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@............
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
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
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 -----

From:

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>

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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 =
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

--

<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
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
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
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
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
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
(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
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
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
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
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 ----- =

From:

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

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
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
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
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.

&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
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.

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
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

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
=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 _________________________________________________________________________= ___________
http://www.yahoo.com/r/hs
_____= _____________________________________________________

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
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
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
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

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
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
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
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
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

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 trying to get long period / low drift performance??

A capacitative position sensor system can have=20= a=20 very high linearity. What other system nonlinearities were you considering t= hat=20 could be relevant?

See http://physics.mercer.e= du/hpage/peters.html Improving=20 seismometer performance.....

Regards,

Chris Chapman
Subject: BAJA CALIFORNIA, MEXICO Aftershocks From: "Jerry Payton" gpayton880@....... Date: Tue, 12 Feb 2008 14:24:53 -0600 Forgive me for asking, but it normal to have so many after shocks after a 5.4 EQ such as BAJA CALIFORNIA, MEXICO has had since the 9th?
Forgive me for asking, but it normal to have so many after shocks = after a=20 5.4 EQ such as BAJA CALIFORNIA, MEXICO has had since the=20 9th?
Subject: Re: BAJA CALIFORNIA, MEXICO Aftershocks From: Bob Hancock carpediem1@......... Date: Tue, 12 Feb 2008 17:15:24 -0700 Jerry - The problem is the ability to see all of the aftershocks normally generated by a seismic event. On the header of the site most of us use to view various events world wide, it states: Latest Earthquakes Magnitude 2.5 or Greater in the United States and Adjacent Areas and Magnitude 4.0 or Greater in the Rest of the World - Last 7 days You can see events down to M 2.5 on this list because the Baja events were adjacent to Southern California. If you go to the map of California and Nevada that shows recent event, and then click on one pf the squares that show the recent Baja events, you will find the following link near the bottom of the page: List of Earthquakes on this Map (with MAP) This link will give you a much more complete list of events, some even less that M 1.0 The variable is having access to the information on all the aftershocks. Bob Hancock On 2/12/08 1:24 PM, "Jerry Payton" wrote: > Forgive me for asking, but it normal to have so many after shocks after a 5.4 > EQ such as BAJA CALIFORNIA, MEXICO has had since the 9th? > Re: BAJA CALIFORNIA, MEXICO Aftershocks Jerry= -

The problem is the ability to see all of the aftershocks normally generated= by a seismic event.  On the header of the site most of us use to view = various events world wide, it states:

Latest Earthquakes Magnitude 2.5 or Greater in the United States and = Adjacent Areas and Magnitude 4.0 or Greater in the Rest of the World - Last = 7 days

You can see events down to M 2.5 on this list because the Baja events were = adjacent to Southern California.  If you go to the map of California an= d Nevada that shows recent event, and then click on one pf the squares that = show the recent Baja events, you will find the following link near the botto= m of the page:

List of Earthquakes on this Map (with MAP)

This link will give you a much more complete list of events, some even less= that M 1.0

The variable is having access to the information on all the aftershocks.
Bob Hancock

On 2/12/08 1:24 PM, "Jerry Payton" <gpayton880@.......> wro= te:

Forgive me for asking, but it normal to have so many af= ter shocks after a 5.4 EQ such as BAJA CALIFORNIA, MEXICO has had since the = 9th?

Thank you, Bob.  Yes, I have seen that other URL, but = not in this=20 case.  I was just amazed by the number listed, as you say, above = 2.5. =20 Even the ANDREANOF ISLANDS, ALEUTIAN IS., ALASKA complex does not seem = to have=20 this many.

As usual, I was just curious!

Best regards,
Jerry

----- Original Message -----=20
From: Bob = Hancock=20
Sent: Tuesday, February 12, 2008 6:15 PM
Subject: Re: BAJA CALIFORNIA, MEXICO Aftershocks

Jerry -

The problem is the ability to = see all of=20 the aftershocks normally generated by a seismic event.  On the = header of=20 the site most of us use to view various events world wide, it=20 states:

Latest Earthquakes Magnitude 2.5 or Greater = in the=20 United States and Adjacent Areas and Magnitude 4.0 or Greater in the = Rest of the=20 World - Last 7 days

You can see=20 events down to M 2.5 on this list because the Baja events were adjacent = to=20 Southern California.  If you go to the map of California and Nevada = that=20 shows recent event, and then click on one pf the squares that show the = recent=20 Baja events, you will find the following link near the bottom of the=20 page:

List of Earthquakes on this Map (with=20 MAP)

This link will give you a much more = complete list of=20 events, some even less that M 1.0

The variable is having access = to the=20 information on all the aftershocks.

