01/080124145022.htm Pete ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Yes, Pete, that is an interesting theory.  I wonder what is = the=20 "electrical" component of an earthquake that is measured by a = seismograph? =20 I thought all the seismic waves were physical movements.  Comments = out=20 there??
Jerry
 
 
----- Original Message -----=20
From: Pete Rowe =
To: psn-l
Sent: Tuesday, January 29, 2008 10:30 AM
Subject: Interesting article

There is still so much to learn...

ht= tp://www.sciencedaily.com/releases/2008/01/080124145022.htm

Pete


     =20 _________________________________________________________________________= ___________
Never=20 miss a thing.  Make Yahoo your home page.
http://www.yahoo.com/r/hs
_____= _____________________________________________________

Public=20 Seismic Network Mailing List (PSN-L)

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Subject: Re: Interesting article From: ChrisAtUpw@....... Date: Tue, 29 Jan 2008 20:59:18 EST In a message dated 29/01/2008, gpayton880@....... writes: Yes, Pete, that is an interesting theory. I wonder what is the "electrical" component of an earthquake that is measured by a seismograph? I thought all the seismic waves were physical movements. Comments out there? Hi Jerry, Note that the depths concerned are from 400 to 1800 miles - deeper than most earthquake sources. The para-magnetic properties of the iron compounds vary. You are unlikely to see electrical effects at the surface due to this, although there may be other surface electrical / magnetic effects. Seismometers do not measure changes in potential or magnetic fields, only physical movements. Regards, Chris Chapman
In a message dated 29/01/2008, gpayton880@....... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Yes,=20 Pete, that is an interesting theory.  I wonder what is the "electrica= l"=20 component of an earthquake that is measured by a seismograph?  I thou= ght=20 all the seismic waves were physical movements.  Comments out=20 there?
Hi Jerry,
 
    Note that the depths concerned are from 400 to=20= 1800=20 miles - deeper than most earthquake sources. The para-magnetic properti= es=20 of the iron compounds vary. You are unlikely to see electrical effects at th= e=20 surface due to this, although there may be other surface electrical / magnet= ic=20 effects. Seismometers do not measure changes in potential or magnetic fields= ,=20 only physical movements.
 
    Regards,
 
    Chris Chapman
Subject: Re: Interesting article From: "Geoff" gmvoeth@........... Date: Wed, 30 Jan 2008 03:25:28 -0700 All it says is that they modled in a lab a phenomena that seems to be real and the seismic modle should be re-calculated or reprogrammed to include this phenomena When there exists an intense velocity change it is like turning into a mirror and will reflect or refract waves more intensely in that region just outside the liquid outer core sort of like an increase in the index of refraction or so I understand. They do not say to me HOW this electrical phenomena actually causes the effect only that it is associated with it. Regards; geoff ----- Original Message ----- From: To: Sent: Tuesday, January 29, 2008 6:59 PM Subject: Re: Interesting article > > In a message dated 29/01/2008, gpayton880@....... writes: > > Yes, Pete, that is an interesting theory. I wonder what is the "electrical" > component of an earthquake that is measured by a seismograph? I thought > all the seismic waves were physical movements. Comments out there? > > > Hi Jerry, > > Note that the depths concerned are from 400 to 1800 miles - deeper than > most earthquake sources. The para-magnetic properties of the iron compounds > vary. You are unlikely to see electrical effects at the surface due to this, > although there may be other surface electrical / magnetic effects. > Seismometers do not measure changes in potential or magnetic fields, only physical > movements. > > Regards, > > Chris Chapman > > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Comparison of available seismometers From: "K.-Benoit Evans" kevans@............ Date: Wed, 30 Jan 2008 21:52:22 -0500 I am interested in acquiring a simple seismometer package for amateur=20 use that is sensitive enough to detect teleseismic events. I would like=20= to acquire a ready-to-use instrument rather than build something from=20 scratch or from a kit. My main question is which seismometer to buy. I=20= have come across the following instruments on the Web: AS-1 Amateur Seismologist (Jeff Batten) $550 ??? http://www.amateurseismologist.com Vertical School Seismometer Ward=92s Natural Science $500 http://www.wardsci.com/Product.asp_Q_cmss_E_seismometer_A_pn_E_IG0018602 EQ-1 Next Generation Science $600 http://www.nexgensci.com/store/pc/viewPrd.asp?idproduct=3D1 Volksmeter II RLL Instruments (Zoltech) $995 single channel, $1495=20= dual channel (patented Symmetric Differential Capacitor (SDC) array sensor) http://www.rllinstruments.com In spite of the price difference, the Volksmeter seems interesting. As=20= far as I an tell, it is based on recent technology that is different=20 form the other three, which seem to be of the traditional Lehman type. Does anyone have any opinions or advice to give a rank beginner who has=20= not been in a science classroom or lab in over 40 years? Regards, Beno=EEt Evans Qu=E9bec, Canada= I am interested in acquiring a simple seismometer package for amateur use that is sensitive enough to detect teleseismic events. I would like to acquire a ready-to-use instrument rather than build something from scratch or from a kit. My main question is which seismometer to buy. I have come across the following instruments on the Web: AS-1 Amateur Seismologist (Jeff Batten) $550 ??? http://www.amateurseismologist.com Vertical School Seismometer Ward=92s Natural Science $500 http://www.wardsci.com/Product.asp_Q_cmss_E_seismometer_A_pn_E_IG0018602 EQ-1 Next Generation Science $600 http://www.nexgensci.com/store/pc/viewPrd.asp?idproduct=3D1 Volksmeter II RLL Instruments (Zoltech) $995 single channel, $1495 dual channel (patented Symmetric Differential Capacitor (SDC) array sensor) http://www.rllinstruments.com In spite of the price difference, the Volksmeter seems interesting. As far as I an tell, it is based on recent technology that is different form the other three, which seem to be of the traditional Lehman type. Does anyone have any opinions or advice to give a rank beginner who has not been in a science classroom or lab in over 40 years? Regards, Beno=EEt Evans Qu=E9bec, Canada= Subject: Re: Your message to the psn-l mailing list From: "K.-Benoit Evans" kevans@............ Date: Wed, 30 Jan 2008 22:45:06 -0500 One minute after receiving the following message, I received another =20 one saying my message had been bounced as spam. Can you get this =20 message to the list? Your spam filter is too strong. I have been =20 sending e-mail regularly for 20 years and this is the first message of =20= mine that has ever been bounced in this way. On 30 Jan 2008, at 21:52, postmaster@.............. wrote: > The attached message has been sent to the psn-l mail list. > > From: "K.-Benoit Evans" > Date: 30 January 2008 21:52:22 EST > To: PSN-L@.............. > Subject: Comparison of available seismometers > Reply-To: psn-l@.............. > > > I am interested in acquiring a simple seismometer package for amateur =20= > use that is sensitive enough to detect teleseismic events. I would =20 > like to acquire a ready-to-use instrument rather than build something =20= > from scratch or from a kit. My main question is which seismometer to =20= > buy. I have come across the following instruments on the Web: > > AS-1 Amateur Seismologist (Jeff Batten) $550 ??? > http://www.amateurseismologist.com > > Vertical School Seismometer Ward=92s Natural Science $500 > http://www.wardsci.com/=20 > Product.asp_Q_cmss_E_seismometer_A_pn_E_IG0018602 > > EQ-1 Next Generation Science $600 > http://www.nexgensci.com/store/pc/viewPrd.asp?idproduct=3D1 > > Volksmeter II RLL Instruments (Zoltech) $995 single channel, =20 > $1495 dual channel > (patented Symmetric Differential Capacitor (SDC) array sensor) > http://www.rllinstruments.com > > In spite of the price difference, the Volksmeter seems interesting. As = =20 > far as I an tell, it is based on recent technology that is different =20= > form the other three, which seem to be of the traditional Lehman type. > > Does anyone have any opinions or advice to give a rank beginner who =20= > has not been in a science classroom or lab in over 40 years? > > > Regards, > > Beno=EEt Evans > Qu=E9bec, Canada > > Regards, Beno=EEt Evans One minute after receiving the following message, I received another one saying my message had been bounced as spam. Can you get this message to the list? Your spam filter is too strong. I have been sending e-mail regularly for 20 years and this is the first message of mine that has ever been bounced in this way. On 30 Jan 2008, at 21:52, postmaster@.............. wrote: The attached message has been sent to the psn-l mail list. = Helvetica0000,0000,0000 From: = Helvetica"K.-Benoit= Evans" < 0000,0000,0000Date: 30 January 2008 21:52:22 EST 0000,0000,0000To: PSN-L@.............. 0000,0000,0000Subject: Comparison of available seismometers 0000,0000,0000Reply-To: psn-l@.............. I am interested in acquiring a simple seismometer package for amateur use that is sensitive enough to detect teleseismic events. I would like to acquire a ready-to-use instrument rather than build something from scratch or from a kit. My main question is which seismometer to buy. I have come across the following instruments on the Web: AS-1 Amateur Seismologist (Jeff Batten) $550 ??? http://www.amateurseismologist.com Vertical School Seismometer Ward=92s Natural Science $500 http://www.wardsci.com/Product.asp_Q_cmss_E_seismometer_A_pn_E_IG0018602 EQ-1 Next Generation Science $600 http://www.nexgensci.com/store/pc/viewPrd.asp?idproduct=3D1 Volksmeter II RLL Instruments (Zoltech) $995 single channel, $1495 dual channel (patented Symmetric Differential Capacitor (SDC) array sensor) http://www.rllinstruments.com In spite of the price difference, the Volksmeter seems interesting. As far as I an tell, it is based on recent technology that is different form the other three, which seem to be of the traditional Lehman type. Does anyone have any opinions or advice to give a rank beginner who has not been in a science classroom or lab in over 40 years? Regards, Beno=EEt Evans Qu=E9bec, Canada Regards, Beno=EEt Evans Subject: Re: Comparison of available seismometers From: "Les LaZar" llazar@.................. Date: Wed, 30 Jan 2008 23:01:28 -0800 Hello Benoit, I am the project engineer for the VolksMeter. I would be happy to = answer any questions you have on the VolksMeter. Regards, Les LaZar RLL Instruments / a division of Zoltech Corporation ----- Original Message -----=20 From: K.-Benoit Evans=20 To: PSN-L@................. Sent: Wednesday, January 30, 2008 6:52 PM Subject: Comparison of available seismometers I am interested in acquiring a simple seismometer package for amateur = use that is sensitive enough to detect teleseismic events. I would like = to acquire a ready-to-use instrument rather than build something from = scratch or from a kit. My main question is which seismometer to buy. I = have come across the following instruments on the Web: AS-1 Amateur Seismologist (Jeff Batten) $550 ??? http://www.amateurseismologist.com Vertical School Seismometer Ward=92s Natural Science $500 = http://www.wardsci.com/Product.asp_Q_cmss_E_seismometer_A_pn_E_IG0018602 EQ-1 Next Generation Science $600 http://www.nexgensci.com/store/pc/viewPrd.asp?idproduct=3D1 Volksmeter II RLL Instruments (Zoltech) $995 single channel, $1495 = dual channel (patented Symmetric Differential Capacitor (SDC) array sensor) http://www.rllinstruments.com In spite of the price difference, the Volksmeter seems interesting. As = far as I an tell, it is based on recent technology that is different = form the other three, which seem to be of the traditional Lehman type. Does anyone have any opinions or advice to give a rank beginner who = has not been in a science classroom or lab in over 40 years? Regards, Beno=EEt Evans Qu=E9bec, Canada
Hello Benoit,
 
I am the project engineer for the = VolksMeter. =20 I would be happy to answer any questions you have on the=20 VolksMeter.
 
Regards,
 
Les LaZar
RLL Instruments / a division of Zoltech = Corporation
----- Original Message -----
From:=20 K.-Benoit=20 Evans
Sent: Wednesday, January 30, = 2008 6:52=20 PM
Subject: Comparison of = available=20 seismometers

I am interested in acquiring a simple seismometer = package for=20 amateur use that is sensitive enough to detect teleseismic events. I = would=20 like to acquire a ready-to-use instrument rather than build something = from=20 scratch or from a kit. My main question is which seismometer to buy. I = have=20 come across the following instruments on the Web:

AS-1 Amateur=20 Seismologist (Jeff Batten) $550=20 ???
http://www.amateurseismologist.com

Vertical School = Seismometer=20 Ward=92s Natural Science=20 = $500
http://www.wardsci.com/Product.asp_Q_cmss_E_seismometer_A_pn_E_IG= 0018602

EQ-1=20 Next Generation Science=20 = $600
http://www.nexgensci.com/store/pc/viewPrd.asp?idproduct=3D1
Volksmeter=20 II RLL Instruments (Zoltech) $995 single channel, $1495 dual=20 channel
(patented Symmetric Differential Capacitor (SDC) array=20 sensor)
http://www.rllinstruments.com

In spite of the price=20 difference, the Volksmeter seems interesting. As far as I an tell, it = is based=20 on recent technology that is different form the other three, which = seem to be=20 of the traditional Lehman type.

Does anyone have any opinions = or advice=20 to give a rank beginner who has not been in a science classroom or lab = in over=20 40 years?


Regards,

Beno=EEt Evans
Qu=E9bec, = Canada Subject: Re: Comparison of available seismometers From: Brett Nordgren Brett3mr@............. Date: Thu, 31 Jan 2008 11:06:00 -0500 Les, Yes, I do have one question. I may just have missed it, but it wasn't clear to me from the literature, exactly what the frequency response of the VolksMeter was. Is it flat to velocity between two frequencies and what are its sensitivity and corner frequencies? Also how fast does the velocity response fall as you approach zero? If it's easier to express these in terms of displacement or acceleration response, that's fine, too. Poles and zeros would be OK also. Thanks for your help, Brett At 11:01 PM 1/30/2008 -0800, you wrote: >Hello Benoit, > >I am the project engineer for the VolksMeter. I would be happy to answer >any questions you have on the VolksMeter. > >Regards, > >Les LaZar You can always use my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Comparison of available seismometers From: "Les LaZar" llazar@.................. Date: Thu, 31 Jan 2008 13:40:28 -0800 Hi Brett, I believe that the VolksMeter User's Manual, Appendix A - Theory Of Operation, addresses the frequency response issue. The User's Manual is available on-line at our website, www.rllinstruments.com Section 7 (which starts on page 7 of the appendix document) is relevant to your question: http://www.rllinstruments.com/PDF_Files/VM%20II%20UM%20-%20App%201.pdf In short, the frequency response is flat from DC to the natural frequency of the pendulum (~0.9 sec) and then falls off exponentially (linearly on a log scale) at higher frequencies. The practical high frequency limit is 40Hz, which is set by the maximum sampling rate of 80 samples per second (of the electronics). Further, there is a drop off in usable sensor resolution at higher sample rates, so 16 bits is the highest resolution that is usable at 80 sps due to sensor/electronics noise issues. Resolution of 20-24 bits is practical at sample rates in the 20 to 10 sps range (10Hz - 5Hz maximum frequency). For lower frequencies, digital filtering (signal averaging) that is available in the software package can reduce noise still further. The VolksMeter sensor responds to acceleration and/or tilt. Velocity information is derived from the raw data through signal processing (integration in this case) which is part of the included WinSDR/WinQuake software package. I hope this answers your questions. If not, please let me know. Regards, Les LaZar RLL Instruments / a division of Zoltech Corporation ----- Original Message ----- From: "Brett Nordgren" To: Sent: Thursday, January 31, 2008 8:06 AM Subject: Re: Comparison of available seismometers > Les, > > Yes, I do have one question. I may just have missed it, but it wasn't > clear to me from the literature, exactly what the frequency response of > the VolksMeter was. Is it flat to velocity between two frequencies and > what are its sensitivity and corner frequencies? Also how fast does the > velocity response fall as you approach zero? > > If it's easier to express these in terms of displacement or acceleration > response, that's fine, too. Poles and zeros would be OK also. > > Thanks for your help, > > Brett > > At 11:01 PM 1/30/2008 -0800, you wrote: >>Hello Benoit, >> >>I am the project engineer for the VolksMeter. I would be happy to answer >>any questions you have on the VolksMeter. >> >>Regards, >> >>Les LaZar > > > You can always use my mail form at: http://bnordgren.org/contactB.html > using your Web browser. > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of the > message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Comparison of available seismometers From: Brett Nordgren Brett3mr@............. Date: Thu, 31 Jan 2008 18:44:21 -0500 Les, Many thanks. I hadn't looked at the manual, only the spec. page. It sounds like that should have what I'm looking for. Brett At 01:40 PM 1/31/2008 -0800, you wrote: >Hi Brett, > >I believe that the VolksMeter User's Manual, Appendix A - Theory Of >Operation, addresses the frequency response issue. The User's Manual is >available on-line at our website, www.rllinstruments.com Section 7 (which >starts on page 7 of the appendix document) is relevant to your question: >http://www.rllinstruments.com/PDF_Files/VM%20II%20UM%20-%20App%201.pdf > >I hope this answers your questions. If not, please let me know. > >Regards, > >Les LaZar >RLL Instruments / a division of Zoltech Corporation __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Comparison of available seismometers From: "Connie and Jim Lehman" lehmancj@........... Date: Fri, 1 Feb 2008 09:11:38 -0500 Brett--It is always encouraging to see someone gaining an interest in amateur seismology. My suggestion is TO BUILD something for your first system--(there is a half dozen designs out there) and later on you can move to a "black box" that does the work for you. Any seismic system is an electro/mechanical device that you can tune into--understand its workings & improve performance as you go along. There is a satisfaction in a working system where you are part of the nuts & bolts. Best wishes, Jim ----- Original Message ----- From: "Brett Nordgren" To: Sent: Thursday, January 31, 2008 6:44 PM Subject: Re: Comparison of available seismometers > Les, > > Many thanks. I hadn't looked at the manual, only the spec. page. It > sounds like that should have what I'm looking for. > > Brett > > At 01:40 PM 1/31/2008 -0800, you wrote: > >Hi Brett, > > > >I believe that the VolksMeter User's Manual, Appendix A - Theory Of > >Operation, addresses the frequency response issue. The User's Manual is > >available on-line at our website, www.rllinstruments.com Section 7 (which > >starts on page 7 of the appendix document) is relevant to your question: > >http://www.rllinstruments.com/PDF_Files/VM%20II%20UM%20-%20App%201.pdf > > > > > >I hope this answers your questions. If not, please let me know. > > > >Regards, > > > >Les LaZar > >RLL Instruments / a division of Zoltech Corporation > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Design or build? (was Comparison of available seismometers) From: Brett Nordgren Brett3mr@............. Date: Sat, 02 Feb 2008 10:06:09 -0500 Jim, Your suggestion is greatly appreciated. It is perhaps a whole lot more appropriate than you might first have thought, and I hope that I may be forgiven if I use List bandwidth for some random babbling. I have struggled for years deciding whether I wanted to spend my available time working on designing and analyzing (I had done my first primitive feedback seismo. design back in the 60's) or whether I wanted to really build something and become a 'wiggle watcher'. Before my neighbor, Bob Barns, died last spring, I satisfied the latter need by working with his setup. Now I'm facing the question of whether to start diverting time from analysis and design (always more to be done) to construction. With the enormous amount of data available online, watching wiggles does sometimes seem like reinventing the wheel, however, creating and running a station would be an excellent experience for our grandkids who live nearby, and that's now tipping my thinking in favor of taking your suggestion to start building something. As a retired instrument designer, I tend to fall into the old pattern. You spent as much time as was available designing and analyzing on paper. Then you turned your design over to someone to build a prototype. When the protype was done, you tested it, and if your design and analysis had been done well it would work pretty much as expected and could promptly be sent on to Production. Though it's many years since I was doing that, I still find that the creating of good designs is very satisfying to me. And then, I enjoy trying to put the results of my work into a form that can be shared, hopefully to help out folks who are wanting to build and understand their own feedback instruments. Guess I'd better get to work before the grandkids grow up and are out of here. Best regards, Brett At 09:11 AM 2/1/2008 -0500, you wrote: >Brett--It is always encouraging to see someone gaining an interest in >amateur seismology. My suggestion is TO BUILD something for your first >system--(there is a half dozen designs out there) and later on you can move >to a "black box" that does the work for you. Any seismic system is an >electro/mechanical device that you can tune into--understand its workings & >improve performance as you go along. There is a satisfaction in a working >system where you are part of the nuts & bolts. > Best wishes, Jim __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Comparison of available seismometers From: Brett Nordgren Brett3mr@............. Date: Sat, 02 Feb 2008 12:23:01 -0500 Benoit, I think I may have replied to a message from Jim Lehman that he had meant=20 for you. However, I can offer a couple of comments on your question. The first=20 three designs are verticals, more like the LaCoste design than the=20 Lehman. It's not clear what their sensitivity and frequency responses are,= =20 but they look like they would be flat to velocity over a moderate frequency= =20 range. How wide a range would depend on how much damping they are getting= =20 with their oil dampers. The Volksmeter is a horizontal device, narrow-band to velocity centered at= =20 1Hz and with an acceleration response flat from DC to 1Hz. Whether a vertical or horizontal device is 'better' can be debated, but=20 they each have their own advantages and disadvantages. Brett At 09:52 PM 1/30/2008 -0500, you wrote: >I am interested in acquiring a simple seismometer package for amateur use= =20 >that is sensitive enough to detect teleseismic events. I would like to=20 >acquire a ready-to-use instrument rather than build something from scratch= =20 >or from a kit. My main question is which seismometer to buy. I have come=20 >across the following instruments on the Web: > >AS-1 Amateur Seismologist (Jeff Batten) $550 ??? >http://www.amateurseismologist.com > >Vertical School Seismometer Ward=92s Natural Science $500 >h= ttp://www.wardsci.com/Product.asp_Q_cmss_E_seismometer_A_pn_E_IG0018602=20 > > >EQ-1 Next Generation Science $600 >http://www.nex= gensci.com/store/pc/viewPrd.asp?idproduct=3D1=20 > > >Volksmeter II RLL Instruments (Zoltech) $995 single channel, $1495=20 >dual channel >(patented Symmetric Differential Capacitor (SDC) array sensor) >http://www.rllinstruments.com > >In spite of the price difference, the Volksmeter seems interesting. As far= =20 >as I an tell, it is based on recent technology that is different form the= =20 >other three, which seem to be of the traditional Lehman type. > >Does anyone have any opinions or advice to give a rank beginner who has=20 >not been in a science classroom or lab in over 40 years? > > >Regards, > >Beno=EEt Evans >Qu=E9bec, Canada > > > > > My e-mail address above should be working, but if not >you can always use my mail form at: http://bnordgren.org/contactB.html > using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Digest from 02/02/2008 00:00:01 From: Randall Peters PETERS_RD@.......... Date: Sun, 03 Feb 2008 10:49:46 -0500 Brett, When you refer to the VolksMeter's response being flat from D.C. to 1 Hz, you are correct; however, to say that the velocity response is narrow-band is not. The difference between acceleration response (position sensor such as the VolksMeter0 and velocity response (most seismometers) is summed up by the upper right pair of graphs shown on John Lahr's page at http://jclahr.com/science/psn/response/plots.jpg These illustrate (for perfect electronics if it existed) the difference between an 'acceleration' detector (VolksMeter) and a 'jerk' detector (conventional instruments that use a Faraday-law--magnet coil- detector) in terms of their response to earth's motion. The only thing that causes any seismometer to respond is acceleration (or tilt as a special case therof), and so the conventional instrument is measuring the derivative of the acceleration, which engineers call the 'jerk'. For 'perfect' electronics, the acceleration response is superior for sensing lower frequencies of earth motion, whereas the jerk response is superior for higer frequencies. The limit of detectability, within the differing constraints of their architecture, is the noise introduced by the electronics. My statement about 'superiority' assumes equally effective electronics for the cases. Randall Subject: Re: Digest from 02/02/2008 00:00:01 From: Brett Nordgren Brett3mr@............. Date: Sun, 03 Feb 2008 13:20:48 -0500 Randall, I think I might have done better if I had made it clearer that the instrument response is distinct from the transducer response. I completely agree that to create the highest performance instrument you have to use a good displacement transducer, as the VolksMeter does. At 10:49 AM 2/3/2008 -0500, you wrote: >Brett, > When you refer to the VolksMeter's response being flat from D.C. to > 1 Hz, you >are correct; however, to say that the velocity response is narrow-band is not. >The difference between acceleration response (position sensor such as the >VolksMeter0 and velocity response (most seismometers) is summed up by the >upper >right pair of graphs shown on John Lahr's page at >http://jclahr.com/science/psn/response/plots.jpg However, the overall instrument response to sinusoidal ground motion described by displacement, shown as the blue line in figure P2 of the User's Manual, rises from DC at 40db per decade, and levels out at unity at about 0.9Hz. That implies that the instrument response, if the ground motion were instead described by its velocity, would rise from DC at 20db per decade to a maximum at 0.9Hz at which point it begins to fall at 20db per decade. I had understood that in commercial instruments, that was usually described as a narrow-band velocity response. I would contend that the same instrument can be characterized by stating either its response to displacement (flat above 0.9Hz) or to velocity (peaking at 0.9Hz), or for that matter to ground acceleration (flat below 0.9Hz). Different curves, same device. > These illustrate (for perfect electronics if it existed) the difference >between an 'acceleration' detector (VolksMeter) and a 'jerk' detector >(conventional instruments that use a Faraday-law--magnet coil- detector) >in terms >of their response to earth's motion. The only thing that causes any >seismometer >to respond is acceleration (or tilt as a special case therof), and so the >conventional instrument is measuring the derivative of the acceleration, which >engineers call the 'jerk'. Yes. I was first introduced to the technical use of the term when I was 15 by my engineer father. It was, as I recall, in connection with my early attempts at driving. > For 'perfect' electronics, the acceleration response is superior for > sensing >lower frequencies of earth motion, whereas the jerk response is superior >for higer >frequencies. The limit of detectability, within the differing constraints of >their architecture, is the noise introduced by the electronics. My statement >about 'superiority' assumes equally effective electronics for the cases. > Randall Brett My e-mail address above should be working, but if not you can always use my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Volksmeter (was Digest...) From: Brett Nordgren Brett3mr@............. Date: Mon, 04 Feb 2008 14:18:41 -0500 Randall, In order to clear my thinking, I put together an Excel spreadsheet which describes an experiment with the VolksMeter in which it is placed on a horizontal shaker table, oscillating with constant amplitude of 0.01mm, swept over a frequency range of 0.002Hz to 10Hz. The pendulum parameters and sensitivity numbers were obtained from the VM User Manual and its response was plotted in several ways. The zipped file is at http://bnordgren.org/seismo/VolksMeter.zip (Note that upper/lower case counts on my server). This unzips to 'VolksMeter.xls' which has a worksheet with the calculations and three charts to display the results. Please let me know if/where I may have gotten my sums wrong, Many thanks, Brett Nordgren At 10:49 AM 2/3/2008 -0500, you wrote: >Brett, > When you refer to the VolksMeter's response being flat from D.C. to > 1 Hz, you >are correct; however, to say that the velocity response is narrow-band is not. >The difference between acceleration response (position sensor such as the >VolksMeter0 and velocity response (most seismometers) is summed up by the >upper >right pair of graphs shown on John Lahr's page at >http://jclahr.com/science/psn/response/plots.jpg > These illustrate (for perfect electronics if it existed) the difference >between an 'acceleration' detector (VolksMeter) and a 'jerk' detector >(conventional instruments that use a Faraday-law--magnet coil- detector) >in terms >of their response to earth's motion. The only thing that causes any >seismometer >to respond is acceleration (or tilt as a special case therof), and so the >conventional instrument is measuring the derivative of the acceleration, which >engineers call the 'jerk'. > For 'perfect' electronics, the acceleration response is superior for > sensing >lower frequencies of earth motion, whereas the jerk response is superior >for higer >frequencies. The limit of detectability, within the differing constraints of >their architecture, is the noise introduced by the electronics. My statement >about 'superiority' assumes equally effective electronics for the cases. > Randall My e-mail address above should be working, but if not you can always use my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: transfer functions From: Randall Peters PETERS_RD@.......... Date: Mon, 04 Feb 2008 17:37:12 -0500 Brett, I see nothing wrong with the Excel sheets that you've generated--at least in terms of the relative shapes of the transfer functions expressed in terms of either (i) ground acceleration, or (ii) velocity, or (iii) displacement (the system state variables). It is critically important to understand, however, that these three transfer curves are not all equally important. Acceleration is what results in velocity, which in turn results in displacement. The only way to treat the dynamics is by means of Newton's 2nd law, which is in terms of acceleration. Moreover, the only state variable responsible for moving the inertial mass relative to the case of a seismometer is ACCELERATION. Even in the case of tilt, the response is due to acceleration. In this special case of tilt, it is the case moving relative to the essentially stationary pendulum that gives rise to a response. And the amount of response is determined by the component of the earth's field (little g = 9.8 m/s^2) that is perpendicular to the pendulum. Where the tilt is different from the usual acceleration response is that it has no frequency response associated with it. Now about your analysis approach (which is conventional): it is a steady state analysis, assuming harmonic excitation. The only excitation mechanism is (as I've tried to emphatically point out) -- ground acceleration. The velocity is obtained from this acceleration by means of integration, and in turn the displacement is obtained by integrating the velocity. ONLY if the harmonic excitation persists for a long enough interval of time to be reasonably monochromatic--is it possible to obtain an approximation for the aforementioned integrals by simply dividing a given expression by the angular frequency. I can give you a good example of where this does not work. With the VolksMeter I routinely see near-discontinuous displacements (due to tilt). Sometimes they are a step and sometimes they are a pulse (bistability). They generally happen at levels close to that of the noise (whether ground or electronic). If one takes the derivative of such a signal (what one would see with the conventional detectors), they are almost never observable--even though they are clearly visible in the raw data. This is for two reasons: (i) the derivative only yields two spikes that look much like noise, and (ii) the derivative is fundamentally a 'noise-producing' operation. What has confused so many people derives from the nature of the detectors employed. For example, the Faraday law detector (magnet/coil) that has been used for many years, does not really measure the velocity of the ground. The output that it generates is proportional to the velocity of the inertial mass relative to the case of the seismometer. Since the mass movement is proportional to the acceleration of the earth, the common detector is thus really responding to the derivative of ground acceleration (the jerk). If one wants to really see an output that is a proper representation of ground velocity, then take a look at the VolksMeter's integrated signal. The world is hung up on steady state, linear system analysis--not recognizing that it has limitations. One can't simply operate with a convenient but aritificial transfer function (such as 'velocity' or 'displacment') and get the right answer all the time by means of the simple transformations involving the angular frequency. The proper treatment iinvolves actually doing the integrals! Even the pole/zero description that is routinely mentioned is one that at its foundation embraces the transient consequences of changes that are too short-lived for the steady state assumptions to be valid. Just because the instrument is near-critically damped does not mean that there are no transient features! Randall Subject: more on transfer functions From: Randall Peters PETERS_RD@.......... Date: Wed, 06 Feb 2008 16:11:33 -0500 Brett, Probably the most important thing about the differences among the transfer functions for the different state variables is their differing functional dependence of SNR. The multiplication by angular frequency, when working with the derivative ('velocity sensor')--causes the power spectral density in that case to approach the electronics noise level more rapidly at low frequencies than is true for the position sensor case. In other words the signal goes below noise more rapidly for the velocity sensor than for the position sensor, as the frequency decreases. A sensor that is 'flat to velocity' is not immune to this limitation; since acceleration, being fundamental (and not velocity) is what regulates the frequency dependence of the signal to noise ratio. A way to understand the importance of the electronic noise in this matter is as follows. Nobody should question the fact that the only thing that allows any sensor to function is the transfer of power to it. In the case of a seismometer, the specific power (power divided by the magnitude of the inertial mass) is given by the product of velocity and acceleration. Students of physics should remember the expression for mechanical power as the dot product of force and velocity. In terms of acceleration, the specific power is given by the square of the peak acceleration divided by the angular frequency--having units of meters squared per second cubed. When the spectral density of the power is graphed Log-Log (or dB-Log), the logarithmic linear 'compression' in frequency of the FFT values (which are equispaced for a linear scale) causes the reciprocal omega term to disappear. In other words, for a position sensor, the mechanical specific power, in a spectral density sense, is constant for frequencies below the corner frequency. Those familiar with Jon Berger's well known paper on earth noise will remember that the ordinate of his power spectral density (PSD) graphs is specified in terms of meters squared per second cubed per one-seventh decade (expressed in dB). (Note: his graphs do not specifically mention the bin-width of one-seventh decade; this must be understood from written descriptions in the paper.) His units are consistent with what I have just indicated, but the common (erroneous) meters squared per second to the fourth per Hz are not! In fact, these common units cannot be a proper power spectral density statement, because they are dimensionally unacceptable. Whereas the PSD is flat below the corner when calculated with data from a position sensor, the same is not true in the case of a velocity sensor. In the velocity case, the power is given by omega times the square of the peak value of the velocity. The PSD is in turn (because of the compression mentioned in the usual Log-Log representation) given by omega squared times the square of the peak velocity. Thus, as omega (two pi times the frequency) decreases below the corner value, the PSD expression decreases with the square of the frequency--falling off 20 dB per decade. Just from the electronics noise alone, we see that with the velocity sensor--as frequency decreases--a point is reached where the mechanical PSD falls below the power spectral density of electronics noise. Thereafter, unless some noise reduction scheme is employed the signal responsible for mechanical motion below those frequencies--cannot be seen with the velocity sensor. They can, however, still be seen with the position sensor. Randall Subject: Re: more on transfer functions From: Brett Nordgren Brett3mr@............. Date: Thu, 07 Feb 2008 21:31:41 -0500 Randall, Thanks for the excellent discussion. You answered a number of questions that had been bugging me regarding PSD. And I would also highly recomment your VolksMeter manual http://rllinstruments.com/UM_index.htm Appendix I, for a more extensive discussion of noise. Just for the record, I have always believed that you could get better performance by using a position transducer as the detector. The main justification for velocity sensing is that it is likely to be quite a bit easier to implement, and if your goal is to successfully view earthquakes, a velocity sensor can do a fine job. However when you start wanting to push the envelope in terms of sensitivity, frequency span, etc. I agree with your point that you are going to have to start seriously considering position sensing. There is a related issue, concerning the use of feedback to shape the instrument response. If the signal to noise you are describing is ground motion signal to instrument noise, one of the precepts of feedback theory is that feedback can never improve or degrade signal to noise ratio. Any time you reduce a signal in a particular frequency band by means of feedback, you also reduce the instrument noise in that band in the identical proportion. Similarly you can not improve signal to noise by using feedback. Only in the case where the signal and noise energy are predominately in different frequency bands, can you can make use of feedback to, in some degree, reject one and enhance the other. (which can sometimes be quite useful) I realize that doesn't particularly relate to your point, but it's useful to bear in mind when considering feedback designs. Brett At 04:11 PM 2/6/2008 -0500, you wrote: >Brett, > Probably the most important thing about the differences among the > transfer >functions for the different state variables is their differing >functional dependence of SNR. The multiplication by angular frequency, when >working >with the derivative ('velocity sensor')--causes >the power spectral density in that case to approach the electronics noise >level >more >rapidly at low frequencies than is true for the >position sensor case. In other words the signal goes below noise more >rapidly for >the >velocity sensor than for the position sensor, as >the frequency decreases. A sensor that is 'flat to velocity' is not immune to >this >limitation; since acceleration, being fundamental (and not velocity) is what >regulates >the frequency dependence of the signal to noise ratio. > A way to understand the importance of the electronic noise in this > matter is >as >follows. Nobody should question the fact >that the only thing that allows any sensor to function is the transfer of >power to > >it. In the case of a seismometer, the specific