Bob = Hancock

On=20 2/12/08 1:24 PM, "Jerry Payton" <gpayton880@.......>=20 wrote:

Forgive me for asking, but it normal to have = so many=20 after shocks after a 5.4 EQ such as BAJA CALIFORNIA, MEXICO has had = since the=20 9th?

>     It= is more usual to get very long periods by feedback + integration,
> maybe numerical?

If you are speaking of integral feedback, it *reduces* the low frequency response and somewhat raises the low frequency rolloff frequency, hence
shortening the 'period' slightly, though one can't really talk of a
'period' when you are describing something more complex than a simple
resonant device, i.e. one which has multiple poles in its transfer
function.  In the STM-8 adding the integral branch raises the low frequ= ency
rolloff you get from using derivative feedback alone, from 0.007 Hz to
0.011 Hz, which you can see in the 'FISS' paper.  However, it is the derivative feedback which effectively improves the low frequency response, <= BR> by flattening and widening the velocity response curve.  In a real sens= e,
it improves both low frequency and high frequency responses.

Numerical integration looks interesting.  What I think I need to make i= t
work is a D/A with something like 24-bit resolution and correspondingly low=20=
noise.  Haven't looked too hard, and haven't found any.

My understanding was that the 3= 60 second low-end response of the STS-1 was
about as good as you can get, while still maintaining instrument noise
below earth noise, and it required using every possible scheme to reduce and slow internal noise sources.

The STS-2 goes to this. Particular ver= sions of the STS-1 would go out to 1,000 seconds. It is a very hard way to g= et this performance!

That also raises the interestin= g question, whether some of that 'low earth
noise' isn't exactly what you are looking to measure.

There is a lot of earth noise down to=20= the Eigenmodes, which are interesting in themselves. Transient signals occur= which look very like quake precursors.

>     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?

Not sure how you are proposing to reduce the restoring force.  If you a= re
suggesting feedback, it actually doesn't act in that way.

Positive feedback does and it will reduce the period.

It effectively
applies a very large velocity-damping force on=20= the pendulum in a very linear manner.  The result is that the low frequ= ency corner is lower and
the high frequency corner is higher than the original single peak at 2
seconds.  In a sense the system is still acting as a 2 second pendulum=20= but
one which is extremely overdamped. see 'FISS'

>      Why should a synthesised feedback respons= e to obtain a longer period
> result in a much smaller response to the ground motion?

The simple answer: Because (negative) feedback always acts to lower the
instrument sensitivity to position, velocity and acceleration, (excepting in a few pathological cases).  A complete answer involves actually doin= g
the computations for a particular case and examining the results such as is=20=
done in 'FISS'.

>      You seem to consider that requiring an in= creased position

Don't know about *requiring* greater sensitivity, but obtaining greater
sensitivity allows for better signal/noise where the noise is that which arises in the measurement circuitry and its connections, the C/D converter,=20=
for example.  In general improving s/n should allow expanding the
performance envelope.

>Since we are already at or beyond the easy measurement / stability limit=
>at maybe 10 nm, getting an increased sensitivity / lower instrument nois= e
>with a comparable stability is an expensive pain in the backside. There=20= is
>just no problem in measuring quite large position changes in principle.=20=
>There are increasing problems in trying to measure smaller changes.

Not exactly following here.  Can you try this from a different
angle.  Incidentally, I often use the terms 'stability' and 'noise' to=20=
describe inverse aspects of the same thing.

You are using a position sensor, which= will have a measurement range and a  noise level which limits what you= can sense. I am enquiring what resolution you can get. The practical limit=20= is likely to be set above this by thermal varriations.

>     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.