power >(power divided by the magnitude of the inertial mass) is given by the >product of >velocity and acceleration. Students of physics should >remember the expression for mechanical power as the dot product of force and >velocity. In terms of acceleration, the specific power is given by the >square of >the >peak acceleration divided by the angular frequency--having units of meters >squared >per >second cubed. When the spectral density of the power is graphed Log-Log (or >dB-Log), >the logarithmic linear 'compression' in frequency of the FFT values (which are >equispaced for a linear scale) causes the reciprocal omega term to >disappear. In >other words, for a position sensor, the mechanical specific power, in a >spectral >density sense, is constant for frequencies below the corner frequency. Those >familiar >with Jon Berger's well known paper on earth noise will remember that the >ordinate >of >his power spectral density (PSD) graphs is specified in terms of meters >squared >per >second cubed per one-seventh decade (expressed in dB). (Note: his graphs >do not >specifically mention the bin-width of one-seventh decade; this must be >understood >from >written descriptions in the paper.) His units are consistent with what I have >just >indicated, but the common (erroneous) meters squared per second to the >fourth per >Hz >are not! In fact, these common units cannot be a proper power spectral >density >statement, because they are dimensionally unacceptable. > Whereas the PSD is flat below the corner when calculated with data > from a >position sensor, the same is not true in the case of a velocity >sensor. In the >velocity case, the power is given by omega times the square of the peak >value of >the >velocity. The PSD is in turn (because of the compression mentioned in the >usual >Log-Log representation) given by omega squared times the square of the peak >velocity. >Thus, as omega (two pi times the frequency) decreases below the corner >value, the >PSD >expression decreases with the square of the frequency--falling off 20 dB per >decade. > Just from the electronics noise alone, we see that with the velocity >sensor--as >frequency decreases--a point is reached where the mechanical PSD falls >below the >power >spectral density of electronics noise. Thereafter, unless some noise >reduction >scheme >is employed the signal responsible for mechanical motion below those >frequencies--cannot be seen with the velocity sensor. They can, however, >still be > >seen with the position sensor. > >Randall > > > you can always use my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Digest from 02/07/2008 00:00:25 From: Randall Peters PETERS_RD@.......... Date: Fri, 08 Feb 2008 08:55:25 -0500 Thanks, Brett. Clearly you're both willing and able to look at the physics facts involving seismometers. What's appalling to me is how much false information exists on the matter. Considering the widespread deployment and importance of seismometers, one would naturally believe that the performance issues would have been properly treated by theory many years ago. Fact is, they have not been, insofar as I can tell. The power spectral density is the means to understand not just performance, but also what's happening in the earth--whether earthquakes or whatever. (Actually, the cumulative spectral power, obtained from the PSD--permits us to more easily observe the evolutionary changes.) Other than myself, equipment manufacturers seem to be the only ones who ever look at the PSD; and they limit their plots to benchmarking (to tout their wares)--and what gets graphed is dimensionally incorrect, even though they've got the right numbers on their plots (by accident, it appears). On this matter I have been trying for some time now to bring long overdue corrections to the professional seismology community. They remain `quiet' and seemingly unwilling to debate the issues. I've tried to follow the path of diplomacy, but it seems to have failed. Consequently, my next choice has been to 'speak to the issues plainly'; which is not without controversy. In the famous words of the astronomer Fritz Zwicki, there is a resulting tendency for antagonists to view one another as 'spherical bastards' ".... bastards, when looked at from any side". On 'everything2.com' we find the comment: Zwicky was well-known for his colorful metaphors, but what makes people the angriest is that, regarding the existence of dark matter, he seems to have been right. We in physics (not just astronomy) strive diligently to discover 'what is right'; and I believe that what I've been telling people is correct. It is alien to my profession to try and 'kill with silence'. Issues get debated--sometimes with the appearance that a 'knock-down drag out fight' is about to happen. But after the 'truth' has been hammered out, such combatants have not in my experience become great enemies; they are not given to either (i) gloating over success, nor (ii) simmering in a 'pitty-party' for having been wrong. I must admit that I don't understand how the geoscience profession appears from my perspective to be so different. About your statement concerning feedback. It's been the better part of a decade that I've been trying to tell folks that feedback (of the force balance type) is not the 'cure-all' that everybody wants to believe. Its most important deficiencies derive from the fact that mother nature is never linear. Thank God that many of our linear approximations are at times quite adequate. But in the case of force-balance at low frequencies, my position has been (and remains) the following. Internal friction of the seismometer structure 'wars against' the very premise around which the instruments are designed. The system is characterized, not by a harmonic potential (basis for linear theory) but rather by 'fine structure' in the potential well. These exist at the mesoscale--place where I've been doing research for nearly two decades. This fine structure is a form of nonlinearity that is much more important to seismometer performance (at low frequencies and low levels) than the nonlinearity that seismometer designers talk about; i.e., at large amplitude. Nature has two forms of anharmonicity--`elastic' that is important at large levels with springs that don't `work right', and `damping' (due to deffect structures) at low levels. If my article dealing with these forms of anharmonicity, published in the 10th Ed. of the McGraw Hill Encyclopedia of Science and Technology should be a valid indicator; then I'm the only person to have researched the 'damping' type that regulates seismometer performance. As an engineer you will appreciate something that is needed for the improvement of force balance instruments. Friction-limited systems have to be dithered to overcome the adversities of the friction. In the modern terminology of physics, we describe this in terms of 'stochastic resonance'. Fact is, nobody understands friction from 'first principles'. All we know derives from empericism. The level of our universal ignorance needs to decrease, if we are to make really small seismometers work well (which they do not). I maintain that the SNR limitations of MEMS-type instruments derives from the mesoanelastic complexity (internal friction) that is not understood. Among other things, I believe this complexity is responsible for a totally worthless calculation that is routinely used by professional seismologists; i.e., calculate the Brownian motion of the seismic mass as though the mechanical noise could be assumed to derive from a system with only two square terms iin the Hamiltonian (equipartition theorem, associated wtih fluctuation-dissipation). Randall psn-l-digest-request@.............. wrote: > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 1 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: more on transfer functions > From: Brett Nordgren > Date: Thu, 07 Feb 2008 21:31:41 -0500 > > Randall, > > Thanks for the excellent discussion. You answered a number of questions > that had been bugging me regarding PSD. And I would also highly recomment > your VolksMeter manual http://rllinstruments.com/UM_index.htm Appendix > I, for a more extensive discussion of noise. > > Just for the record, I have always believed that you could get better > performance by using a position transducer as the detector. The main > justification for velocity sensing is that it is likely to be quite a bit > easier to implement, and if your goal is to successfully view earthquakes, > a velocity sensor can do a fine job. However when you start wanting to > push the envelope in terms of sensitivity, frequency span, etc. I agree > with your point that you are going to have to start seriously considering > position sensing. > > There is a related issue, concerning the use of feedback to shape the > instrument response. If the signal to noise you are describing is ground > motion signal to instrument noise, one of the precepts of feedback theory > is that feedback can never improve or degrade signal to noise ratio. Any > time you reduce a signal in a particular frequency band by means of > feedback, you also reduce the instrument noise in that band in the > identical proportion. Similarly you can not improve signal to noise by > using feedback. Only in the case where the signal and noise energy are > predominately in different frequency bands, can you can make use of > feedback to, in some degree, reject one and enhance the other. (which can > sometimes be quite useful) > > I realize that doesn't particularly relate to your point, but it's useful > to bear in mind when considering feedback designs. > > Brett > > At 04:11 PM 2/6/2008 -0500, you wrote: > >Brett, > > Probably the most important thing about the differences among the > > transfer > >functions for the different state variables is their differing > >functional dependence of SNR. The multiplication by angular frequency, when > >working > >with the derivative ('velocity sensor')--causes > >the power spectral density in that case to approach the electronics noise > >level > >more > >rapidly at low frequencies than is true for the > >position sensor case. In other words the signal goes below noise more > >rapidly for > >the > >velocity sensor than for the position sensor, as > >the frequency decreases. A sensor that is 'flat to velocity' is not immune to > >this > >limitation; since acceleration, being fundamental (and not velocity) is what > >regulates > >the frequency dependence of the signal to noise ratio. > > A way to understand the importance of the electronic noise in this > > matter is > >as > >follows. Nobody should question the fact > >that the only thing that allows any sensor to function is the transfer of > >power to > > > >it. In the case of a seismometer, the specific power > >(power divided by the magnitude of the inertial mass) is given by the > >product of > >velocity and acceleration. Students of physics should > >remember the expression for mechanical power as the dot product of force and > >velocity. In terms of acceleration, the specific power is given by the > >square of > >the > >peak acceleration divided by the angular frequency--having units of meters > >squared > >per > >second cubed. When the spectral density of the power is graphed Log-Log (or > >dB-Log), > >the logarithmic linear 'compression' in frequency of the FFT values (which are > >equispaced for a linear scale) causes the reciprocal omega term to > >disappear. In > >other words, for a position sensor, the mechanical specific power, in a > >spectral > >density sense, is constant for frequencies below the corner frequency. Those > >familiar > >with Jon Berger's well known paper on earth noise will remember that the > >ordinate > >of > >his power spectral density (PSD) graphs is specified in terms of meters > >squared > >per > >second cubed per one-seventh decade (expressed in dB). (Note: his graphs > >do not > >specifically mention the bin-width of one-seventh decade; this must be > >understood > >from > >written descriptions in the paper.) His units are consistent with what I have > >just > >indicated, but the common (erroneous) meters squared per second to the > >fourth per > >Hz > >are not! In fact, these common units cannot be a proper power spectral > >density > >statement, because they are dimensionally unacceptable. > > Whereas the PSD is flat below the corner when calculated with data > > from a > >position sensor, the same is not true in the case of a velocity > >sensor. In the > >velocity case, the power is given by omega times the square of the peak > >value of > >the > >velocity. The PSD is in turn (because of the compression mentioned in the > >usual > >Log-Log representation) given by omega squared times the square of the peak > >velocity. > >Thus, as omega (two pi times the frequency) decreases below the corner > >value, the > >PSD > >expression decreases with the square of the frequency--falling off 20 dB per > >decade. > > Just from the electronics noise alone, we see that with the velocity > >sensor--as > >frequency decreases--a point is reached where the mechanical PSD falls > >below the > >power > >spectral density of electronics noise. Thereafter, unless some noise > >reduction > >scheme > >is employed the signal responsible for mechanical motion below those > >frequencies--cannot be seen with the velocity sensor. They can, however, > >still be > > > >seen with the position sensor. > > > >Randall > > > > > > > > you can always use my mail form at: http://bnordgren.org/contactB.html > using your Web browser. > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-DIGEST-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. Subject: Re: Hekla volcano geophone planned From: ian ian@........... Date: Fri, 08 Feb 2008 14:23:47 +0000 Hi, today's mid-Atlantic quake saturated my high gain channel (+/-0.1V), so a lot of the data comes from the mid-gain channel (+/-1.0V) The trace is a bit noisy with the strong winds here causing the trees to bend and twist. Cheers Ian http://www.iasmith.com ChrisAtUpw@....... wrote: > In a message dated 06/01/2008, ian@........... writes: > > Looking back I can see that there are a few traces (not many) which > flipped between channel gains +/-0.1V and +/-1.0V. So the feature is > giving me more gain to look into the weaker signals without being > clobbered with saturation on the stronger traces - both the high > and low > pass filters apply a 20db gain to compensate for the attenuation > of the > filters. > > Hi Ian, > > I would expect that all your out of range signals will be due to > the surface waves? > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: More on transfer functions From: Brett Nordgren Brett3mr@............. Date: Fri, 08 Feb 2008 12:11:09 -0500 Randall, Since you and I both seem to think in terms of paragraphs and chapters rather than sentences, I'll take the liberty of only quoting the things that I am replying to, so that folks' in-boxes don't get overloaded. Hope that's OK. At 08:55 AM 2/8/2008 -0500, you wrote: >Thanks, Brett. > About your statement concerning feedback. It's been the better part of a >decade that I've been trying to tell folks that feedback (of the force balance >type) is not the 'cure-all' that everybody wants to believe. I have a paper in the works that is directed at some aspects of that issue, but I need to fix up a few errors, before I let it out. I believe that feedback can accomplish a lot (perhaps more than you do), but there are many things that it doesn't do, and that's one thing I was planning to illustrate. >Its most important >deficiencies derive from the fact that mother nature is never >linear. Thank God >that many of our linear approximations are at times quite adequate. But >in the >case of force-balance at low frequencies, my position has been (and >remains) the >following. Internal friction of the seismometer structure 'wars against' >the very >premise around which the instruments are designed. The system is >characterized, >not by a harmonic potential (basis for linear theory) but rather by 'fine >structure' in the potential well. In particular, would it be sufficient to treat these issues by defining the without-feedback device as if it had a damping coefficient which is nonlinear to velocity and perhaps even time-varying? i.e. can you write the equations in a quasi-linear form, simply identifying the terms which don't behave? Then you might be able to apply the usual linear feedback equations and hopefully (for me) demonstrate that the 'bad' terms become insignificant in the result. Or is there some better approach which can allow us to properly incorporate the effects which you describe into an analysis of the actual device characteristics we would obtain with feedback, for instruments of the size of interest to this group? I'm uncomfortable with taking the approach that because there exist some fairly small (I think) nonlinear effects, then no quantitative analysis can be valid at all. Although it's somewhat beyond my experience, I believe that feedback designers today routinely deal with highly nonlinear, time-varying, and stochastic system variables and still are able to obtain quite useful results. If they couldn't there would be a lot fewer airplanes out there and our cars wouldn't handle as well. Brett >These exist at the mesoscale--place where I've >been doing research for nearly two decades. This fine structure is a form of >nonlinearity that is much more important to seismometer performance (at low >frequencies and low levels) than the nonlinearity that seismometer >designers talk >about; i.e., at large amplitude. Nature has two forms of >anharmonicity--`elastic' >that is important at large levels with springs that don't `work right', and >`damping' (due to deffect structures) at low levels. If my article >dealing with >these forms of anharmonicity, published in the 10th Ed. of the McGraw Hill >Encyclopedia of Science and Technology should be a valid indicator; then >I'm the >only person to have researched the 'damping' type that regulates seismometer >performance. > Randall __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: fine structure nonlinearity vs dithering From: "Charles R. Patton" charles.r.patton@........ Date: Fri, 08 Feb 2008 11:50:54 -0800 Randall, One brief thought -- I''m familiar with dithering to solve frictional problems. So why not dither the force feedback at the A/D sample rate? The friction non-linearity would generate harmonics of the dither frequency, but these would also be rejected by the synchronous sampling of the A/D (they would show up as a DC offset -- i.e., it would appear as if the seismometer had a tilt that was not there in reality.) The question is, "Does the "fine structure nonlinearity" show up as random stiction/rachetting?" I.e., if one was to dither the force feedback, would the result be a lifting of the noise spectrum floor and result in overwhelming broadband noise? As an aside, Brett asked you to start a direct email of this discussion off the PSN list. I would hope this doesn't happen. I can't learn from a discussion I don't have contact with. :-) Regards, Charles R. Patton Randall Peters wrote: > As an engineer you will appreciate something that is needed for the improvement > of force balance instruments. Friction-limited systems have to be dithered to > overcome the adversities of the friction. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: dithering From: Randall Peters PETERS_RD@.......... Date: Fri, 08 Feb 2008 17:00:28 -0500 Charles, I had started to correspond with Brett as he indicated. Copied below is what I sent to him. About your question--I would need to give some serious thought to your idea before commenting. As engineers, you and Brett probably have more experience with some of these issues than myself. At any rate, as noted below--I don't think dithering of force-balance velocity sensing instruments is the way to go. What is needed at low frequencies is a whole different approach that I mention. Incidently, I have proven its viability (soft-feedback with a long time constant integrator) with my modified Sprengnether (LaCoste vertical). Randall Brett, I'm not saying that the feedback systems are not good. The STS-1 ( 'crown jewel') is a marvel of technology when it comes to earthquake detection most anywhere. What I am trying to communicate is the very thing you alluded to in one of your points--as frequency goes toward zero (where the community wants to operate for studying 'earth hum'), the ability to see important motions with a velocity sensor also goes toward zero. The sad part is that the seismo-pro's don't seem to undertand how this can be so. I am not at all opposed to feedback; what I'm opposed to is the insistence that the only way to do it is by forcing the system into a 'flat-to-velocity' response by means of force balance. For a long time now I've been advocating what is the obvious solution to the low frequency conundrum; i.e., a soft-force feedback (not force balance) that keeps the system from 'going to the rails' as the period is lengthened to give the kind of mechanical sensitivity that is needed for good teleseismic response using a displacement sensor. Without feedback in the case of a vertical seismometer, the sensitivity can never be great enough to yield outstanding performance--because of the effects of (i) buoyancy change due to atmospheric pressure variations, and (ii) spring constant change with temperature because of the thermal coefficient of the modulus. Without some type of compensation, the latter is a killer when one tries to obtain a natural period of 20 s. I didn't intend to suggest that force balance is not a great technological achievement (since clearly it is). It is not, however, the cure-all for every sensing regime that many folks seem to believe. About state of the art--one has to be careful what is meant by the term. There are those who believe we must somehow continue with force-balance improvement in order to study the long-period features of the earth. This is not the case, and I think that force balance has gone as far as it can toward low frequencies. The VolksMeter, at about one-tenth of the price of the force balance instruments will outperform the very best of them when it comes to measurements with periods longer than a few thousand seconds. On the other hand, as compared to their telesismic sensitivity, the VolksMeter is severely limited. Bottom line--there is not (and probably never will be) a single instrument that can cover the whole spectrum of interest to seismologists. Randall Subject: Re: fine structure nonlinearity vs dithering From: Brett Nordgren Brett3mr@............. Date: Fri, 08 Feb 2008 19:16:47 -0500 Charles, I'm very glad to hear that you're interested in following the discussion. My only concern had been that we were taking up bandwidth on stuff that might not have been of interest to all that many folks. I'll happilly continue posting my comments, though will also be happy to take this elsewhere if there's a sense that we should. In reply to your comments, I don't yet understand how the nonlinearity acts and how it should mathematically be treated. In a flat to velocity design, if it acts at all like regular linear spring-mass damping, it would be completely overwhelmed by the feedback. The amount of linear velocity damping of a spring-mass has virtually no effect on the response of a flat-to velocity feedback instrument. The way spring-mass damping acts in feedback designs with other responses (flat to acceleration?) might well be different. Regards, Brett FYI, below is what I'd written to Randall, He may want to post his reply. >Randall, > >I assume that you don't believe that feedback is worthless in the >implemtation of seismic sensors, but you obviously feel that there are >some deficiencies in the presently available feedback instruments. The >first question that comes to mind, is what effects would you expect to see >in the performance of those instruments which would relate to the effects >you describe? Can one come up with some experimental design to highlight >the areas in which they fall short? > >I'm reluctant at this point to throw the baby out with the bath water and >accept that linear analysis is of no value in feedback seismometer design, >but I am quite willing to accept that there are areas that have not been >adequately explored in both theory and experiment. For one thing, I need >to understand to what degree you feel the anomalous behavior you describe >extends to designs which aren't attempting to push the state of the >art. Just when would these effects begin to be felt as you tried to >extend performance? > >Regards, >Brett At 11:50 AM 2/8/2008 -0800, you wrote: >Randall, >One brief thought -- I''m familiar with dithering to solve frictional >problems. So why not dither the force feedback at the A/D sample rate? >The friction non-linearity would generate harmonics of the dither >frequency, but these would also be rejected by the synchronous sampling of >the A/D (they would show up as a DC offset -- i.e., it would appear as if >the seismometer had a tilt that was not there in reality.) The question >is, "Does the "fine structure nonlinearity" show up as random >stiction/rachetting?" I.e., if one was to dither the force feedback, >would the result be a lifting of the noise spectrum floor and result in >overwhelming broadband noise? > >As an aside, Brett asked you to start a direct email of this discussion >off the PSN list. I would hope this doesn't happen. I can't learn from a >discussion I don't have contact with. :-) >Regards, >Charles R. Patton __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: fine structure nonlinearity vs dithering From: ChrisAtUpw@....... Date: Fri, 8 Feb 2008 23:29:24 EST In a message dated 09/02/2008, Brett3mr@............. writes: Charles, I'm very glad to hear that you're interested in following the discussion. My only concern had been that we were taking up bandwidth on stuff that might not have been of interest to all that many folks. In reply to your comments, I don't yet understand how the nonlinearity acts and how it should mathematically be treated. Hi Brett, I would be quite happy to 'go public' if no one else objects? I'm uncomfortable with taking the approach that because there exist some fairly small (I think) nonlinear effects, then no quantitative analysis can be valid at all. Although it's somewhat beyond my experience, I believe that feedback designers today routinely deal with highly nonlinear, time-varying, and stochastic system variables and still are able to obtain quite useful results. If they couldn't there would be a lot fewer airplanes out there and our cars wouldn't handle as well. Read through the papers on Randall's Website? Your car analogy misses the point. We are concerned mostly with microscopic as opposed to macroscopic variations. The mechanical properties of springs have a 'fine structure' of discontinuous steps, a bit like ferro magnetic domains. This gives small 'step function' variations and limits the ultimate performance of seismometers, clocks, MEMS devices, etc. The macroscopic properties are also not quiite linear and are time dependant. Hooke's Law is only an approximation. How would you suggest incorporating step functions which are random in time, sense and amplitude into the calculations / properties of a feedback loop? The stochastic processes you mentioned? Regards, Chris Chapman
In a message dated 09/02/2008, Brett3mr@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Charles,
I'm very glad to hear that you're interested in follo= wing=20 the discussion.  My only concern had been that we were taking up=20 bandwidth on stuff that might not have been of interest to all that many=20 folks. In reply to your comments, I don't yet understand how the=20 nonlinearity acts and how it should mathematically be=20 treated. 
Hi Brett,
 
    I would be quite happy to 'go public' if no one= =20 else objects?  
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I'm=20 uncomfortable with taking the approach that because there exist some fairl= y=20 small (I think) nonlinear effects, then no quantitative analysis can be va= lid=20 at all.  Although it's somewhat beyond
my experience, I believe t= hat=20 feedback designers today routinely deal with highly nonlinear, time-varyin= g,=20 and stochastic system variables and still are able to obtain quite useful=20 results.   If they couldn't there would be a lot fewer airplanes= out=20 there and our cars wouldn't handle as well.
    Read through the papers on Randall's Website?
    
    Your car analogy misses the point. We are conce= rned=20 mostly with microscopic as opposed to macroscopic variations.
 
    The mechanical properties of springs have a 'fi= ne=20 structure' of discontinuous steps, a bit like ferro magnetic domains. This g= ives=20 small 'step function' variations and limits the ultimate performance of=20 seismometers, clocks, MEMS devices, etc. The macroscopic propertie= s=20 are also not quiite linear and are time dependant. Hooke's Law is only an=20 approximation.
    
    How would you suggest incorporating step functi= ons=20 which are random in time, sense and amplitude into the calculations / proper= ties=20 of a feedback loop? The stochastic processes you mentioned?
 
    Regards,
 
    Chris Chapman
    
Subject: Re: fine structure nonlinearity vs dithering From: Charles R Patton charles.r.patton@........ Date: Fri, 08 Feb 2008 22:01:59 -0800 Hi Chris, My thought experiment goes something like this. If one dithers the instrument at the A/D sample frequency (let that be Fc) , then effectively one has created a mixer where the molecular slip/stiction ends up as sidebands of Fc. That spectrum would trend to zero at zero frequency, much as a sigma-delta A/D does. So if the resulting A/D spectrum is lo-pass filtered, the low frequency response spectrum is improved as the filter is cutting off the stiction generated noise sidebands surrounding Fc. I would surmise that Brett could model this as a switching (or sampling) mixer with co-injected random noise with a noise spectrum matching the known molecular stiction spectrum numbers Randall could supply from his observations. Brett, I would argue that you can’t have linear force feedback in the face of stiction-like elements. At the amplitude level of the stiction, the feedback will reflect the discontinuities. I.e., if the force feedback by definition is linear, then it has to linearly follow the discontinuities. The way we blur this is to generally ignore the small imperfections and assume macro properties where all the discontinuities blur into smooth motion (or set the frequency response bandwidth less than the frequency of the noise spectrum of the stiction.) But the discussion here is exactly whether we can legitimately do this if what we’re interested in is the very small movements of seismic activity that may be comparable in scale, or perhaps smaller than the molecular effects causing the slip/stick phenomenon. Which also brings me in round-robin fashion to the reason for dithering – it can supply that “blurring” (both in frequency and motion) function for the force-feedback to work with. Now for the sanity check, – comments, please. Regards, Charles R. Patton ChrisAtUpw@....... wrote: > In a message dated 09/02/2008, Brett3mr@............. writes: > > Charles, > I'm very glad to hear that you're interested in following the > discussion. My only concern had been that we were taking up > bandwidth on stuff that might not have been of interest to all that > many folks. In reply to your comments, I don't yet understand how > the nonlinearity acts and how it should mathematically be treated. > > Hi Brett, > > I would be quite happy to 'go public' if no one else objects? > > I'm uncomfortable with taking the approach that because there exist > some fairly small (I think) nonlinear effects, then no quantitative > analysis can be valid at all. Although it's somewhat beyond > my experience, I believe that feedback designers today routinely > deal with highly nonlinear, time-varying, and stochastic system > variables and still are able to obtain quite useful results. If > they couldn't there would be a lot fewer airplanes out there and our > cars wouldn't handle as well. > > Read through the papers on Randall's Website? > > Your car analogy misses the point. We are concerned mostly with > microscopic as opposed to macroscopic variations. > > The mechanical properties of springs have a 'fine structure' of > discontinuous steps, a bit like ferro magnetic domains. This gives small > 'step function' variations and limits the ultimate performance of > seismometers, clocks, MEMS devices, etc. The macroscopic properties are > also not quiite linear and are time dependant. Hooke's Law is only an > approximation. > > How would you suggest incorporating step functions which are random > in time, sense and amplitude into the calculations / properties of a > feedback loop? The stochastic processes you mentioned? > > Regards, > > Chris Chapman > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Dampng anharmonicity and Seismometry From: Randall Peters PETERS_RD@.......... Date: Sat, 09 Feb 2008 08:44:28 -0500 Too all: For reason of its length and other properties, I previously resisted supplying to the listserve the comments which follow. It appears now appropriate to mention them. Damping Anharmonicity and Seismometry The fine structure of the otherwise smooth (Hooke’s law) potential invalidates the linear (viscous) damping model used to describe simple harmonic oscillation. There are few mechanical systems that even come close to being in agreement with it. This is the case even at substantial amplitudes of oscillation, if the frequency is low—which means that nonlinear processes dominate the damping of seismic instruments in the regime where many now with frustrations want to go to study the earth. An important feature involves ‘self-similarity’, the hallmark of fractal (complex, chaotic) systems. Thus there are properties of even the (huge) earth itself that are similar to what is found in a (small) seismometer. In some respects it is conceptually easier to envision what goes on inside the earth. Our planet is like a multiply-cracked hard-boiled egg. The influence of the tidal forces of sun and moon are vitally significant to its dynamics. One way to think about this is as follows. Roll the hard boiled egg between your hands; as the shell fragments undergo rapid snap, crackle, pops (ala subduction of plates in the earth), the.egg must itself oscillate after each event. A ‘local ping’ of the egg will cause oscillations that persist longer than the oscillations caused by the ‘tidal’ rolling. In similar manner, a large earthquake is followed by long lived eigenmode oscillations. For example, the earth rang like a bell for weeks after the great Andeman-Sumatra earthquake. To believe that it does not also ‘ring’ due to rapid relaxation after a snap, crackle, or pop is to ignore the physics. Those of us trained in solid state physics know that the earth must oscillate all the time (due to its temperature) over the full range of admissible states; i.e., the so-called ‘density of states’. It was Einstein’s analysis of the heat capacity of solids along these lines that constituted one part of the modern physics revolution of the last century. So what is the primary difference between the two oscillation cases just mentioned. First of all, as was noted, the large amplitude motions in which the system ‘skates’ over the fine structure ‘bumps’ is more ‘monochromatic’ (longer lived). Just because the coherence time of the lower level ones is much shorter doesn’t mean they are non-existent. It means they are harder to observe. With my cumulative spectral power (CSP) analysis they are much easier to study. As compared to the power spectral density (PSD) approach, it is much better suited to the manner in which the eye/brain is able to assess information. The CSP allows fine structure of frequency domain type to be readily seen without having to resort to the more complicated ‘waterfall’ methods of conventional spectral type. There’s another conceptual analogy that I have used. Imagine yourself on a gravel road having fine structure (not smooth, but with washboard features that always develop over time). As long as you move at the right speed (not too fast, not too slow) the motion at these large levels allows one to ‘negotiate’ the road. If in a shallow depression, one can travel back and forth (first forward, then in reverse) ‘skating’ over the ‘fine structure’. If however, you get too slow near the bottom, you will get hung up in one of the localized minima. This is precisely what happens with a force-balance seismometer when trying to observe low energy earth motions. The force-balance instrument is without equal for looking at earthquakes all over the world, but in my opinion it will never yield insights into the physics I’ve been recently researching. For example, the VolksMeter allows me to look at diurnal and seasonal changes of importance. Most recently I’ve discovered that there is energy exchange between the eigenmodes and the microseisms. Nobody to my knowledge has previously postulated this. I have also with this pendulum seen in Larry Cochrane’s data the terdiurnal tide having a period of 8 hours. The 12-h and 24-h components are easily seen with a variety of instruments like strain gauges; but the terdiurnal component was previously seen almost solely in meteorological (upper atomosphere) measurements using radar. In the case of mechanical oscillators, the potential well in general has features having some similarity to the various analogies that I’ve mentioned. The details of the fine structure have not been worked out; since internal friction is not understood from first principles. I have postulated that individual ‘grain boundary’ regions (ala Chris Chapman’s comment concerning the analogy with magnetic domains) become altered when strain energies exceed certain thresholds. If that 'quantum' postulate could be proven, it would probably result in a Nobel prize; however, the challenge of reproducibility in experiments is Herculean (and nobody other than myself is to my knowledge yet trying to prove the matter). The problem requires extreme patience, because the frequencies required for study are so low. Thus the lifetime of the investigator comes into play. Concerning the friction ‘force’— Linear damping in the equation of motion causes the friction force to be sinusoidal and shifted in phase by 90 degrees from the sinusoidal displacement (proportional to velocity). It also requires that the quality factor Q as a function of natural frequency f be of the form Q proportional to f. Seismometers DO NOT conform to this! Gunar Strekeisen was apparently the first person to observe this nonconformity, while he was a grad-student working with a LaCoste spring. What he observed was Q proportional to f-squared. This quadratic dependence is the hallmark of hysteretic damping (that engineers have known about for a long time, but for which physicists are almost universally ignorant). What I have shown through experimentation is that the friction force is not sinusoidal. It is more nearly an attenuating square wave! Its amplitude falls off as the amplitude of the displacement decreases, thus giving rise to an exponential decay. Just because the decay is exponential, does not mean the damping is linear!! Only the fundamental of the Fourier component of this square wave friction is important in establishing the Q. Thus the nonlinear damping masquerades as linear even though it is far from being so! Among other of its features, there is no damping redshift; i.e., the natural frequency does not decrease as the amount of damping increases. Randall Subject: Cumulative Spectral Power example From: Randall Peters PETERS_RD@.......... Date: Sat, 09 Feb 2008 10:34:21 -0500 In my previous submission I alluded to how the CSP allows one to readily observe time dependent changes in the spectral content of the earth's motions. Of course earthquakes are among the most important of those, but it is incredible how little attention is given to the details of their spectral nature. There is great to-do about the arrival times of P, S and surface waves; but it's as though folks only want to know (i) how big, (ii) how deep, and (iii) where did it happen. There is SO MUCH more to be gleaned from the records, if the calculations were simply done. On my webpage that was just generated at http://physics.mercer.edu/hpage/evolve.html I show one example of the wealth of information that is available to us and which is not yet being mined! Why there has not been at least some attention given to more routine PSD calculations is mind boggling. To those of you who would want to similarly calculate PSD/CSP curves from data recorded with your own seismometer--by means of the LabView algorithm that Dr. Lee produced (used to generate the figure in the above reference)--John has indicated his willingness to provide the program free of charge to anyone who would simply send him an email. I don't know to what extent that code can be simply packaged in a zip form for email attachment; it was in my case transferred to my computer with a flash drive. Randall Subject: Seismograph noise problem From: Larry Conklin lconklin@............ Date: Sat, 09 Feb 2008 11:24:17 -0500 Hi all, I think I must have a haunted system. I have been running a SG seismometer for about seven years. The mechanical design is very similar to the one described on the PSN web site, and I am Using Larry's electronics board. Over nearly the entire time I have been running this system I have had repeated episodes of extreme noise or some sort of spurious signal. When It occurs, the problem persists with little change for anywhere from a few days to several months, and then seems to fade away over the course of several days. The problem reoccurred a couple of weeks ago. It was apparently precipitated by the disturbance I caused by adjusting the leveling screw to recenter the pendulum (something I do frequently, with no problem). Before making the adjustment, I was getting about +/- 30 counts of signal excursion from the low frequency channel. Immediately after, I got around +/- 350 counts, rendering the system essentially worthless. I have put a lot of effort into trying to figure out what is going on, to no avail. In one of the previous episodes, I disconnected the power to the oscillator that drives the antenna plate, and opened the loop for the feedback damping. There was no significant change in the output, which led me at the time to conclude that there must either be something wrong with the electronics board, or some sort of electrical/magnetic pick-up. Despite a lot of diddling around, I couldn't determine a cause, and eventually, the system settled down without my having done anything specific to fixing it. And, neither theory fits well with this current episode, which started when I mechanically disurbed the sensor a little by adjusting the leveling. So, do I have a poltergeist detector when I thought I had a seismometer? I threw together a web page that shows the onset of the problem, as well as short time intervals before and after the problem started this time. If anyone cares to take a look at it and offer their thoughts (or condolences), I'd like to hear them. http://home.twcny.rr.com/lwconklin/Seismograph_Noise_Problem.html Larry Conklin Liverpool, NY lconklin@............ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismograph noise problem From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Sat, 09 Feb 2008 16:35:44 +0000 Hi Do you have a volcano near by ? Because an volcano can be an source of great noise that can last for months, even years. Regards. --=20 J=F3n Fr=EDmann http://www.jonfr.com http://earthquakes.jonfr.com http://www.net303.net http://www.mobile-coverage.com/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: unsubscribe From: "John Vidale" john.vidale@......... Date: Sat, 9 Feb 2008 09:05:37 -0800 unsubscribe unsubscribe
Subject: Re: Seismograph noise problem From: Larry Conklin lconklin@............ Date: Sat, 09 Feb 2008 13:19:08 -0500 Hi Jon, Well the nearest volcano to me is probably in your native Iceland, or possibly Mt. Ranier in Washington state. In either case, several thousand miles away. So, I think I can rule that out as a cause. Larry Jón Frímann wrote: > Hi > > Do you have a volcano near by ? Because an volcano can be an source of > great noise that can last for months, even years. > > Regards. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Dampng anharmonicity and Seismometry From: Brett Nordgren Brett3mr@............. Date: Sat, 09 Feb 2008 13:51:25 -0500 Randall, I'd like to use an adaptation of your analogy to try to make a very non-rigorous argument, though I believe an accurate one, as to how a specific type of force-balance instrument deals with potholes in your road. I am here making the assumption that your analogy can be applied to the spring force in a vertical device. I will also assume that the pothole forces are very small compared with the spring force and just represent small variations from linearity. I realize that your example probably applies to much lower frequencies and much smaller motions than the regime I am describing and it's not surprising that you can discover some 'interesting' issues down there. It is probably true that there is a practical limit as to how much low frequency sensitivity you can build into a vertical (i.e. a device which depends on a spring). I gather that most verticals give up once you get beyond a hundred seconds or so. For the specific case of a force balance vertical designed to be flat to velocity, the feedback in the flat portion of the instrument response is dominated by feedback via the derivative branch. I will assume that here we are using ideal components, and that the spring is the only non linear element. We are monitoring the position of the test mass, greatly amplifying that measurement and differentiating it to achieve a large signal proportional to the velocity of the mass. That signal we are then sending to a forcing coil which pushes on the mass so as to oppose its motion. To begin with we are moving smoothly down the road and everything is more or less in balance. Now we hit one of the potholes and the mass motion suddenly slows very slightly. As a result, the derivitave feedback branch quickly responds by reducing its resistance to the motion, allowing the spring-mass to more easily rise out of the pothole. Then when the velocity suddenly begins to rise as we come back onto the flat road, the feedback quickly increases the resisting force to help keep the velocity constant. The feedback effectively makes the pothole appear shallower than it realy is. Quantitatively, the apparent 'depth' of the pothole is reduced by the strength of the feedback (loop gain). In a good design that should be over 100 and possibly much greater. The pothole appears to be only 1% or less as 'deep' as it was without feedback. I should mention that the above discussion will also apply to any other small damping forces, linear or non linear. Brett At 08:44 AM 2/9/2008 -0500, you wrote: > There's another conceptual analogy that I have used. Imagine yourself > on a gravel road >having fine structure (not smooth, but with washboard features that always >develop over >time). As long as you move at the right speed (not too fast, not too >slow) the motion at >these large levels allows one to 'negotiate' the road. If in a shallow >depression, one >can travel back and forth (first forward, then in reverse) 'skating' over >the 'fine >structure'. If however, you get too slow near the bottom, you will get >hung up in one of >the localized minima. This is precisely what happens with a force-balance >seismometer >when trying to observe low energy earth motions. > Randall __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: fine structure nonlinearity vs dithering From: Brett Nordgren Brett3mr@............. Date: Sat, 09 Feb 2008 14:04:05 -0500 At 11:29 PM 2/8/2008 -0500, you wrote: > > >Hi Brett, > > I would be quite happy to 'go public' if no one else objects? >I'm uncomfortable with taking the approach that because there exist some >fairly small (I think) nonlinear effects, then no quantitative analysis >can be valid at all. Although it's somewhat beyond >my experience, I believe that feedback designers today routinely deal with >highly nonlinear, time-varying, and stochastic system variables and still >are able to obtain quite useful results. If they couldn't there would be >a lot fewer airplanes out there and our cars wouldn't handle as well. > Read through the papers on Randall's Website? > > Your car analogy misses the point. We are concerned mostly with > microscopic as opposed to macroscopic variations. > > The mechanical properties of springs have a 'fine structure' of > discontinuous steps, a bit like ferro magnetic domains. This gives small > 'step function' variations and limits the ultimate performance of > seismometers, clocks, MEMS devices, etc. The macroscopic properties are > also not quiite linear and are time dependant. Hooke's Law is only an > approximation. Certainly for the tiny MEMS stuff the world looks a lot different, and the effects may be an important consideration in a successful design. Otherwise, I'm not yet sure I see why I should get out my microscope to look for the fine structure effects when there are plenty of other error terms which I think are quite a lot larger. For example, in the STM-8 vertical the spring has a temperature sensitivity which amounts to about 200,000 nm / deg C. > > How would you suggest incorporating step functions which are random > in time, sense and amplitude into the calculations / properties of a > feedback loop? The stochastic processes you mentioned? > I'm no nonlinear guru, but there are approaches out there that should be able to deal with it. The easiest, is to prove that the effects are small enough to not affect the results and treat the system as linear. Deep down that's what I really think is the situation, though am certainly not in a position to prove it. It could be that the effects show up as some form of noise in the system, which is straight forward to analyze. Many feedback systems today are digital, in which all the signals are quantized, so dealing with that sort of issue, in general, hasn't posed any insurmountable problems to the design community. In fact they are doing things with digital feedback that could never have been considered otherwise, like making airplanes appear to be well behaved which without the feedback are inherently unstable and impossible to fly. You could, on paper, start by treating the system as linear, then inject a signal of random step functions at the appropriate point in the feedback loop to simulate the situation and look at the effect at the output. That would probably be how I would first approach the analysis. Brett __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: feedback limitations due to damping anharmonicity From: Randall Peters PETERS_RD@.......... Date: Sat, 09 Feb 2008 14:35:10 -0500 Brett, I don't see an obvioius 'showstopper' with what you've mentioned, but then I certainly don't understand all the nuances. Let me give you one of the thoughts that I posed on this matter the better part of a decade ago. The following is copied from one of my webpages: 3.3 Gedanken to illustrate that limitations exist Lest one believe that force-balance feedback is infinitely superior to conventional seismometry, consider the following logic. Why even bother with the leaf-spring that is commonly used to support the test mass in these instruments? Why not just add a feedback network to a solid state mass balance instrument that works with resistive strain gauges? Place a big test mass on the pan of the modified mass balance (mmb), add a magnetic transducer of some type to provide a significant lifting force on the mass, and ``voila''-with proper feedback adjustment we suddenly can see earthquakes with the simplest of instruments. Hopefully everyone will quickly recognize the folly of this reasoning and know that such a modified mass measuring instrument is not capable of functioning as a bonafide seismometer. But why? The answer to this question lies in the following observation. System adaptability is no better than the integrity of the ``spring'' used in generation of the error signal. As noted earlier, any error signal requires the measurement of strain. In the case of the hypothetical modified mmb, the ``spring'', in the absence of feedback, has an exceedingly large k. In the case of the W/S leaf-spring seismometer, the leaf has a considerably larger k than that of the conventional seismometer. Can electronics soften even the hardest springs? The answer is obviously no! What are the limitations to softening? I submit to the reader that there are a host of unanswered questions in the matter. It is easy to see that electronics limitations (addressed earlier) pose an ultimate upper limit on the size of k. But anelasticity of the support is probably even more important than the electronics-and the problems borne of it are mostly unstudied. This is true in spite of the fact that practictioners understand that an instrument must be allowed to settle for some time after initial loading, before it becomes dependable. This settling is necessary to minimize the effects of anelasticity, through a type of work-hardening. There is a factor in all this that is unavoidable and of much greater influence than I ever expected until some experiments that I did in the last year--concerned with creep. The results will be reported in the Chapter 1 that I wrote titled "Building on old foundations with new technologies", of Nova's "Science Education in the 21st Century"--due out this quarter. There is apparently no level below which creep isn't significant and it's influence depends on which way the temperature was moving at the time the system is observed (total temperature swings of only about 5 C over 24 h.) I found significant, peculiar disruptions due to creep at energy levels of the pendulum at only 10^(-12) J. Bottom line--engineering the feedback network to compensate for the multiplicity of anomalous possibilities appears to me to be a staggering proposition. My own opinion is that it is best to let the seismometer 'find its own best equilbirium', rather than forcing it into the 'one preferred by the chosen point of the feedback circuitry'. Why mess with mother nature's preference? Randall Subject: Re: Seismograph noise problem From: ChrisAtUpw@....... Date: Sat, 9 Feb 2008 17:22:38 EST In a message dated 09/02/2008, lconklin@............ writes: I have put a lot of effort into trying to figure out what is going on, to no avail. In one of the previous episodes, I disconnected the power to the oscillator that drives the antenna plate, and opened the loop for the feedback damping. There was no significant change in the output, which led me at the time to conclude that there must either be something wrong with the electronics board, or some sort of electrical/magnetic pick-up. Despite a lot of diddling around, I couldn't determine a cause, and eventually, the system settled down without my having done anything specific to fixing it. And, neither theory fits well with this current episode, which started when I mechanically disurbed the sensor a little by adjusting the leveling. I threw together a web page that shows the onset of the problem, as well as short time intervals before and after the problem started this time. If anyone cares to take a look at it and offer their thoughts (or condolences), I'd like to hear them. Hi Larry, The problem seems to be with the first opamp or it's circuit. Clean the input connectors with fine wire wool and coat them with vaseline. If the resistors are NOT metal film, check them for damage / the correct resistance, maybe replace the input circuit ones with metal film resistors. This could simply be a faulty resistor. Visually inspect the solder joints with a magnifying glass for any which appear faulty. You can get a solder fault called crevice corrosion, when corrosion creeps in between the copper board and the solder joints. Remove one solder blob on say a resistor and then scratch the tinned area with a knife. If you have crevice corrosion, the solder will peel off leaving a dark brown oxide film on the copper strip. It could also be that the opamp is faulty. Does it unplug, or is it soldered in? Can you replace it easily? You can buy a spray can of freezing fluid. You monitor the signal output and then spray freeze the components in turn. If one is faulty, you are likely to see a large change in the output signal. If the board gets damp while in use, you can brush coat it with single pack polyurethane varnish for protection. Regards, Chris Chapman
In a message dated 09/02/2008, lconklin@............ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I have=20 put a lot of effort into trying to figure out what is going on, to no=20 avail.  In one of the previous episodes, I disconnected the power to=20= the=20 oscillator that drives the antenna plate, and opened the loop for the feed= back=20 damping.  There was no significant change in the output, which led me= at=20 the time to conclude that there must either be something wrong with the=20 electronics board, or some sort of electrical/magnetic pick-up.  = ;=20 Despite a lot of  diddling around, I couldn't determine a cause, and=20 eventually, the system settled down without my having done anything specif= ic=20 to fixing it.  And,
neither theory fits well with this current=20 episode, which started when I mechanically disurbed the sensor a little by= =20 adjusting the leveling.

  I threw together a web page that sho= ws=20 the onset of the problem, as well as short time intervals  before and= =20 after the problem started this time.  If anyone cares to take a look=20= at=20 it and offer their thoughts (or condolences), I'd like to hear=20 them.
Hi Larry,
 
    The problem seems to be with the first opamp or= =20 it's circuit.
 
    Clean the input connectors with fine wire wool=20= and=20 coat them with vaseline.
    If the resistors are NOT metal film, check them= for=20 damage / the correct resistance, maybe replace the input circuit ones with m= etal=20 film resistors. This could simply be a faulty resistor.
    Visually inspect the solder joints with a=20 magnifying glass for any which appear faulty.
    You can get a solder fault called crevice=20 corrosion, when corrosion creeps in between the copper board and the so= lder=20 joints. Remove one solder blob on say a resistor and then scratch the tinned= =20 area with a knife. If you have crevice corrosion, the solder will peel off=20 leaving a dark brown oxide film on the copper strip.
    It could also be that the opamp is faulty.= =20 Does it unplug, or is it soldered in? Can you replace it easily?
 
    You can buy a spray can of freezing fluid. You=20 monitor the signal output and then spray freeze the components in turn. If o= ne=20 is faulty, you are likely to see a large change in the output signal.
    If the board gets damp while in use, you can br= ush=20 coat it with single pack polyurethane varnish for protection.
 