Yes, but when you call it a long-period integrator you imply that there is <= BR> no DC path.  It only integrates down to the frequency corresponding to=20= the
'long period'.  An integrator which integrates down to DC would be have= to
be called an 'infinite' period integrator.  In practice 10,000 seconds=20= or
somewhat longer might be possible with a very good capacitor.  Anyone f= or
digital?  Also, position drifts which occur more rapidly than DC (which= I
trust includes most of them:-) are only partially cancelled by integration <= BR> depending on their frequency content.  The slower they are, the more th= ey
are cancelled.

No. They can go down to DC. Randal use= s one on his Sprengnether. See my reference. You have a large resistance ont= o the negative input of a FET opamp and a capacitor (+ resistor?) in the fee= dback loop.

>    &nb= sp; You seem to be adding a high pass filter to the system and then
> trying to get long period / low drift performance??

If you are talking about adding a 0.002Hz high-pass filter to the output to=20=
camouflage drift, it works, but I don't believe that's the best
approach.  However I was analyzing the STM-8 which uses that.  A b= etter
solution might be with 'better' feedback.

>      A capacitative position sensor system can= have a very high
> linearity. What other system nonlinearities were you considering that <= BR> > could be relevant?

Primarily the position sensor system.  That would include, of course,&n= bsp; the
C/D converter as well as the capacitor.  When you say very high lineari= ty
are you implying 1%, 0.1%, 0.01%....?  Have any measurements been made?=

My guesstimate would be in the 0.1% region, probably bett= er. It will depend mostly on the precision of the physical sensor constructi= on. The linearity over a small range will be extreme.

My
concern is that even with fairly small nonlinearity, large amplitu= de,
higher frequency signals can mix to generate small low-frequency difference=20=
signals which could possibly confound measurements attempted down at very low frequencies.  Only with specific linearity figures could one rule <= BR> in/out that effect by calculating its magnitude.  Also the spring in a=20=
vertical, or pendulum geometry might possibly add nonlinearity.

I would not expect even moderate quakes= to generate serious non linearity. You are more likely to run out of detect= or range. The angles are less than 2 degrees.

Regards,

Chris
Subject: How much mass ? From: jonfr@......... Date: Wed, 13 Feb 2008 15:49:50 -0500 (EST) Hi all I am continuing to planning the build of an lechman sensor. But I am wondering what the ideal mass is going to have to be. But I am hoping for at as many seconds as I can. Preferably around 20 seconds. But only if I can. Regards. Jón Frímann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: How much mass ? From: ChrisAtUpw@....... Date: Wed, 13 Feb 2008 22:07:36 EST In a message dated 2008/02/13, jonfr@......... writes: > Hi all > I am continuing to planning the build of an Lehman sensor. But I am > wondering what the ideal mass is going to have to be. But I am hoping for > at as many seconds as I can. Preferably around 20 seconds.=20 Hi Jon, The mass is not important in a Lehman, only the length between the=20 hinge and the centre of mass =3D L ~56 cm. You need to keep the arm rigid bu= t=20 light. Between 1/2 and 1 kg is about right, certainly no more. We use brass=20= rod. I=20 use 3" x 1" Aluminum U channel, 1/8" Al plate and SS bolts. The magnets are=20 NdFeB, 1" square x 1/8" thick for the sensor and 1" x 1/2" x 1/4" thick for=20= the=20 damper, 4 off each type Have a look at our Lehman school seismometer. The dimensions and=20 construction are shown. Don't use any of the constructions shown on psn. See= =20 http://www.bgs.ac.uk/education/school_seismology/seismometer.html I don't suppose that you are feeling rich, but MUTR sell them for=20= =A3290=20 + carriage. ~IK 33,282 + carriage. I don't know about your import duty or tax. This=20 includes the sensor, the electronics and the PSU. It plugs into a PC compute= r and=20 runs under AmaSeis. You can get 30 seconds, although they only claim 20. Let me know if you need more information. Regards, Chris Chapman =20 In a me= ssage dated 2008/02/13, jonfr@......... writes:

Hi all
I am continuing to planning the build of an Lehman sensor. But I am
wondering what the ideal mass is going to have to be. But I am hoping for at as many seconds as I can. Preferably around 20 seconds.