    Regards,
 
    Chris Chapman
Subject: Re: fine structure nonlinearity vs dithering From: ChrisAtUpw@....... Date: Sat, 9 Feb 2008 22:11:01 EST In a message dated 09/02/2008 19:03:59 GMT Standard Time, Brett3mr@............. writes: Otherwise, I'm not yet sure I see why I should get out my microscope to look for the fine structure effects when there are plenty of other error terms which I think are quite a lot larger. For example, in the STM-8 vertical the spring has a temperature sensitivity which amounts to about 200,000 nm / deg C. Hi Brett, I am not saying thet there are not other effects which can and do limit the sensitivity / stability. You could replace the steel spring by a NiSpanC one? The extreme sensitivity to temperature suggests that this would be highly desirable and probably beyond the stability that you could achieve with a thermostat. > How would you suggest incorporating step functions which are random > in time, sense and amplitude into the calculations / properties of a > feedback loop? The stochastic processes you mentioned? I'm no nonlinear guru, but there are approaches out there that should be able to deal with it. The easiest, is to prove that the effects are small enough to not affect the results and treat the system as linear. Deep down that's what I really think is the situation, though am certainly not in a position to prove it. It could be that the effects show up as some form of noise in the system, which is straight forward to analyze. The effects are not insignificant and involve a shift in the mean level. Many feedback systems today are digital, in which all the signals are quantized, so dealing with that sort of issue, in general, hasn't posed any insurmountable problems to the design community. In fact they are doing things with digital feedback that could never have been considered otherwise, like making airplanes appear to be well behaved which without the feedback are inherently unstable and impossible to fly. Sure, but the digitisation steps are then small compared to the background noise signals / control signals. If the steps are large, you may well not be able to stabilise the system, or you are left with the output switching between two levels. You could, on paper, start by treating the system as linear, then inject a signal of random step functions at the appropriate point in the feedback loop to simulate the situation and look at the effect at the output. That would probably be how I would first approach the analysis. Noise generally has a zero average level. These are steps in the zero level. One of the costs of making long period seismometers is in reducing / controlling the inherent noise in the spring. Regards, Chris Chapman
In a message dated 09/02/2008 19:03:59 GMT Standard Time,=20 Brett3mr@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Otherwise, I'm not yet sure I see why I should get out my microsc= ope to=20 look for the fine structure effects when there are plenty of other error t= erms=20 which I think are quite a lot larger.  For example, in the STM-8 vert= ical=20 the spring has a temperature sensitivity which amounts to about 200,000 nm= /=20 deg C.
Hi Brett,
 
    I am not saying thet there are not other effect= s=20 which can and do limit the sensitivity / stability. You could replace the st= eel=20 spring by a NiSpanC one? The extreme sensitivity to temperature suggests=20 that this would be highly desirable and probably beyond the stability t= hat=20 you could achieve with a thermostat.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>>     How would you suggest incorporating step=20 functions which are random
> in time, sense and amplitude into the=20 calculations / properties of a
> feedback loop? The stochastic=20 processes you mentioned?

I'm no nonlinear guru, but there are=20 approaches out there that should be able to deal with it.  The easies= t,=20 is to prove that the effects are small enough to not affect the results an= d=20 treat the system as linear.  Deep down that's what I really think is=20= the=20 situation, though am certainly not in a position to prove it.  It cou= ld=20 be that the effects show up as some form of noise in the system, which is=20 straight forward to analyze.
    The effects are not insignificant and involve a= =20 shift in the mean level.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Many=20 feedback systems today are digital, in which all the signals are quantized= , so=20 dealing with that sort of issue, in general, hasn't posed any insurmountab= le=20 problems to the design community.  In fact they are doing things with= =20 digital feedback that could never have been considered
otherwise, like= =20 making airplanes appear to be well behaved which without the feedback are=20 inherently unstable and impossible to fly.
    Sure, but the digitisation steps are=20 then small compared to the background noise signals / control signals.=20= If=20 the steps are large, you may well not be able to stabilise the system, or yo= u=20 are left with the output switching between two levels.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>You=20 could, on paper, start by treating the system as linear, then inject a sig= nal=20 of random step functions at the appropriate point in the feedback loop to=20 simulate the situation and look at the effect at the output. That would=20 probably be how I would first approach the analysis.
    Noise generally has a zero average level. These= are=20 steps in the zero level. One of the costs of making long period seismometers= is=20 in reducing / controlling the inherent noise in the spring.
 
    Regards,
 
    Chris Chapman
Subject: Re: Dampng anharmonicity and Seismometry From: ChrisAtUpw@....... Date: Sat, 9 Feb 2008 22:21:57 EST In a message dated 09/02/2008, Brett3mr@............. writes: I will also assume that the pothole forces are very small compared with the spring force and just represent small variations from linearity. Hi Brett, This is the trouble. They are NOT small compared to the restoring force. To get a really long period, the gradient of the spring force with position is nearly flat, but you are still offsetting the full mass Mg. Consequently the deflection produced by a small step change in the spring properties can produce a large mass movement. Note that noise is assumed to have a mean level of zero. The effects we have to cope with are discreet steps in the zero level. Regards, Chris Chapman
In a message dated 09/02/2008, Brett3mr@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>  I=20 will also assume that the pothole forces are very small compared with the=20 spring force and just represent small variations from=20 linearity.
Hi Brett,
 
    This is the trouble. They are NOT small compare= d to=20 the restoring force.
    To get a really long period, the gradient of th= e=20 spring force with position is nearly flat, but you are still offsetting the=20= full=20 mass Mg.
    Consequently the deflection produced by a small= =20 step change in the spring properties can produce a large mass=20 movement. 
    Note that noise is assumed to have a mean level= of=20 zero. The effects we have to cope with are discreet steps in the zero=20 level.
 
    Regards,
 
    Chris Chapman
Subject: Re: Seismograph noise problem From: Larry Conklin lconklin@............ Date: Sat, 09 Feb 2008 23:32:22 -0500 Hi Chris, Thanks for your suggestions. I haven't yet made any serious attempt to work the current manifestation of this problem, mostly for lack of new ideas for something new to try. But a couple of years ago when the same sort of thing happened, I did replace the input op amp and didn't see any obvious change. My theory at the time was that since I can see problems in both outputs, whatever is causing it must be upstream of where the two channels diverge, and that doesn't leave much. The chip is soldered to the board, so all of those connections got a workover as a byproduct of the change. And, after changing the chip, I did a thorough cleaning of the board to get rid of stray solder flux. The other possibility would be in the power supply. I pretty much ruled that out by measuring the power at right at the op-amp pins on all of the chips individually. Thought a decoupling cap might be getting flakey. But everything looked flat to within +/- 10 mv, which is the resolution limit of my inexpensive DVM. Don't know what sort of resistors are used in the board, other than they certainly aren't cheap composition resistors. I'll take a closer look at them, and maybe I should resolder the joints in the input stage. But, the board looks to be very well made, and I'd be pretty surprised if there was a bad joint. It looks like it was professionally built, probably with a wave soldering machine. I have also tried the freeze spray idea. It seemed like I could spray the board pretty much anywhere and the output would jump all over the place. So, I wasn't able to draw any useful conclusions from the experiment. If the problem really is something in the circuit board, I can't account for the fact that things were running ok right up to the exact moment that I disturbed it, as you can see from the data record. I suppose it is possible that the large signal excursion caused by walking up to the sensor and making the adjustment aggravated some latent problem, but I have a hard time persuading myself that it's likely. I have recorded a quakes that drove the thing to saturation and never have seen any similar consequence. I don't have to touch the board, the case or the cables to do a leveling adjustment, just tweak the screw with a screwdriver. I guess my most convincing theory at the moment is that there is a poltergeist living in my basement. Larry ChrisAtUpw@....... wrote: > In a message dated 09/02/2008, lconklin@............ writes: > > I have put a lot of effort into trying to figure out what is going > on, to no avail. In one of the previous episodes, I disconnected > the power to the oscillator that drives the antenna plate, and > opened the loop for the feedback damping. There was no significant > change in the output, which led me at the time to conclude that > there must either be something wrong with the electronics board, or > some sort of electrical/magnetic pick-up. Despite a lot of > diddling around, I couldn't determine a cause, and eventually, the > system settled down without my having done anything specific to > fixing it. And, > neither theory fits well with this current episode, which started > when I mechanically disurbed the sensor a little by adjusting the > leveling. > > I threw together a web page that shows the onset of the problem, > as well as short time intervals before and after the problem > started this time. If anyone cares to take a look at it and offer > their thoughts (or condolences), I'd like to hear them. > > Hi Larry, > > The problem seems to be with the first opamp or it's circuit. > > Clean the input connectors with fine wire wool and coat them with > vaseline. > If the resistors are NOT metal film, check them for damage / the > correct resistance, maybe replace the input circuit ones with metal film > resistors. This could simply be a faulty resistor. > Visually inspect the solder joints with a magnifying glass for any > which appear faulty. > You can get a solder fault called crevice corrosion, when corrosion > creeps in between the copper board and the solder joints. Remove one > solder blob on say a resistor and then scratch the tinned area with a > knife. If you have crevice corrosion, the solder will peel off leaving a > dark brown oxide film on the copper strip. > It could also be that the opamp is faulty. Does it unplug, or is it > soldered in? Can you replace it easily? > > You can buy a spray can of freezing fluid. You monitor the signal > output and then spray freeze the components in turn. If one is faulty, > you are likely to see a large change in the output signal. > If the board gets damp while in use, you can brush coat it with > single pack polyurethane varnish for protection. > > Regards, > > Chris Chapman __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismograph noise problem From: Roger Sparks rsparks@.......... Date: Sat, 09 Feb 2008 22:20:31 -0800 Hi Larry, Sorry that you are having the noise problem after adjusting your seismometer. I had a similar problem for a while that was caused by poor contact to the solid surface. In my case, I was going through a rug to a concrete surface. For a while, one leg did not properly contact the hard surface. The microsiems caused a rocking that displayed as noise. I did not know I had a problem until an FFT of the noisy signal showed a higher frequency spectra that was not present in the older traces. The fix was simply to beef up my penetrations through the rug. Are you using a three leg mount? Are the contacts to the hard surface made with points? Do you have a locking nut or other mechanism to fix the adjusting screws after adjustment? Do you have any loose parts that could "rock" due to the microsiems? Do you "set" your seismometer after adjustment by putting extra pressure to help reset the contact points? Good luck on the repairs, Roger > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 3 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Seismograph noise problem > From: Larry Conklin > Date: Sat, 09 Feb 2008 11:24:17 -0500 > > Hi all, > > I think I must have a haunted system. I have been running a SG > seismometer for about seven years. The mechanical design is very > similar to the one described on the PSN web site, and I am Using Larry's > electronics board. Over nearly the entire time I have been running this > system I have had repeated episodes of extreme noise or some sort of > spurious signal. When It occurs, the problem persists with little > change for anywhere from a few days to several months, and then seems to > fade away over the course of several days. The problem reoccurred a > couple of weeks ago. It was apparently precipitated by the disturbance > I caused by adjusting the leveling screw to recenter the pendulum > (something I do frequently, with no problem). Before making the > adjustment, I was getting about +/- 30 counts of signal excursion from > the low frequency channel. Immediately after, I got around +/- 350 > counts, rendering the system essentially worthless. > > I have put a lot of effort into trying to figure out what is going on, > to no avail. In one of the previous episodes, I disconnected the power > to the oscillator that drives the antenna plate, and opened the loop for > the feedback damping. There was no significant change in the output, > which led me at the time to conclude that there must either be something > wrong with the electronics board, > or some sort of electrical/magnetic pick-up. Despite a lot of diddling > around, I couldn't determine a cause, and eventually, the system settled > down without my having done anything specific to fixing it. And, > neither theory fits well with this current episode, which started when I > mechanically disurbed the sensor a little by adjusting the leveling. > > So, do I have a poltergeist detector when I thought I had a seismometer? > I threw together a web page that shows the onset of the problem, as > well as short time intervals before and after the problem started this > time. If anyone cares to take a look at it and offer their thoughts (or > condolences), I'd like to hear them. > > http://home.twcny.rr.com/lwconklin/Seismograph_Noise_Problem.html > > Larry Conklin > Liverpool, NY > lconklin@............ > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: nature of the mesoscopic nonlinearity From: Randall Peters PETERS_RD@.......... Date: Sun, 10 Feb 2008 09:14:18 -0500 Brett, I've been able now to give enough thought to your comments about "potholes" to provide the following response. Chris 'hit the nail on the head' with his statement "... to cope with discrete steps in the zero level". In other words, if the term is at all appropriate, it is not your 'average' pothole as found in northern climate highways where temperatures are at times routinely below freezing. The 'potholes of seismic type' are 'diffusive' in terms of both temperature and stress. There is a paper of mine at http://arxiv.org/html/physics/0307016 titled "Harmonic oscillator potential to describe internal dissipation". As discussed there, the potential function is not fixed. As the seismometer mass moves back and forth, the equilibrium position, to which it would go if motion were suppressed, shifts back and forth. This is the basis for hysteresis--reason the term 'hysteretic damping' is appropriate. The problem with this hysteresis is that the mesoanelastic steps associated with it are not themselves fixed. My study of creep mentioned earlier is proof positive of that fact. What happens is the strain energy that accumulates at polycrystalline grain boundaries causes a rearrangement of the atoms (redistribution of the defect structures) when various thresholds are exceeded. Such is the nature of work-hardening. In primary creep (exponential variation), the material is trying to arrest the changes brought about by the external forcing. 'Success' in so doing results in a conversion to secondary (linear variation) creep. If the temperature were zero--end of story. But temperature serves to undo the hardening and so a 'balance' results between hardening and softening. If the stress levels become large enough, the defect structural reorganizations become much bigger, resulting in cracks and eventual fatigue failure. Truly, what I'm discussing is one of the most important and yet still mysterious of scientific phenomena. Its complexity has so far prohibited understanding of the processes from first principles. Perhaps another analogy is of some related value--that of a non-Newtonian liquid. Maybe you've seen the Mythbusters episode in which they filled a 'small swimming pool' with such a liquid (huge amount of corn starch with water). One of the team was able to easily 'walk on water' across the surface of this mix as long as he moved quickly. But if he tried to do so slowly, he sank all the way to his neck. The more natural example of the same phenomenon is that of quicksand. Still another fascinating example of such complexity is ordinary sea sand mixed with ocean water. If the sand is too dry, it is hard to walk on. Same if the sand is too wet. Get the amount of water just right and you can drive tanks on it! What we're dealing with are the yet-unknown properties of granular materials, which is an advancing frontier of science and engineering. One of my favorite examples is a can of nuts. If you briskly shake a can of mixed nuts the larger ones will migrate toward the upper surface, in seeming defiance of the influence of gravity--because of their interaction with smaller nuts responsible for 'symmetry breaking'. Randall Subject: Re: Seismograph noise problem From: Larry Conklin lconklin@............ Date: Sun, 10 Feb 2008 10:39:43 -0500 Hi Roger, I it very interesting that you have had a similar problem, and I appreciate your suggestions. I my case, the sensor in in the basement, sitting on a concrete floor. Several years ago I epoxied three small aluminum plates to the floor for the settling screws to sit on. My concern at the time was that turning the leveling screw against the concrete was grinding into the floor, leaving concrete dust under the screw. One of the probable flaws in my construction is that the leveling screw is very small (#4) and more than likely not really firm enough. But, when I'm not being "haunted" the thing performs pretty well. Seems like problems stemming from the mechanical design shouldn't be episodic the way I have having them. I am using a 3 point mount, and the other two feet (base of the triangle) are sturdier. One thing that your comments encourage me to revisit is the way the cover over the sensor is made. It is made of 1/4/inch particle board and a little heavy on the heavy side. I is just sitting on the base frame of the sensor, held down by it's own weight. There are soft plastic feet attached where the contact is made to the frame. I don't normally make a point of pressing everything down to reseat things after i adjust it. Never occurred to me to do that. One thing I did try since this last episode started was to put a little piece of tape under each foot, to introduce a little "sqisshyness" to prevent the kind of "micro-rocking" that you apparently had. I didn't see any obvious difference. Guess I'm going to have to embark on a real science project. Larry Roger Sparks wrote: > > Hi Larry, > > Sorry that you are having the noise problem after adjusting your > seismometer. > > I had a similar problem for a while that was caused by poor contact to > the solid surface. In my case, I was going through a rug to a concrete > surface. For a while, one leg did not properly contact the hard > surface. The microsiems caused a rocking that displayed as noise. > > I did not know I had a problem until an FFT of the noisy signal showed a > higher frequency spectra that was not present in the older traces. The > fix was simply to beef up my penetrations through the rug. > > Are you using a three leg mount? Are the contacts to the hard surface > made with points? Do you have a locking nut or other mechanism to fix > the adjusting screws after adjustment? Do you have any loose parts that > could "rock" due to the microsiems? Do you "set" your seismometer after > adjustment by putting extra pressure to help reset the contact points? > > Good luck on the repairs, > > Roger > > >> >> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. >> | Message 3 | >> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' >> Subject: Seismograph noise problem >> From: Larry Conklin >> Date: Sat, 09 Feb 2008 11:24:17 -0500 >> >> Hi all, >> >> I think I must have a haunted system. I have been running a SG >> seismometer for about seven years. The mechanical design is very >> similar to the one described on the PSN web site, and I am Using >> Larry's electronics board. Over nearly the entire time I have been >> running this system I have had repeated episodes of extreme noise or >> some sort of spurious signal. When It occurs, the problem persists >> with little change for anywhere from a few days to several months, and >> then seems to fade away over the course of several days. The problem >> reoccurred a couple of weeks ago. It was apparently precipitated by >> the disturbance I caused by adjusting the leveling screw to recenter >> the pendulum (something I do frequently, with no problem). Before >> making the adjustment, I was getting about +/- 30 counts of signal >> excursion from the low frequency channel. Immediately after, I got >> around +/- 350 counts, rendering the system essentially worthless. >> >> I have put a lot of effort into trying to figure out what is going on, >> to no avail. In one of the previous episodes, I disconnected the >> power to the oscillator that drives the antenna plate, and opened the >> loop for the feedback damping. There was no significant change in the >> output, which led me at the time to conclude that there must either be >> something wrong with the electronics board, >> or some sort of electrical/magnetic pick-up. Despite a lot of >> diddling around, I couldn't determine a cause, and eventually, the >> system settled down without my having done anything specific to fixing >> it. And, neither theory fits well with this current episode, which >> started when I mechanically disurbed the sensor a little by adjusting >> the leveling. >> >> So, do I have a poltergeist detector when I thought I had a >> seismometer? I threw together a web page that shows the onset of the >> problem, as well as short time intervals before and after the problem >> started this time. If anyone cares to take a look at it and offer >> their thoughts (or condolences), I'd like to hear them. >> >> http://home.twcny.rr.com/lwconklin/Seismograph_Noise_Problem.html >> >> Larry Conklin >> Liverpool, NY >> lconklin@............ >> >> >> > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: nature of the mesoscopic nonlinearity From: ChrisAtUpw@....... Date: Sun, 10 Feb 2008 13:17:03 EST In a message dated 10/02/2008, PETERS_RD@.......... writes: I've been able now to give enough thought to your comments about "potholes" to provide the following response. Chris 'hit the nail on the head' with his statement "... to cope with discrete steps in the zero level". In other words, if the term is at all appropriate, it is not your 'average' pothole as found in northern climate highways where temperatures are at times routinely below freezing. The 'potholes of seismic type' are 'diffusive' in terms of both temperature and stress. Hi Brett, This raises another point about practical seismometer performance. 'Instantaneous' shifts in the zero level generate wide bandwidth high amplitudes spikes in a velocity feedback loop. These have to be applied using a coil with a high inductance and can saturate the electronics. Using magnet + plate damping avoids this. Regards, Chris Chapman
In a message dated 10/02/2008, PETERS_RD@.......... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2> =20   I've been able now to give enough thought to your comments about=20 "potholes" to
provide the following response.
Chris 'hit the nail on= the=20 head' with his statement "... to cope with discrete steps in
the zero=20 level".  In other words, if the term is at all appropriate, it is not= =20 your
'average' pothole as found in northern climate highways where=20 temperatures are at times
routinely below freezing.  The 'potholes= of=20 seismic type' are 'diffusive' in terms of
both temperature and=20 stress.
Hi Brett,
 
    This raises another point about=20 practical seismometer performance. 'Instantaneous' shifts in the zero l= evel=20 generate wide bandwidth high amplitudes spikes in a velocity feedback l= oop.=20 These have to be applied using a coil with a high inductance and c= an=20 saturate the electronics. Using magnet + plate damping avoids this.
 
    Regards,
 
    Chris Chapman
Subject: Geophone From: "Dale Hardy" photon1@........... Date: Mon, 11 Feb 2008 12:30:43 +1100 Hi, I am going to add a geophone to my station and just would like ideas = on how best to place one. Thanks Dale
Hi, I am going to add a geophone to my = station and=20 just would like ideas on how best to place one.
Thanks
Dale
Subject: Re: Geophone From: John Lahr johnjan@........ Date: Sun, 10 Feb 2008 18:02:04 -0800 At 05:30 PM 2/10/2008, you wrote: >Hi, I am going to add a geophone to my station and just would like >ideas on how best to place one. >Thanks >Dale Dale, Could you provide a few more details about the geophone and your setting? John __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: nature of the mesoscopic nonlinearity From: Brett Nordgren Brett3mr@............. Date: Sun, 10 Feb 2008 21:37:36 -0500 Randall and Chris, Sorry to be slow in responding to your messages, but you and Chris have given me much to think about and it's going to take a few days more of thinking to digest it all. One open issue that I would like to get pinned down is getting a rough idea of how large these effects are relative to the overall spring forces. I think that Chris had implied that they could be of the same order of magnitude, which I am finding very hard to visualize. Also in his message today I think he was implying that the spring can undergo steplike changes which contain high frequency components. If too large, they could be deadly--see centering discussion below. In particular I am mainly interested in the effects which will occur with the spring under constant tension--not moving significantly. I find that I need to try to separate the fundamental spring-noise issues which will always be present from ones that can be addressed by manufacturing and design techniques such as limiting spring stress, ageing, heat cycling, material choice, etc. For example, I'd heard stories of leaf-spring designs that popped and crackled when they were first assembled and which then, over time, would quiet down to an acceptable noise level. However a noise process that is fundamental and always present would be of greater concern. As an engineer, creep itself does not concern me, so long as it is acceptably slow and not too noisy. Being able to quantify what one might expect to see would be helpful in trying to design something. New subject: Both you and Chris had previously written of the idea of using feedback to help maintain instrument centering. I came up with the following, which if correct has some interesting implications. "The goal of maintaining centering by the use of feedback can be restated as the goal of using feedback to make the instrument insensitive to the unwanted 'noise' forces which would tend to push it off center. When trying to do this, however, a problem unfortunately arises of the 'no free lunch' class, which in fact has nothing directly to do with feedback. The (vertical) instrument simply can't distinguish where an input force is coming from. Is it from the spring getting weaker as the temperature rises, from buoyancy-force changes with the barometer, from spring creep or is it the acceleration-related force from the very low frequency geological signal you wanted to observe? To the extent that you succeed in reducing the instrument's sensitivity to the 'noise' forces you also reduce its sensitivity to the signal force. This can be restated as the well accepted generalization: 'feedback does not affect the signal to noise ratio'. (assuming, of course, that the added feedback components are noise free) However there is one hope. If you can assign F as a frequency below which you will not be looking for signals, you can say that anything changing at rates significantly below F, is noise. This in turn allows you to roll off the instrument sensitivity to forces having frequencies below F and to some extent favor signal over more slowly-varying noise. I am confident that is the reason why commercial instruments aren't designed to have large responses to acceleration/force down to very low frequencies. Instead they are designed to establish a compromise between letting through sufficiently low-frequency seismic signals to be useful, while at the same time resisting the much larger, though more slowly changing, instrument 'noise' forces. That may also explain why so much effort has to go into reducing the noise generators at their source, by using exotic alloys in leaf spring suspensions, maintaining constant (usually low) ambient pressure, and attempting to maintain the temperature as constant as possible, etc." Brett At 09:14 AM 2/10/2008 -0500, you wrote: >Brett, > I've been able now to give enough thought to your comments about > "potholes" to >provide the following response. >Chris 'hit the nail on the head' with his statement "... to cope with >discrete steps in >the zero level". In other words, if the term is at all appropriate, it is >not your >'average' pothole as found in northern climate highways where temperatures >are at times >routinely below freezing. The 'potholes of seismic type' are 'diffusive' >in terms of >both temperature and stress. > There is a paper of mine at http://arxiv.org/html/physics/0307016 >titled "Harmonic oscillator potential to describe internal >dissipation". As discussed >there, the potential function is not fixed. As the seismometer mass moves >back and >forth, Actually in a force-balance instrument the mass does very little moving, which should be an advantage. You are trading physical movement of the spring-mass for electrical 'movement' in the feedback elements. >the equilibrium position, to which it would go if motion were suppressed, >shifts >back and forth. This is the basis for hysteresis--reason the term >'hysteretic damping' >is appropriate. > The problem with this hysteresis is that the mesoanelastic steps > associated with it >are not themselves fixed. Can the amplitude distribution of these steps be predicted? >My study of creep mentioned earlier is proof positive of that >fact. What happens is the strain energy that accumulates at >polycrystalline grain >boundaries causes a rearrangement of the atoms (redistribution of the >defect structures) >when various thresholds are exceeded. Such is the nature of >work-hardening. In primary >creep (exponential variation), the material is trying to arrest the >changes brought about >by the external forcing. 'Success' in so doing results in a conversion to >secondary >(linear variation) creep. If the temperature were zero--end of >story. But temperature >serves to undo the hardening and so a 'balance' results between hardening >and softening. >If the stress levels become large enough, the defect structural >reorganizations become >much bigger, resulting in cracks and eventual fatigue failure. Truly, >what I'm >discussing is one of the most important and yet still mysterious of scientific >phenomena. Its complexity has so far prohibited understanding of the >processes from >first principles. > Randall __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: nature of the mesoscopic nonlinearity From: ChrisAtUpw@....... Date: Sun, 10 Feb 2008 23:45:35 EST In a message dated 11/02/2008, Brett3mr@............. writes: Randall and Chris, Sorry to be slow in responding to your messages, but you and Chris have given me much to think about and it's going to take a few days more of thinking to digest it all. One open issue that I would like to get pinned down is getting a rough idea of how large these effects are relative to the overall spring forces. I think that Chris had implied that they could be of the same order of magnitude, which I am finding very hard to visualize. Hi Brett, You have to make a spring arrangement such that it exactly balances the mass, but has a very slow rate of change of force with position, a few % at most. Hence the somewhat exotic spring arrangements used in seismometers. Also in his message today I think he was implying that the spring can undergo steplike changes which contain high frequency components. If too large, they could be deadly--see centering discussion below. In particular I am mainly interested in the effects which will occur with the spring under constant tension--not moving significantly. Hooke's Law is only an approximation. You get a time dependant component and creep. The creep is noisy and also time dependant. The changes tend to be steps in the characteristic and these decrease with time after the load is applied. New steps may be excited by quakes. The step changes can give problems with velocity feedback circuits - they tend to generate spikes. I find that I need to try to separate the fundamental spring-noise issues which will always be present from ones that can be addressed by manufacturing and design techniques such as limiting spring stress, ageing, heat cycling, material choice, etc. For example, I'd heard stories of leaf-spring designs that popped and crackled when they were first assembled and which then, over time, would quiet down to an acceptable noise level. However a noise process that is fundamental and always present would be of greater concern. All common / practical spring materials are like this. You have the electronic noise, the thermal noise of the sensor itself, the hysteretic noise and the background seismic noise. As an engineer, creep itself does not concern me, so long as it is acceptably slow and not too noisy. Being able to quantify what one might expect to see would be helpful in trying to design something. New subject: Both you and Chris had previously written of the idea of using feedback to help maintain instrument centering. I came up with the following, which if correct has some interesting implications. "The goal of maintaining centering by the use of feedback can be restated as the goal of using feedback to make the instrument insensitive to the unwanted 'noise' forces which would tend to push it off center. When trying to do this, however, a problem unfortunately arises of the 'no free lunch' class, which in fact has nothing directly to do with feedback. The (vertical) instrument simply can't distinguish where an input force is coming from. Is it from the spring getting weaker as the temperature rises, from buoyancy-force changes with the barometer, from spring creep or is it the acceleration-related force from the very low frequency geological signal you wanted to observe? To the extent that you succeed in reducing the instrument's sensitivity to the 'noise' forces you also reduce its sensitivity to the signal force. This can be restated as the well accepted generalization: 'feedback does not affect the signal to noise ratio'. (assuming, of course, that the added feedback components are noise free) Yes you can. You can either re-zero mechanically with a small motor to keep the system in range or use an integrated signal as force feedback. If you integrate the output to say 500 seconds for a 50 second period instrument, you can keep the mean position centred without significantly effecting the 50 second response. This will take out most drifts. With a velocity output, the very long period signals are small. I am confident that is the reason why commercial instruments aren't designed to have large responses to acceleration / force down to very low frequencies. Instead they are designed to establish a compromise between letting through sufficiently low-frequency seismic signals to be useful, while at the same time resisting the much larger, though more slowly changing, instrument 'noise' forces. That may also explain why so much effort has to go into reducing the noise generators at their source, by using exotic alloys in leaf spring suspensions, maintaining constant (usually low) ambient pressure, and attempting to maintain the temperature as constant as possible, etc." See Wielandt's references on psn for feedback seismometer design. Seismometers are usually designed to give a velocity law output directly using quite complicated feedback loops - this is 'traditional'. High sensitivity seismometers usually have periods between 60 and 120 seconds and this covers most surface wave periods of maybe 15 to 40 seconds. A few types go to 360 seconds. To cover all the Earth Eigenmodes, you have to go to about 2,000 seconds. Regards, Chris Chapman
In a message dated 11/02/2008, Brett3mr@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Randall=20 and Chris,

Sorry to be slow in responding to your messages, but you= and=20 Chris have given me much to think about and it's going to take a few days=20= more=20 of thinking to digest it all.

One open issue that I would like to g= et=20 pinned down is getting a rough idea of how large these effects are relativ= e to=20 the overall spring forces.  I think that Chris had implied that they=20 could be of the same order of magnitude, which I am finding very hard to=20 visualize. 
Hi Brett,
 
    You have to make a spring arrangement such that= it=20 exactly balances the mass, but has a very slow rate of change of force with=20 position, a few % at most. Hence the somewhat exotic spring arrangements use= d in=20 seismometers.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Also in=20 his message today I think he was implying that the spring can undergo step= like=20 changes
which contain high frequency components.  If too large, t= hey=20 could be deadly--see centering discussion below.  In particular I am=20 mainly interested in the effects which will occur with the spring under=20 constant tension--not moving significantly.
    Hooke's Law is only an approximation. You get a= =20 time dependant component and creep. The creep is noisy and also time dependa= nt.=20 The changes tend to be steps in the characteristic and these decrease with t= ime=20 after the load is applied. New steps may be excited by quakes. The step chan= ges=20 can give problems with velocity feedback circuits - they tend to generate=20 spikes.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I find=20 that I need to try to separate the fundamental spring-noise issues which w= ill=20 always be present from ones that can be addressed by manufacturing and des= ign=20 techniques such as limiting spring stress, ageing, heat cycling, material=20 choice, etc.  For example, I'd heard stories of leaf-spring designs t= hat=20 popped and crackled when they were first assembled and which then, over ti= me,=20 would quiet down to an acceptable noise level.  However a noise proce= ss=20 that is fundamental and always present would be of greater concern. =20
    All common / practical spring materials are lik= e=20 this. You have the electronic noise, the thermal noise of the sensor itself,= the=20 hysteretic noise and the background seismic noise.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>As an=20 engineer, creep itself does not concern me, so long as it is acceptably sl= ow=20 and not too noisy.  Being able to quantify what one might expect to s= ee=20 would be helpful in trying to design
something.

New subject: Bo= th=20 you and Chris had previously written of the idea of using feedback to help= =20 maintain instrument centering.  I came up with the following, which i= f=20 correct has some interesting implications.

"The goal of maintaining= =20 centering by the use of feedback can be restated as the goal of using feed= back=20 to make the instrument insensitive to the unwanted 'noise' forces which wo= uld=20 tend to push it off center.

When trying to do this, however, a prob= lem=20 unfortunately arises of the 'no free lunch' class, which in fact has nothi= ng=20 directly to do with feedback. The (vertical) instrument simply can't=20 distinguish where an input force is coming from.  Is it from the spri= ng=20 getting weaker as the temperature rises, from buoyancy-force changes with=20= the=20 barometer, from spring creep or is it the acceleration-related force from=20= the=20 very low frequency geological signal you wanted to observe?  To the=20 extent that you succeed in reducing the instrument's sensitivity to the=20 'noise' forces you also reduce its sensitivity to the signal force. =20= This=20 can be restated as the well accepted generalization:  'feedback does=20= not=20 affect the signal to noise ratio'. (assuming, of course, that the added=20 feedback components are noise free)
    Yes you can. You can either re-zero mechanicall= y=20 with a small motor to keep the system in range or use an integrated signal a= s=20 force feedback. If you integrate the output to say 500 seconds for a 50 seco= nd=20 period instrument, you can keep the mean position centred without significan= tly=20 effecting the 50 second response. This will take out most drifts.=20= With=20 a velocity output, the very long period signals are small.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I am=20 confident that is the reason why commercial instruments aren't designed to= =20 have large responses to acceleration / force down to very low=20 frequencies.  Instead they are designed to establish a compromise bet= ween=20 letting through sufficiently low-frequency seismic signals to be useful, w= hile=20 at the same time resisting the much larger, though more slowly changing,=20 instrument 'noise' forces.  That may also explain why so much effort=20= has=20 to go into reducing the noise generators at their source, by using exotic=20 alloys in leaf spring suspensions, maintaining constant
(usually low)=20 ambient pressure, and attempting to maintain the temperature as constant a= s=20 possible, etc."
    See Wielandt's references on psn for=20 feedback seismometer design. Seismometers are usually designed to give=20= a=20 velocity law output directly using quite complicated feedback loops - this i= s=20 'traditional'. High sensitivity seismometers usually have periods between 60= and=20 120 seconds and this covers most surface wave periods of maybe 15 to 40 seco= nds.=20 A few types go to 360 seconds. To cover all the Earth Eigenmodes, you have t= o go=20 to about 2,000 seconds. 
 
    Regards,
 
    Chris Chapman
Subject: Re: Seismograph noise problem From: ChrisAtUpw@....... Date: Mon, 11 Feb 2008 00:01:14 EST In a message dated 10/02/2008, lconklin@............ writes: Thanks for your suggestions. I haven't yet made any serious attempt to work the current manifestation of this problem, mostly for lack of new ideas for something new to try. Hi Larry, You have to approach fault finding step by step. 1 Check the PSU lines for DC level and AC noise first. 2 Visually check all solder joints with a magnifying glass. These are the commonest problems. 3 When the system is noisy, disconnect the oscillator drive, observe any change in the trace and then connect it again. Also measure the DC level on the TP output of the first opamp. 4 Check the two sensors for operation. 5 Assuming that here is no significant change, disconnect the drive again, short the input and observe the output and DC level changes. Try unplugging the sensors in sequence 6 If you can't use a freezer can, try pushing / tapping components with a plastic rod. 7 Definitely check for crevice corrosion under solder joints. 8 Clean and put vaseline on the input plugs. Nickel and particularly chrome plugs develop tough oxide coatings in the damp. 9 You can brush coat the circuit tracks with polyurethane single pack varnish. You can solder through it if necessary. Because you have changed the opamp does not mean that the new opamp is good! When I change opamps, I usually fit a plug in holder. You can wreck an opamp by overheating it during soldering. Regards, Chris Chapman
In a message dated 10/02/2008, lconklin@............ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Thanks=20 for your suggestions.  I haven't yet made any serious attempt to
= work=20 the current manifestation of this problem, mostly for lack of new
idea= s=20 for something new to try.
Hi Larry,
 
    You have to approach fault finding step by=20 step.
 
    1 Check the PSU lines for DC level and AC noise= =20 first.
    2 Visually check all solder joints with a=20 magnifying glass. These are the commonest problems.
    3 When the system is noisy, disconnect the=20 oscillator drive, observe any change in the trace and then connect it again.= =20 Also measure the DC level on the TP output of the first opamp.
    4 Check the two sensors for operation.
    5 Assuming that here is no significant change,=20 disconnect the drive again, short the input and observe the output and DC le= vel=20 changes. Try unplugging the sensors in sequence
    6 If you can't use a freezer can, try pushing /= =20 tapping components with a plastic rod.
    7 Definitely check for crevice corrosion under=20 solder joints.
    8 Clean and put vaseline on the input plugs. Ni= ckel=20 and particularly chrome plugs develop tough oxide coatings in the damp.
    9 You can brush coat the circuit tracks with=20 polyurethane single pack varnish. You can solder through it if necessary.
    
    Because you have changed the opamp does not mea= n=20 that the new opamp is good! When I change opamps, I usually fit a plug in=20 holder. You can wreck an opamp by overheating it during soldering.
 
    Regards,
 
    Chris Chapman
 
Subject: Re: Seismograph noise problem From: ChrisAtUpw@....... Date: Mon, 11 Feb 2008 00:13:31 EST In a message dated 10/02/2008 15:40:02 GMT Standard Time, lconklin@............ writes: One thing that your comments encourage me to revisit is the way the cover over the sensor is made. It is made of 1/4/inch particle board and a little heavy on the heavy side. I is just sitting on the base frame of the sensor, held down by it's own weight. There are soft plastic feet attached where the contact is made to the frame. Hi Larry, You want to make a cover which rests on the floor NOT on the seismometer base. Put a single sheet of bubble wrap over it with the corners folded in. 1/4" particle board won't give much thermal protection. Regards, Chris
In a message dated 10/02/2008 15:40:02 GMT Standard Time,=20 lconklin@............ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>One=20 thing that your comments encourage me to revisit is the way the
cover=20= over=20 the sensor is made.  It is made of 1/4/inch particle board
and a=20 little heavy on the heavy side.  I is just sitting on the base
fr= ame=20 of the sensor, held down by it's own weight.  There are soft
plas= tic=20 feet attached where the contact is made to the=20 frame. 
Hi Larry,
 