Hi Jon,

The mass is not important in a Lehman,=20= only the length between the hinge and the centre of mass =3D L ~56 cm. You n= eed to keep the arm rigid but light. Between 1/2 and 1 kg is about right, ce= rtainly no more. We use brass rod. I use 3" x 1" Aluminum U channel, 1/8" Al= plate and SS bolts. The magnets are NdFeB, 1" square x 1/8" thick for the s= ensor and 1" x 1/2" x 1/4" thick for the damper, 4 off each type

Have a look at our Lehman school seismo= meter. The dimensions and construction are shown. Don't use any of the const= ructions shown on psn. See http://www.bgs.ac.uk/education/school_seismology/= seismometer.html
I don't suppose that you are feeling ri= ch, but MUTR sell them for =A3290 + carriage.
~IK 33,282 + carriage. I don't know about your import duty or tax. This incl= udes the sensor, the electronics and the PSU. It plugs into a PC computer an= d runs under AmaSeis. You can get 30 seconds, although they only claim 20.

Regards,

Chris Chapman
Subject: RE: How much mass ? From: "Steve Hammond" shammon1@............. Date: Thu, 14 Feb 2008 00:29:57 -0800 Hi, Jon, I like to use the old style Lehman design. The device I built = with the best results was the PSN San Jose Lehmans which used a 1-in square aluminum rod L=3D 80cm and 80-ounce lead mass. They had a natural period = of 20-seconds with minimal setup effort. The total boom length was 100cm = and they used a brass plate mounted at the end of the boom for the damping. = I was very happy with the performance. One of the issues you will face is = the selection of the gauge of the upper support wire. I tried to use #8 = machine (piano) wire but it kept breaking during use. I increased the wire gauge = to #10 machine wire and the wire life was about 1-year before rust causes = the wire to snap under tension.=20 =20 When I moved here to Aptos, California I was forced to reduce the length = of the boom to L=3D60cm because of limited space as seen in the photos in = the link below and the resulting natural period is now typically 10-12 = seconds. Needless to say, the performance these Lehmans are marginal and I live = near the ocean and the wave action causes them to osculate during storms. = When I have the time I'm going to pull them out and build one L=3D80cm device.=20 =20 My suggestion is to use the calculation seen on this list (sorry I don't have the calculation for a natural period of a garden gate Lehman at = hand. Maybe somebody on the list does??) to determine the boom length you = desire. Then plan the design based on that calculation. You said you wanted a = device with a period of 20-second and as pointed out below by Chris, L is based = on the length of the boom measured from the pivot point to the center of = the mass weight (Chris, do you have this calculation??). I have found that setting the device up this way also reduces the impact of ground = deformation (boom does not remains level and centered) over time which improves the overall operation of the device keeping the boom off the stops.=20 http://pw2.netcom.com/~shammon1/AptosStn.htm =20 =20 Regards, Steve Hammond Aptos California, PSN San Jose. =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of ChrisAtUpw@....... Sent: Wednesday, February 13, 2008 7:08 PM To: psn-l@.............. Subject: Re: How much mass ? In a message dated 2008/02/13, jonfr@......... writes: Hi all I am continuing to planning the build of an Lehman sensor. But I am wondering what the ideal mass is going to have to be. But I am hoping = for at as many seconds as I can. Preferably around 20 seconds.=20 Hi Jon, The mass is not important in a Lehman, only the length between = the hinge and the centre of mass =3D L ~56 cm. You need to keep the arm = rigid but light. Between 1/2 and 1 kg is about right, certainly no more. We use = brass rod. I use 3" x 1" Aluminum U channel, 1/8" Al plate and SS bolts. The magnets are NdFeB, 1" square x 1/8" thick for the sensor and 1" x 1/2" x 1/4" thick for the damper, 4 off each type Have a look at our Lehman school seismometer. The dimensions and construction are shown. Don't use any of the constructions shown on psn. = See http://www.bgs.ac.uk/education/school_seismology/seismometer.html I don't suppose that you are feeling rich, but MUTR sell them for =A3290 + carriage. ~IK 33,282 + carriage. I don't know about your import duty or tax. This includes the sensor, the electronics and the PSU. It plugs into a PC computer and runs under AmaSeis. You can get 30 seconds, although they = only claim 20. Let me know if you need more information. Regards, Chris Chapman=20 Message
Hi,=20 Jon, I like to use the old style Lehman design. The device I built = with the=20 best results was the PSN San Jose Lehmans which used a 1-in square = aluminum=20 rod L=3D 80cm and 80-ounce lead mass. They had a natural = period of=20 20-seconds with minimal setup effort. The total boom length was 100cm=20 and they used a brass plate mounted at the end of the = boom for=20 the damping. I was very happy with the performance. One of the issues = you will=20 face is the selection of the gauge of the upper support wire. = I tried to=20 use #8 machine (piano) wire but it kept breaking during use. I increased = the=20 wire gauge to #10 machine wire and the wire life was about = 1-year=20 before rust causes the wire to snap under = tension.