    You want to make a cover which rests on the flo= or=20 NOT on the seismometer base. Put a single sheet of bubble wrap over it with=20= the=20 corners folded in. 1/4" particle board won't give much thermal protection.
    Regards,
    Chris
Subject: Re: Geophone From: "Dale Hardy" photon1@........... Date: Mon, 11 Feb 2008 17:25:36 +1100 Hello John, actually there are 2 units, the geophones are from Larry, L15 used ones. One will be on a hillside of conglomerate, 20mtr above sea-level, the other at sea-level on a sand flat. Both have houses nearby. regards Dale ----- Original Message ----- From: "John Lahr" To: Sent: Monday, February 11, 2008 1:02 PM Subject: Re: Geophone > At 05:30 PM 2/10/2008, you wrote: >>Hi, I am going to add a geophone to my station and just would like ideas >>on how best to place one. >>Thanks >>Dale > > Dale, > > Could you provide a few more details about the geophone and your setting? > > John > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of the > message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.20.2 - > Release Date: 10/02/2008 12:00 AM > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Geophone From: John Lahr johnjan@........ Date: Sun, 10 Feb 2008 22:39:35 -0800 Dale, In both cases, could you burry the geophones at least 18-inches deep? Perhaps on the hillside there are some areas with at least that much soil. Should be easy in the sand. John At 10:25 PM 2/10/2008, you wrote: >Hello John, >actually there are 2 units, the geophones are from Larry, L15 used ones. >One will be on a hillside of conglomerate, 20mtr above >sea-level, the other at sea-level on a sand flat. >Both have houses nearby. >regards >Dale > > > > >----- Original Message ----- From: "John Lahr" >To: >Sent: Monday, February 11, 2008 1:02 PM >Subject: Re: Geophone > > >>At 05:30 PM 2/10/2008, you wrote: >>>Hi, I am going to add a geophone to my station and just would like >>>ideas on how best to place one. >>>Thanks >>>Dale >> >>Dale, >> >>Could you provide a few more details about the geophone and your setting? >> >>John >> >>__________________________________________________________ >> >>Public Seismic Network Mailing List (PSN-L) >> >>To leave this list email PSN-L-REQUEST@.............. with the body >>of the message (first line only): unsubscribe >>See http://www.seismicnet.com/maillist.html for more information. >> >> >>-- >>No virus found in this incoming message. >>Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: >>269.20.2 - Release Date: 10/02/2008 12:00 AM >> > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with the body >of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Geophone From: "Dale Hardy" photon1@........... Date: Mon, 11 Feb 2008 17:43:59 +1100 John, yes, burying in either location is not a problem Dale ----- Original Message ----- From: "John Lahr" To: Sent: Monday, February 11, 2008 5:39 PM Subject: Re: Geophone > Dale, > > In both cases, could you burry the geophones at least 18-inches deep? > Perhaps on the hillside > there are some areas with at least that much soil. Should be easy in the > sand. > > John > > At 10:25 PM 2/10/2008, you wrote: >>Hello John, >>actually there are 2 units, the geophones are from Larry, L15 used ones. >>One will be on a hillside of conglomerate, 20mtr above sea-level, the >>other at sea-level on a sand flat. >>Both have houses nearby. >>regards >>Dale __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: nature of the mesoscopic nonlinearity From: Brett Nordgren Brett3mr@............. Date: Mon, 11 Feb 2008 08:17:33 -0500 Chris At 11:45 PM 2/10/2008 -0500, you wrote: >In a message dated 11/02/2008, Brett Nordgren writes: >Hi Brett, > > You have to make a spring arrangement such that it exactly balances > the mass, but has a very slow rate of change of force with position, a > few % at most. Hence the somewhat exotic spring arrangements used in > seismometers. Agreed The example case I've been analyzing uses a 2 sec period. >Hooke's Law is only an approximation. You get a time dependant component >and creep. The creep is noisy and also time dependant. The changes tend to >be steps in the characteristic and these decrease with time after the load >is applied. New steps may be excited by quakes. The step changes can give >problems with velocity feedback circuits - they tend to generate spikes. How noisy? How large steps/spikes? What is their assumed spectrum? > All common / practical spring materials are like this. You have the > electronic noise, the thermal noise of the sensor itself, the hysteretic > noise and the background seismic noise. >When trying to do this, however, a problem unfortunately arises of the 'no >free lunch' class, which in fact has nothing directly to do with feedback. >The (vertical) instrument simply can't distinguish where an input force is >coming from. Is it from the spring getting weaker as the temperature >rises, from buoyancy-force changes with the barometer, from spring creep >or is it the acceleration-related force from the very low frequency >geological signal you wanted to observe? To the extent that you succeed >in reducing the instrument's sensitivity to the 'noise' forces you also >reduce its sensitivity to the signal force. This can be restated as the >well accepted generalization: 'feedback does not affect the signal to >noise ratio'. (assuming, of course, that the added feedback components are >noise free) > Yes you can. You can either re-zero mechanically with a small motor > to keep the system in range or use an integrated signal as force > feedback. If you integrate the output to say 500 seconds for a 50 second > period instrument, you can keep the mean position centred without > significantly effecting the 50 second response. This will take out most > drifts. With a velocity output, the very long period signals are small. That was exactly what I was suggesting; that if you could assign a frequency F below which you didn't want to see data you might be able to do feedback centering. Your example suggests that F is a bit below 1/50sec. What if you wanted to make an instrument which was sensitive to 1/500sec and below. It is only to the degree that you are willing to limit your low-end response that you have a chance of using feedback to perform centering, and then, only if the 'noise' forces are of lower frequency than your signals. To have been properly precise, I should have said '*In any frequency band* feedback does not change the S/N ratio.' Incidentally, the process of mechanical re-zeroing, if automated or done in a systematic way, can be crudely treated as just another very low frequency feedback branch. >I am confident that is the reason why commercial instruments aren't >designed to have large responses to acceleration / force down to very low >frequencies. Instead they are designed to establish a compromise between >letting through sufficiently low-frequency seismic signals to be useful, >while at the same time resisting the much larger, though more slowly >changing, instrument 'noise' forces. That may also explain why so much >effort has to go into reducing the noise generators at their source, by >using exotic alloys in leaf spring suspensions, maintaining constant >(usually low) ambient pressure, and attempting to maintain the temperature >as constant as possible, etc." > See Wielandt's references on psn for feedback seismometer design. > Seismometers are usually designed to give a velocity law output directly > using quite complicated feedback loops - this is 'traditional'. High > sensitivity seismometers usually have periods between 60 and 120 seconds > and this covers most surface wave periods of maybe 15 to 40 seconds. A > few types go to 360 seconds. To cover all the Earth Eigenmodes, you have > to go to about 2,000 seconds. Which again raises the issue; in the 2000 sec instrument, how do you propose to use feedback to maintain centering in the presence of 500sec 'noises'? The very reason for the 60 or 120 or 360 sec limits is to allow the instruments to 'filter out' lower frequency noise. Also the choice of using a response that is flat to velocity, rather than to force/acceleration, is having the significant effect of attenuating the influence of force-noise below the low frequency cutoff. Regards, Brett You can always use my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismograph noise problem From: Roger Sparks rsparks@.......... Date: Mon, 11 Feb 2008 06:35:25 -0800 Hi Larry, The description of your seismometer seems very similar to mine, except for the mount of the sensor cover. I drilled three holes in the concrete floor, then put expansion bolts in. The result is three 1/4 inch bolts extending about 2 inches above the rug. On top of these three bolts I laid a 3/4 inch thick particle board large enough to support the seismometer cover. I stepped on the board both to seat it and to ensure that the supporting bolts were solid. As I recall, I re tightened the bolts after the first step-on, and repeated the procedure. I took the precaution of supporting the seismometer cover with three support points, to prevent rocking of the cover. It sounds like you accomplished the same thing with flexible/soft cover supports. My seismometer goes inside of the cover. I am very satisfied with the mounting now. You can see my occasional postings from Ellensburg, Wash. on the PSN web site. Good luck, Roger > > .------ ------ ------ ------ ------ ------ ------ ------ ------ ------. > | Message 2 | > '------ ------ ------ ------ ------ ------ ------ ------ ------ ------' > Subject: Re: Seismograph noise problem > From: Larry Conklin > Date: Sun, 10 Feb 2008 10:39:43 -0500 > > Hi Roger, > > I it very interesting that you have had a similar problem, and I > appreciate your suggestions. I my case, the sensor in in the basement, > sitting on a concrete floor. Several years ago I epoxied three small > aluminum plates to the floor for the settling screws to sit on. My > concern at the time was that turning the leveling screw against the > concrete was grinding into the floor, leaving concrete dust under the > screw. One of the probable flaws in my construction is that the > leveling screw is very small (#4) and more than likely not really firm > enough. But, when I'm not being "haunted" the thing performs pretty > well. Seems like problems stemming from the mechanical design shouldn't > be episodic the way I have having them. I am using a 3 point mount, and > the other two feet (base of the triangle) are sturdier. > > One thing that your comments encourage me to revisit is the way the > cover over the sensor is made. It is made of 1/4/inch particle board > and a little heavy on the heavy side. I is just sitting on the base > frame of the sensor, held down by it's own weight. There are soft > plastic feet attached where the contact is made to the frame. I don't > normally make a point of pressing everything down to reseat things after > i adjust it. Never occurred to me to do that. One thing I did try > since this last episode started was to put a little piece of tape under > each foot, to introduce a little "sqisshyness" to prevent the kind of > "micro-rocking" that you apparently had. I didn't see any obvious > difference. > > Guess I'm going to have to embark on a real science project. > > Larry > > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: seismometer performance From: Randall Peters PETERS_RD@.......... Date: Mon, 11 Feb 2008 10:26:27 -0500 Confusion about noise limitations of a seismic instrument results largely from misconceptions about how even a perfect instrument behaves. It is universally appreciated that a low natural period is needed, but the nature and the reason for this are not so widely understood. That the sensitivity is proportional to the square of the mechanical period is easy to understand in the case of a simple pendulum. Remember that what excites the pendulum (and every other seismometer) is acceleration. For drive frequencies below the natural period, the angle in radians through which the pendulum gets displaced is a measure of the acceleration. No matter the detector type, its best placement is at the bottom of the pendulum. For a displacement sensor, the output signal is proportional to the acceleration, since the displacement of the bob equals the pendulum length times the measured angle, for angles much less than the 57.3 degrees of a radian (always true). The displacement sensor output is proportional to the length of the pendulum in this case, according to the definition of angle. Further, according to the well known expression for the period of a simple pendulum (two pi times the square root of its length divided by the earth's field, 'little g') we see that the size of the displacement (which determines the sensitivity of the instrument when noise is present) is governed by the square of the period. It can be shown from the mathematics describing every seismometer (by solving its equation of motion derived from Newton's 2nd law) that this is a general result. In other words, every mechanical oscillator configured to behave as a seismometer will be limited in sensitivity according to the square of the natural period. It is important to understand that the instrument's sensitivity to the external excitation is not the only thing to which a seismometer responds. Just as the ideal response involves the square of the period, so the sensitivity of an instrument to its own internal structural changes is likewise proportional to the square of its natural period. It is for this reason (undesirable motions due to internal changes) that virtually all long-period seismometers must use feedback. What feedback is able to accomplish depends on its type. The common commercial force feedback methodology is one in which a very powerful feedback force is employed, using an actuator. The actuator force is tailored to provide the desired 'flat to velocity' output while at the same time providing the desired near critical damping. This synergetic combination of (i) mechanical part and (ii) electronic feedback part -- amounts to something brand new; I will here call it the super-duper-seismometer. For earthquake-only measurements, the force-balance instruments have proven worthy of the title super-seismometer. Nothing else compares favorably with their performance capabilities in the frequency range where they have been fine-tuned to excel. In the frequency range where research is increasingly directed (realm of earth hum and even lower), the super-duper-seismometer has a fatal flaw. Its flat to velocity sensing scheme willl never allow the signals of increasing interest to be seen above noise. There is an alternative feedback scheme that is not thus limited. It is one of 'soft-force feedback' to serve an entirely different function than force-balance. Force-balance 'morphs' a spring into something effectively altogether different--making in effect a 'soft spring having long period' out of a hard spring of astatic type. In the soft-force approach the long period is realized by the time-tested means first used by Lucien LaCoste. As LaCoste discovered in the 1930's, a spring with a period of 20 s is inherently prone to instabilities (through sensitivity to internal structural changes as a key factor, mentioned above). The adverse influences of its imperfections are greatly reduced if the spring is of zero-length. If this zero-length (effectively soft) spring can be gently manipulated so as to stay within an acceptable range of operation, as dictated by the sensor's requirements; then it will be super-sensitive without the noise limitations of the super-duper system. The means to 'manipulate' are not difficult. One way is to continually 'babysit' the instrument and make slight manual tilt adjustments when there is a slow wandering away from the operating point. Of course we all have other things to do, including sleep. But Allan Jones has used a motor/sensor subsystem on some of his horizontal instruments to accomplish this automatically. In my case, I have done the same thing on a vertical by using the original magnet/coil (Faraday law) detector of my Sprengnether vertical--except operating as an actuator instread of a detector. The error signal to accomplish the task is provided by small currents through the coil, their amounts being determined by a long time constant integrator of the output from the displacement sensor with which I modifed the instrument. Incidently, I understand that the very first automated feedback instrument was similar, except hydraulic in nature, using the flow of huge amounts of water to adjust the tilt of the 'pier'. Why is the soft-feedback better? I think on two accounts--the first already mentioned (fatal flaw of velocity sensing). The 2nd involves the nature of the imperfections. It is better to let the spring continually evolve into its "own best' equilibrium, as opposed to strongly manipulating the system with a strong force into the state that is dictated by the feedback network. To use an old expression, it's not good to mess with mother nature. A primary reason that strong-force feedback evolved the way it did is because of the sensor used. It is a capacitive, gap-varying type in which there is virtually no mechanical dynamic range. Thus force balance (almost no inertial mass movement) is necessary if the system is to have any decent sensitivity. By contrast, an area-varying capacitive sensor of the type that I patented can have a large mechanical dynamic range. Thus the mass can be allowed to evolve positionally through small amounts in the manner mentioned above. One other thing I want to mention in closing this discussion. The instrument with strong-force feedback is a 'whole new beast'. It behaves like a non-feedback instrument having a substantially lengthened period. It is not possible by passive electronic means (system without an actuator) to accomplish what is done by means of the electronic feedback forcing. Lowering the corner frequency of the amplifier in a passive system by an amount x does not give rise to the same improvement as lowering the natural mechanical frequency by the same x. The latter gives rise to an x-squared improvement in sensitivity; whereas the former has no chance of being similarly effective--because the electronics must be virtually linear if it is to be acceptable. Randall Subject: Re: Geophone From: ChrisAtUpw@....... Date: Mon, 11 Feb 2008 11:22:35 EST In a message dated 11/02/2008 06:25:56 GMT Standard Time, photon1@........... writes: Hello John, actually there are 2 units, the geophones are from Larry, L15 used ones. One will be on a hillside of conglomerate, 20mtr above sea-level, the other at sea-level on a sand flat. Both have houses nearby. Hi Dale, Check the units for the correct damping resistors. You need about 2.7 K Ohms total for a L15B, allowing for any parallel input resistors on your amplifier board. I aways use metal film resistors. Seal both ends of the 6 core screened connecting cable with silicone rubber to stop it 'breathing'. You will need to seal the top of the units and the cable entry points, if you bury them. You can get an odour free silicone rubber for this. DON'T use the sort which smells strongly of acetic acid - vinegar. You may have to seal the cable entry on the opposite side if they are not in a string. Don't leave any cropped wires exposed. Adhesive Heatshrink and be very useful here and for joining cables.. They should be set level using the spirit level supplied and the arrow should point true North. Alternatively, you could mount them in the bottom of a vertical pipe, but this is more expensive. We can buy an adhesive mastic which never sets called Blu-Tack / White-Tack, from stationers. It is used for attaching paper to notice boards. It is very good for sealing a seismometer case. Regards, Chris Chapman
In a message dated 11/02/2008 06:25:56 GMT Standard Time,=20 photon1@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Hello=20 John,
actually there are 2 units, the geophones are from Larry, L15 use= d=20 ones.
One will be on a hillside of conglomerate, 20mtr above=20 sea-level,  the other
at sea-level on a sand flat.
Both have=20 houses nearby.
Hi Dale,
 
    Check the units for the correct damping resisto= rs.=20 You need about 2.7 K Ohms total for a L15B, allowing for any parallel input=20 resistors on your amplifier board. I aways use metal film resistors.
    Seal both ends of the 6 core screened=20 connecting cable with silicone rubber to stop it 'breathing'.
    You will need to seal the top of the units and=20= the=20 cable entry points, if you bury them. You can get an odour free silicone rub= ber=20 for this. DON'T use the sort which smells strongly of acetic acid - vinegar.= You=20 may have to seal the cable entry on the opposite side if they are not in a=20 string. Don't leave any cropped wires exposed. Adhesive Heatshrink and be ve= ry=20 useful here and for joining cables..
    They should be set level using the spirit level= =20 supplied and the arrow should point true North. 
    Alternatively, you could mount them in the bott= om=20 of a vertical pipe, but this is more expensive.
    We can buy an adhesive mastic which never sets=20 called Blu-Tack / White-Tack, from stationers. It is used for attaching pape= r to=20 notice boards. It is very good for sealing a seismometer case.
 
    Regards,
 
    Chris Chapman
Subject: Re: Seismograph noise problem From: Larry Conklin lconklin@............ Date: Mon, 11 Feb 2008 12:23:56 -0500 Hi Chris, I think I will put your list of suggestions in my "great minds think alike" file. I have tried all of your first 6 suggestions, albeit not since this latest episode started. Regarding corrosion under solder joints, I haven't really checked thoroughly for that yet, but the board looks very clean. Re. your and Roger's comments about the cover, It will take me a little time to build a new one. In the mean time, I think I will try putting some sort of shims under the edges of it so that it is supported by the floor rather than the sensor frame, to see what happens. I already have some cloth wrapped around the base to keep drafts from getting under the cover. One other thing that I'd be interested in hearing your thoughts on is the fact that the "noise" isn't really as random as I'd expect from something like bad solder joints and such. If you look at the data I posted, especially from the LF channel, there definitely seems to be a dominant component with a period of around 20 seconds or so. I've got too many irons in the fire right now to devote full time to debugging this, but I plan to revisit all of your suggestions. Aside with messing with the cover a little, the other very easy test will be to disconnect the oscillator to see what happens. I still have an old test data file from the last time I tried it, and it doesn't look much different from what I saw then with everything hooked up, or now. Larry > Hi Larry, > > You have to approach fault finding step by step. > > 1 Check the PSU lines for DC level and AC noise first. > 2 Visually check all solder joints with a magnifying glass. These > are the commonest problems. > 3 When the system is noisy, disconnect the oscillator drive, observe > any change in the trace and then connect it again. Also measure the DC > level on the TP output of the first opamp. > 4 Check the two sensors for operation. > 5 Assuming that here is no significant change, disconnect the drive > again, short the input and observe the output and DC level changes. Try > unplugging the sensors in sequence > 6 If you can't use a freezer can, try pushing / tapping components > with a plastic rod. > 7 Definitely check for crevice corrosion under solder joints. > 8 Clean and put vaseline on the input plugs. Nickel and particularly > chrome plugs develop tough oxide coatings in the damp. > 9 You can brush coat the circuit tracks with polyurethane single > pack varnish. You can solder through it if necessary. > > Because you have changed the opamp does not mean that the new opamp > is good! When I change opamps, I usually fit a plug in holder. You can > wreck an opamp by overheating it during soldering. > > Regards, > > Chris Chapman > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: seismometer performance From: Brett Nordgren Brett3mr@............. Date: Mon, 11 Feb 2008 13:56:59 -0500 Randall, I just finished the the 3rd major revision and expansion of my overview of seismometer feedback, which may possibly present some of the issues we have been discussing from a slightly different perspective. What I try to do is, without much math, and depending mostly on frequency response graphs, conceptually build up a force-balance instrument, starting with a simple spring-mass. As a test case I use the parameters of Sean-Thomas Morrissey's STM-8, though the approach can be directly applied to any feedback vertical, or even pendulum design. In the process, my goal has been to convey a solid general sense of what feedback can and cannot do when applied to seismic sensors and provide an understanding of how design parameters relate to performance. It is at http://bnordgren.org/seismo/feedback_in_seismic_sensors3.pdf about 2.4MB At 10:26 AM 2/11/2008 -0500, you wrote: >Confusion about noise limitations of a seismic instrument results largely >from misconceptions >about how even a perfect instrument behaves. It is universally >appreciated that a low >natural period is needed, but the nature and the reason for this are not >so widely >understood. >That the sensitivity is proportional to the square of the mechanical period is >easy to understand in the case of a simple pendulum. Remember that what >excites the pendulum >(and every other seismometer) is acceleration. For drive frequencies >below the natural >period, the angle in radians through which the pendulum gets displaced is >a measure of the >acceleration. >No matter the detector type, its best placement is at the bottom of the >pendulum. For a displacement sensor, the output signal is proportional to >the acceleration, >since the displacement of the bob equals the pendulum length times the >measured angle, for >angles much less than the 57.3 degrees of a radian (always true). The >displacement sensor >output is proportional to the length of the pendulum in this case, >according to the >definition of angle. Further, according to the well known expression for >the period of a >simple pendulum (two pi times the square root of its length divided by the >earth's field, >'little g') we see that the size of the displacement (which determines the >sensitivity of the >instrument when noise is present) is governed by the square of the >period. It can be shown >from the mathematics describing every seismometer (by solving its equation >of motion derived >from Newton's 2nd law) that this is a general result. In other words, >every mechanical >oscillator configured to behave as a seismometer will be limited in >sensitivity according to >the square of the natural period. > > It is important to understand that the instrument's sensitivity to > the external >excitation is not the only thing to which a seismometer responds. Just as >the ideal response >involves the square of the period, so the sensitivity of an instrument to >its own internal >structural changes is likewise proportional to the square of its natural >period. It is for >this reason (undesirable motions due to internal changes) that virtually >all long-period >seismometers must use feedback. Completely agree. > What feedback is able to accomplish depends on its type. The common > commercial force >feedback methodology is one in which a very powerful feedback force is >employed, using an >actuator. The actuator force is tailored to provide the desired 'flat to >velocity' output >while at the same time providing the desired near critical damping. This >synergetic >combination of (i) mechanical part and (ii) electronic feedback part -- >amounts to something >brand new; I will here call it the super-duper-seismometer. For >earthquake-only >measurements, the force-balance instruments have proven >worthy of the title super-seismometer. Nothing else compares favorably >with their >performance capabilities in the frequency range where they have been >fine-tuned to excel. > In the frequency range where research is increasingly directed > (realm of earth hum and >even lower), the super-duper-seismometer has a fatal flaw. Its flat to >velocity sensing >scheme willl never allow the signals of increasing interest to be seen >above noise. If by 'noise' you mean internal instrument noise such as from spring imperfections or sensor noise, then it's not clear that extending the instrument's low frequency response will improve the relationship between signals of interest and the instrument noise. Noise arising from places 'deeper' in the circuit may possibly be affected, though. > There >is an alternative feedback scheme that is not thus limited. It is one of >'soft-force >feedback' to serve an entirely different function than >force-balance. Force-balance 'morphs' >a spring into something effectively altogether different--making in effect >a 'soft spring >having long period' out of a hard spring of astatic type. In the >soft-force approach the >long period is realized by the time-tested means first used by Lucien >LaCoste. As LaCoste >discovered in the 1930's, a spring with a period of 20 s is inherently >prone to instabilities >(through sensitivity to internal structural changes as a key factor, >mentioned above). The >adverse influences of its imperfections are greatly reduced if the spring >is of zero-length. >If this zero-length (effectively soft) spring can be gently manipulated so >as to stay within >an acceptable range of operation, as dictated by the sensor's >requirements; then it will be >super-sensitive without the noise limitations of the super-duper >system. The means to >'manipulate' are not difficult. One way is to continually 'babysit' the >instrument and make >slight manual tilt adjustments when there is a slow wandering away from >the operating point. >Of course we all have other things to do, including sleep. But Allan >Jones has used a >motor/sensor subsystem on some of his horizontal instruments to accomplish >this >automatically. In my case, I have done the same thing on a vertical by >using the original >magnet/coil (Faraday law) detector of my Sprengnether vertical--except >operating as an >actuator instread of a detector. The error signal to accomplish the task >is provided by >small currents through the coil, their amounts being determined by a long >time constant >integrator of the output from the displacement sensor with which I modifed >the instrument. >Incidently, I understand that the very first >automated feedback instrument was similar, >except hydraulic in nature, using the flow of huge amounts of water to >adjust the tilt of the >'pier'. What you are describing is indeed feedback. In fact even the systematic manual readjusting of the tilt effects back to zero, say once per hour or even once per day, can be analyzed as a very rough approximation of a linear feedback branch. What threw me was the use of the term 'soft' in describing the process. The process as described corresponds to feedback with very high 'loop gain' which is the usual measure of feedback strength. Your soft feedback is also very strong feedback. What is characteristic, though, of the process is that it is only applied at very low frequencies, presumably lower than any data being collected. > Why is the soft-feedback better? I think on two accounts--the first > already mentioned >(fatal flaw of velocity sensing). The 2nd involves the nature of the >imperfections. It is >better to let the spring continually evolve into its "own best' >equilibrium, as opposed to >strongly manipulating the system with a strong force into the state that >is dictated by the >feedback network. To use an old expression, it's not good to mess with >mother nature. > A primary reason that strong-force feedback evolved the way it did > is because of the >sensor used. It is a capacitive, gap-varying type in which there is >virtually no mechanical >dynamic range. Though which is also quite sensitive and low noise relative to its size. >Thus force balance (almost no inertial mass movement) is necessary if the >system is to have any decent sensitivity. By contrast, an area-varying >capacitive sensor of >the type that I patented can have a large mechanical dynamic range. Thus >the mass can be >allowed to evolve positionally through small amounts in the manner >mentioned above. > One other thing I want to mention in closing this discussion. The > instrument with >strong-force feedback is a 'whole new beast'. It behaves like a >non-feedback instrument >having a substantially lengthened period. It is not possible by passive >electronic means >(system without an actuator) to accomplish what is done by means of the >electronic feedback >forcing. Lowering the corner frequency of the amplifier in a passive >system by an amount x >does not give rise to the same improvement as lowering the natural >mechanical frequency by >the same x. The latter gives rise to an x-squared improvement in >sensitivity; whereas the >former has no chance of being similarly effective--because the electronics >must be virtually >linear if it is to be acceptable. > Randall Brett __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: feedback semantics From: Randall Peters PETERS_RD@.......... Date: Mon, 11 Feb 2008 18:18:31 -0500 Brett, I am not very familiar with the terminology used in the world of engineering controls. My term 'soft' for the feedback scheme that I have used seemed reasonable to me for the following reasons: (i) it is as you noted, happerning at a much lower frequency than most of the signals of interest (say teleseisms at 20 s period, and (ii) it is nowhere near as powerful as the forces required to do force-balance; i.e., keep the mass from ostensibly moving. You mention the matter of using feedback with a pendulum. I can't imagine a reasonably simple pendulum for seismic purposes where feedback would ever be necessary. The primary source of motion at very low frequencies is the change in shape of the earth. Every mass part of our planet contributes to the local field, and so a plumb bob provides information concerning eigenmodes and tides (as the VolksMeter has demonstrated). Your question about my use of the word 'noise' relative to force balance systems--anything that works with the derivative of the position of the inertial mass (flat to velocity sensor) will fail to see earth motions at really long periods (starting around a few thousand seconds or even less). Even though the period of the VolksMeter's simple pendulum is only about 1 s, it is well suited to the study of earth changes happening over days, months, and even years. Randall Subject: Re: Seismograph noise problem From: ChrisAtUpw@....... Date: Mon, 11 Feb 2008 18:53:34 EST In a message dated 11/02/2008, lconklin@............ writes: Regarding corrosion under solder joints, I haven't really checked thoroughly for that yet, but the board looks very clean. Hi Larry, I had a whole Sony TV with crevice corrosion. The joints looked perfect, but you could peel them off a black corrosion coat on the circuit strips. I had to unsolder, clean and resolder every joint on the **** board. Re. your and Roger's comments about the cover, It will take me a little time to build a new one. Putting the cover on the floor isolates the seismometer from pneumatic effects. I use 2" Celotex, but it isn't cheap. Bubble wrap can also be very useful in reducing temperature changes and drafts .... One other thing that I'd be interested in hearing your thoughts on is the fact that the "noise" isn't really as random as I'd expect from something like bad solder joints and such. If you look at the data I posted, especially from the LF channel, there definitely seems to be a dominant component with a period of around 20 seconds or so. I had noted that. It looked as if you were experiencing greatly increased gain, rather than just random noise. This could be resistors, solder joints, diodes or the opamp. Do measure the DC levels on TP. Does the Red/Green LED ever light up? The NE5534 does take about 0.5 micro A to drive it - quite thirsty... Try tapping the components? Unsoldering C49 would isolate everything downstream of the first two opamps. Could there be any strong radio signals at 2 / 4 / 8 / 12 MHz? You do have two radio receivers on the input... Electricity Utility time switches work off radio signals on the power lines. Try connecting an audio amplifier to the circuit before the integrator and listening with headphones? I have solved some noise problems this way. I was getting quite large random pulses which seemed to be real, not instrumental. When I listened, I heard a heavy lorry approaching a sunken drain grating on the corner of the local main road.... I've got too many irons in the fire right now to devote full time to debugging this, but I plan to revisit all of your suggestions. Aside with messing with the cover a little, the other very easy test will be to disconnect the oscillator to see what happens. I still have an old test data file from the last time I tried it, and it doesn't look much different from what I saw then with everything hooked up, or now. I would expect there to be a simple fault which is sensitive to humidity - since heating the board reduced the signal. Good Luck! Regards, Chris Chapman
In a message dated 11/02/2008, lconklin@............ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Regarding corrosion under solder joints, I haven't really checked= =20
thoroughly for that yet, but the board looks very clean.
Hi Larry,
 