When I=20 moved here to Aptos, California I was forced to reduce the length of the = boom to=20 L=3D60cm because of limited space as seen in the photos in the link = below and the=20 resulting natural period is now typically 10-12 seconds. Needless to = say, the=20 performance these Lehmans are marginal and I live near the = ocean and=20 the wave action causes them to osculate during storms. When I have the = time I'm=20 going to pull them out and build one L=3D80cm device. =

My=20 suggestion is to use the calculation seen on this list (sorry I don't = have the=20 calculation for a natural period of a garden gate Lehman at hand. = Maybe=20 somebody on the list does??) to determine the boom length you desire. = Then plan=20 the design based on that calculation. You said you wanted a device with = a period=20 of 20-second and as pointed out below by Chris, L is based on the length = of the=20 boom measured from the pivot point to the center of the mass weight = (Chris, do=20 you have this calculation??). I have found that setting the device = up this=20 way also reduces the impact of ground deformation (boom does not=20 remains level and centered) over time which improves the overall = operation=20 of the device keeping the boom off the stops.
http://pw2.netcom.c= om/~shammon1/AptosStn.htm

Regards, Steve Hammond Aptos California,  PSN San=20 Jose.

-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@............... On Behalf Of=20 ChrisAtUpw@.......
Sent: Wednesday, February 13, 2008 7:08 = PM
To: psn-l@..............
Subject: Re: How much = mass=20 ?

In a message dated 2008/02/13, jonfr@......... = writes:

Hi all
I am continuing to planning the build of an = Lehman=20 sensor. But I am
wondering what the ideal mass is going to have = to be.=20 But I am hoping for
at as many seconds as I can. Preferably = around 20=20 seconds.

Hi=20 Jon,

The mass is not = important in=20 a Lehman, only the length between the hinge and the centre of mass =3D = L ~56 cm.=20 You need to keep the arm rigid but light. Between 1/2 and 1 kg is = about right,=20 certainly no more. We use brass rod. I use 3" x 1" Aluminum U channel, = 1/8" Al=20 plate and SS bolts. The magnets are NdFeB, 1" square x 1/8" thick for = the=20 sensor and 1" x 1/2" x 1/4" thick for the damper, 4 off each=20 type

Have a look at our = Lehman=20 school seismometer. The dimensions and construction are shown. Don't = use any=20 of the constructions shown on psn. See=20 = http://www.bgs.ac.uk/education/school_seismology/seismometer.html
&nbs= p;     =20 I don't suppose that you are feeling rich, but MUTR sell them for = =A3290 +=20 carriage.
~IK 33,282 + carriage. I don't know about your import = duty or=20 tax. This includes the sensor, the electronics and the PSU. It plugs = into a PC=20 computer and runs under AmaSeis. You can get 30 seconds, although they = only=20 claim 20.

=20 Regards,

Chris = Chapman
=20

Hi, Jon, I like to use the old= style Lehman design. The device I built with the best results was the PSN S= an Jose Lehmans which used a 1-in square aluminum rod L=3D 80cm and 80-ounce= lead mass. They had a natural period of 20-seconds with minimal setup effor= t. The total boom length was 100cm and they used a brass plate mounted at th= e end of the boom for the damping. I was very happy with the performance. On= e of the issues you will face is the selection of the gauge of the upper sup= port wire. I tried to use #8 machine (piano) wire but it kept breaking durin= g use. I increased the wire gauge to #10 machine wire and the wire life was=20= about 1-year before rust causes the wire to snap under tension.