    I had a whole Sony TV with crevice=20 corrosion. The joints looked perfect, but you could peel them off a bla= ck=20 corrosion coat on the circuit strips. I had to unsolder, clean and reso= lder=20 every joint on the **** board.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Re. your=20 and Roger's comments about the cover, It will take me a little
time to= =20 build a new one. 
    Putting the cover on the floor isolates the=20 seismometer from pneumatic effects. I use 2" Celotex, but it isn't cheap. Bu= bble=20 wrap can also be very useful in reducing temperature changes and=20 drafts ....
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>One=20 other thing that I'd be interested in hearing your thoughts on is
the=20= fact=20 that the "noise" isn't really as random as I'd expect from
something l= ike=20 bad solder joints and such.  If you look at the data I
posted,=20 especially from the LF channel, there definitely seems to be a
dominan= t=20 component with a period of around 20 seconds or so.
    I had noted that. It looked as if you were=20 experiencing greatly increased gain, rather than just random noise. This cou= ld=20 be resistors, solder joints, diodes or the opamp.
    Do measure the DC levels on TP. Does the Red/Gr= een=20 LED ever light up?
    The NE5534 does take about 0.5 micro A to drive= it=20 - quite thirsty...
    Try tapping the components?
    Unsoldering C49 would isolate everything downst= ream=20 of the first two opamps.
    Could there be any strong radio signals at 2 /=20= 4 /=20 8 / 12 MHz? You do have two radio receivers on the input... Electricity Util= ity=20 time switches work off radio signals on the power lines.
    Try connecting an audio amplifier to the circui= t=20 before the integrator and listening with headphones? I have solved some nois= e=20 problems this way. I was getting quite large random pulses which seemed to b= e=20 real, not instrumental. When I listened, I heard a heavy lorry approaching a= =20 sunken drain grating on the corner of the local main road....
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I've got=20 too many irons in the fire right now to devote full time to debugging this= ,=20 but I plan to revisit all of your suggestions.  Aside with messing wi= th=20 the cover a little, the other very easy test will be
to disconnect the= =20 oscillator to see what happens.  I still have an old test data file f= rom=20 the last time I tried it, and it doesn't look much different from what I s= aw=20 then with everything hooked up, or now.
    I would expect there to be a simple fault which= is=20 sensitive to humidity - since heating the board reduced the signal. Good=20 Luck!
 
    Regards,
 
    Chris Chapman
 
Subject: Re: Seismograph noise problem From: Larry Conklin lconklin@............ Date: Mon, 11 Feb 2008 20:27:39 -0500 Yeah, I've thought about resoldering the entire **** board too, but it's not my first choice of things to try. When I tried to bake out the board under an incandescent lamp that one time, I did seem to get some improvement, but it certainly wasn't very impressive. Regarding the apparent non-randomness of the noise. I had the thought that dampness had gotten into one of the gain pots resulting in a larrge increase in the gain. But, despite the high noise level, I am still able to record quakes and they produce records that are just about the amplitude I would expect. I got a record of the mid-atlantic quake that was good enough that I was able to set the phase picks. Even when the thing is running acceptably, I still notice the same 20 second or so hump spectrum. I do monitor the leveling test point continuously. I put a zero center meter on it so that I better center the leveling. I added a readout of the voltage at the test point to my data logging program. I have a line from the test point connected to a spare channel on my A/D converter. Several of your other suggestions are things I wouldn't have thought of. Tapping in with headphones would be interesting to try in any event. I'm in a residential area not far from a busy street, and I have no doubt that I'm getting a lot of higher frequency noise from traffic and such. I can see a definite dinural variation, quieter at night, noiseier during the day. But I see no variation whatsoever for days on end when the thing is acting up. Interesting. As I have been typing this, the excess noise has diminished very substantially over the span of about 15 minutes, and has stayed pretty low ever since. It would be a sort of Murphy's law in reverse if just when I have been getting motivated to make an all out attack on the problem, it went away spontaneously. Wouldn't be the first time. At any rate, you've given me a lot of food for thought, for which I thank you. Larry ChrisAtUpw@....... wrote: > In a message dated 11/02/2008, lconklin@............ writes: > > Regarding corrosion under solder joints, I haven't really checked > thoroughly for that yet, but the board looks very clean. > > Hi Larry, > > I had a whole Sony TV with crevice corrosion. The joints looked > perfect, but you could peel them off a black corrosion coat on the > circuit strips. I had to unsolder, clean and resolder every joint on the > **** board. > > Re. your and Roger's comments about the cover, It will take me a little > time to build a new one. > > Putting the cover on the floor isolates the seismometer from > pneumatic effects. I use 2" Celotex, but it isn't cheap. Bubble wrap can > also be very useful in reducing temperature changes and drafts .... > > One other thing that I'd be interested in hearing your thoughts on is > the fact that the "noise" isn't really as random as I'd expect from > something like bad solder joints and such. If you look at the data I > posted, especially from the LF channel, there definitely seems to be a > dominant component with a period of around 20 seconds or so. > > I had noted that. It looked as if you were experiencing greatly > increased gain, rather than just random noise. This could be resistors, > solder joints, diodes or the opamp. > Do measure the DC levels on TP. Does the Red/Green LED ever light up? > The NE5534 does take about 0.5 micro A to drive it - quite thirsty... > Try tapping the components? > Unsoldering C49 would isolate everything downstream of the first two > opamps. > Could there be any strong radio signals at 2 / 4 / 8 / 12 MHz? You > do have two radio receivers on the input... Electricity Utility time > switches work off radio signals on the power lines. > Try connecting an audio amplifier to the circuit before the > integrator and listening with headphones? I have solved some noise > problems this way. I was getting quite large random pulses which seemed > to be real, not instrumental. When I listened, I heard a heavy lorry > approaching a sunken drain grating on the corner of the local main road.... > > I've got too many irons in the fire right now to devote full time to > debugging this, but I plan to revisit all of your suggestions. > Aside with messing with the cover a little, the other very easy test > will be > to disconnect the oscillator to see what happens. I still have an > old test data file from the last time I tried it, and it doesn't > look much different from what I saw then with everything hooked up, > or now. > > I would expect there to be a simple fault which is sensitive to > humidity - since heating the board reduced the signal. Good Luck! > > Regards, > > Chris Chapman > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: nature of the mesoscopic nonlinearity From: ChrisAtUpw@....... Date: Mon, 11 Feb 2008 22:43:08 EST In a message dated 11/02/2008, Brett3mr@............. writes: >Hooke's Law is only an approximation. You get a time dependant component >and creep. The creep is noisy and also time dependant. The changes tend to >be steps in the characteristic and these decrease with time after the load >is applied. New steps may be excited by quakes. The step changes can give >problems with velocity feedback circuits - they tend to generate spikes. How noisy? How large steps/spikes? What is their assumed spectrum? Hi Brett, My experience is that the steps can be well above the normal noise level. If they are smaller, they probably don't matter. They are a step function with the appropriate spectrum. The frequency varied greatly from several per second after stressing the spring to an odd one per hour or less after an extended stabilisation period. Springs for seismometers go through extended preparation to reduce / measure the noise. I don't know the full details. > All common / practical spring materials are like this. You have the > electronic noise, including maybe 1/f noise, the thermal noise of the sensor itself, the hysteretic > noise and the background seismic noise. That was exactly what I was suggesting; that if you could assign a frequency F below which you didn't want to see data you might be able to do feedback centering. Your example suggests that F is a bit below 1/50 Hz. What if you wanted to make an instrument which was sensitive to 1/500 Hz and below. It is only to the degree that you are willing to limit your low-end response that you have a chance of using feedback to perform centering, and then, only if the 'noise' forces are of lower frequency than your signals. It is more usual to get very long periods by feedback + integration, maybe numerical? > See Wielandt's references on psn for feedback seismometer design. > Seismometers are usually designed to give a velocity law output directly > using quite complicated feedback loops - this is 'traditional'. High > sensitivity seismometers usually have periods between 60 and 120 seconds > and this covers most surface wave periods of maybe 15 to 40 seconds. A > few types go to 360 seconds. To cover all the Earth Eigenmodes, you have > to go to about 2,000 seconds. Which again raises the issue; in the 2000 sec instrument, how do you propose to use feedback to maintain centering in the presence of 500sec 'noises'? The very reason for the 60 or 120 or 360 sec limits is to allow the instruments to 'filter out' lower frequency noise. Also the choice of using a response that is flat to velocity, rather than to force/acceleration, is having the significant effect of attenuating the influence of force-noise below the low frequency cutoff. Reducing the noise and drift to allow 1000 second responses was what made the Streckeisen STS-1 so difficult to make and so expensive. I would advise using a digital measuring / feedback system to do this for the long periods involved. It is possible to greatly reduce the drift components. By temperature cycling and measuring the result, it is possible to remove a lot of the thermal drift. You hermetically seal the case to keep the gas density constant. With reference to _http://bnordgren.org/seismo/feedback_in_seismic_sensors3.pdf_ (http://bnordgren.org/seismo/feedback_in_seismic_sensors3.pdf) describing feedback systems: >> The difficulty comes when we want to tightly control the frequency response of such a device, or equally important, accurately know its phase response or time delays over the band of frequencies of interest, which is essential to do if its data are to be compared with data from other instruments. Another difficulty comes when we try to maintain the proper centering of the mass in the presence of slow changes in the device or its surroundings. These could arise from changes in temperature, slow changes in ground tilt, earth tides, or in the case of a vertical instrument, spring creep, as well as from numerous other potential sources. In a sensitive instrument such changes could be great enough to move its output completely out of range before mechanical adjustments can be made. Feedback, properly applied, can be used both to shape the instrument response and also to counter some of the effects of slowly-applied errors. Finally, feedback will have the effect of greatly reducing the motion of the mass in response to seismic ground motion. This means that with feedback we might be able to use a displacement transducer which has quite a small range of operation, but which, in return, could be very sensitive. In addition, by limiting the sensor motion we can greatly reduce the effect of transducer and other system nonlinearities. It should be noted that we will be looking here at a feedback system which senses the apparent position of the seismic mass and then feeds back a signal which is used to apply a force to the mass to counter any changes. If we consider a pendulum sensor system, the response is proportional to the square of the period. If you take a 2 second pendulum and reduce the restoring force to give a 20 second system, should you get 100x the response for signals already in the passband? Why should a synthesised feedback response to obtain a longer period result in a much smaller response to the ground motion? You seem to consider that requiring an increased position sensitivity is an advantage. Since we are already at or beyond the easy measurement / stability limit at maybe 10 nm, getting an increased sensitivity / lower instrument noise with a comparable stability is an expensive pain in the backside. There is just no problem in measuring quite large position changes in principle. There are increasing problems in trying to measure smaller changes. If you use a DC path from your position sensor through a long period integrator to the feedback transducer, you can in theory remove ~all position drifts. However, this might require a high current output or a power opamp. You don't need very much gain, but maybe a separate feedback coil? You seem to be adding a high pass filter to the system and then trying to get long period / low drift performance?? A capacitative position sensor system can have a very high linearity. What other system nonlinearities were you considering that could be relevant? See _http://physics.mercer.edu/hpage/peters.html_ (http://physics.mercer.edu/hpage/peters.html) Improving seismometer performance..... Regards, Chris Chapman
In a message dated 11/02/2008, Brett3mr@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>>Hooke's Law is only an approximation. You get a time dependan= t=20 component
>and creep. The creep is noisy and also time dependant. T= he=20 changes tend to
>be steps in the characteristic and these decrease=20= with=20 time after the load
>is applied. New steps may be excited by quakes= ..=20 The step changes can give
>problems with velocity feedback circuits= -=20 they tend to generate spikes.

How noisy?  How large=20 steps/spikes?  What is their assumed spectrum?
Hi Brett,
 
    My experience is that the steps can be wel= l=20 above the normal noise level. If they are smaller, they probably don't matte= r.=20 They are a step function with the appropriate spectrum.
    The frequency varied greatly from several per=20 second after stressing the spring to an odd one per hour or less after an=20 extended stabilisation period. Springs for seismometers go through exte= nded=20 preparation to reduce / measure the noise. I don't know the full=20 details. 
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>>     All common / practical spring materials a= re=20 like this. You have the
> electronic noise, including maybe 1/f noi= se,=20 the thermal noise of the sensor itself, the hysteretic
> noise and=20= the=20 background seismic noise.

That was exactly what I was suggesting; t= hat=20 if you could assign a
frequency F below which you didn't want to see d= ata=20 you might be able to do
feedback centering.  Your example suggest= s=20 that F is a bit below
1/50 Hz.  What if you wanted to make an=20 instrument which was sensitive to
1/500 Hz and below.  It is only= to=20 the degree that you are willing to limit
your low-end response that yo= u=20 have a chance of using feedback to perform
centering, and then, only i= f=20 the 'noise' forces are of lower frequency than
your=20 signals.
    It is more usual to get very long periods by=20 feedback + integration, maybe numerical?
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2> >     See Wielandt's references on psn fo= r=20 feedback seismometer design.
> Seismometers are usually designed to= =20 give a velocity law output directly
> using quite complicated feedb= ack=20 loops - this is 'traditional'. High
> sensitivity seismometers usua= lly=20 have periods between 60 and 120 seconds
> and this covers most surf= ace=20 wave periods of maybe 15 to 40 seconds. A
> few types go to 360=20 seconds. To cover all the Earth Eigenmodes, you have
> to go to abo= ut=20 2,000 seconds.

Which again raises the issue; in the 2000 sec=20 instrument, how do you
propose to use feedback to maintain centering i= n=20 the presence of 500sec
'noises'?  The very reason for the 60 or 1= 20=20 or 360 sec limits is to allow
the instruments to 'filter out' lower=20 frequency noise.  Also the choice of
using a response that is fla= t to=20 velocity, rather than to
force/acceleration, is having the significant= =20 effect of attenuating the
influence of force-noise below the low frequ= ency=20 cutoff.
    Reducing the noise and drift to allow 1000= =20 second responses was what made the Streckeisen STS-1 so difficult to ma= ke=20 and so expensive. I would advise using a digital measuring / feedback system= to=20 do this for the long periods involved. It is possible to greatly reduce the=20 drift components. By temperature cycling and measuring the result, it i= s=20 possible to remove a lot of the thermal drift. You hermetically seal the cas= e to=20 keep the gas density constant. 
 
     With reference to http:/= /bnordgren.org/seismo/feedback_in_seismic_sensors3.pdf =20 describing feedback systems:
 
>>    The difficulty comes when we want to=20 tightly control the frequency response of such a device, or
equally=20 important, accurately know its phase response or time delays over the band o= f=20 frequencies of
interest, which is essential to do if its data are to be=20 compared with data from other instruments.
Another difficulty comes when=20= we=20 try to maintain the proper centering of the mass in the presence of
slow=20 changes in the device or its surroundings. These could arise from changes in= =20 temperature, slow
changes in ground tilt, earth tides, or in the case of=20= a=20 vertical instrument, spring creep, as well as from
numerous other potenti= al=20 sources. In a sensitive instrument such changes could be great enough to
= move=20 its output completely out of range before mechanical adjustments can be made= ..=20 Feedback,
properly applied, can be used both to shape the instrument resp= onse=20 and also to counter some of the
effects of slowly-applied errors. Finally= ,=20 feedback will have the effect of greatly reducing the motion
of the mass=20= in=20 response to seismic ground motion. This means that with feedback we might be= =20 able to
use a displacement transducer which has quite a small range of=20 operation, but which, in return, could
be very sensitive. In addition, by= =20 limiting the sensor motion we can greatly reduce the effect of
transducer= and=20 other system nonlinearities. It should be noted that we will be looking here= at=20 a
feedback system which senses the apparent position of the seismic mass=20= and=20 then feeds back a signal
which is used to apply a force to the mass to=20 counter any changes.
 
    If we consider a pendulum sensor system, the=20 response is proportional to the square of the period. If you take a 2 second= =20 pendulum and reduce the restoring force to give a 20 second system, should y= ou=20 get 100x the response for signals already in the passband?
 
    Why should a synthesised feedback=20 response to obtain a longer period result in a much smaller respon= se=20 to the ground motion?
 
    You seem to consider that requiring an increase= d=20 position sensitivity is an advantage. Since we are already at or beyond = ;the=20 easy measurement / stability limit at maybe 10 nm, getting an increased= =20 sensitivity / lower instrument noise with a comparable stability is an=20 expensive pain in the backside. There is just no problem in measuring q= uite=20 large position changes in principle. There are increasing problems in trying= to=20 measure smaller changes.
 
   If you use a DC path from your position sensor throug= h a=20 long period integrator to the feedback transducer, you can in=20 theory remove ~all position drifts. However, this might require a high=20 current output or a power opamp. You don't need very much gain, but maybe a=20 separate feedback coil?
 
    You seem to be adding a high pass filter to the= =20 system and then