Hi Steve,

If you use D'Addario piano wire, it com= es protected with Nickel plating.
Use either Aluminum or Copper plate for= the damper. Al works, but 1/16" Cu is better.
I use 1" square x 1/8" thick NdFeB magn= ets for the sensor and 1" x 1/2" x 1/4" thick NdFeB magnets for the damper,=20= four off in both cases. A N/S pair on one 1/4" backing plate faces a S/N pai= r on the other backing plate. The backing plates are held in position by 1/4= " zinc plated mild steel bolts. This greatly reduces any stray field.
Put the coil on the arm and the magnet=20= on the base. If you put a magnet on the arm, you will pick up a lot of magne= tic noise from the house wiring, passing trains and lorries etc.

When I moved here to Aptos, Ca= lifornia I was forced to reduce the length of the boom to L=3D60cm because o= f limited space as seen in the photos in the link below and the resulting na= tural period is now typically 10-12 seconds. Needless to say, the performanc= e these Lehmans are marginal and I live near the ocean and the wave action c= auses them to osculate during storms.

You should be able to get 30 seconds o= ut of a 60 cm arm quite OK. Most period limitations are caused by a poor low= er suspension, such as a point in a cup or knife edge. It improves the perio= d if you put the mass at the end of the arm.
Use 3/4" square or round Al tube for th= e arm - definitely not solid. You want to keep the arm light but rigid compa= red to the mass. I use 15 mm SS water pipe + plumbing fittings
The bottom hinge should be ball on a pl= ane or crossed cylinder. You put the SS ball on the upright and the SS / WC=20= plane / SS blade the end of the arm. For WC rod, you can use 1/8" Tungsten C= arbide drill shanks, with the vertical on the upright. See www.smallparts.co= m. You can also buy type 416 SS 1/4" shoulder bolts from McMaster Carr. www.= mcmaster.com
If you construct a double T frame simil= ar to http://www.bgs.ac.uk/education/school_seismology/seismometer.html you=20= can set up the system and then trim the response - all adjustments are seque= ntial, not inter related like on the psn designs. This makes setup and adjus= tment far easier. The red block is a support, with a horizontal damping blad= e and the sliding damping magnet is placed on the bottom frame. The coil is=20= fixed to the outside end and swings between the other magnet block. The diag= onal Al support tube prevents rotation.
I used 3" x 1" Al U Channel with triang= ular 6" x 6" x 1/8" Al plates to support the joint in the prototype. This is= easy to make and to set up. I use 1/4" SS bolts.

My suggestion is to use the c= alculation seen on this list to determine the boom length you desire. Then p= lan the design based on that calculation. You said you wanted a device with=20= a period of 20-second and as pointed out below by Chris, L is based on the l= ength of the boom measured from the pivot point to the center of the mass we= ight (Chris, do you have this calculation?). I have found that setting the d= evice up this way also reduces the impact of ground deformation (boom does n= ot remains level and centered) over time which improves the overall operatio= n of the device keeping the boom off the stops.
http://pw2.netcom.= com/~shammon1/AptosStn.htm

If the distance between the hinge and=20= the centre of mass is L metres and the suspension angle is A, the period T=20= =3D 2xPixSqrt(L / (9.81 x sin(A))) I use 0.56 m which would give a 1.5 sec p= endulum if held vertically. A is ~1/3 degree.
Alnico magnets are now quite expensive.= NdFeB magnets are much cheaper and give a much higher output. For damper an= d coil designs - click on Lehman at http://jclahr.com/science/psn/chapman/ M= ake the damping blade wide so that it covers both magnets at all times as sh= own.
There is also an alternative design und= er muventures.
The boom does not have to be level, but= it should be adjusted parallel with the lower frame. Then you can simply sl= ide the damping magnet further over the horizontal damping blade to adjust t= he damping.
You adjust the whole rigid frame to cen= tre the arm and to set the period. I use three SS plates glued to the concre= te floor for the screw adjusters. I glued SS bearings into the end of the ad= just bolts. Then they don't move about / wander when you adjust them. The SS= mounting nuts are glued to the underside of the frame.

Regards,

=

-----Original = Message-----
From: = psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of ChrisAtUpw@.......
Sent: =
Thursday, February 14, = 2008 6:49 AM
To: = psn-l@..............
Subject: Re: How much = mass ?

In a message dated = 2008/02/14, shammon1@............. writes:
See comment = below:

= Hi, Jon, I like to use the old style Lehman design. The device I built with the = best results was the PSN San Jose Lehmans which used a 1-in square aluminum = rod L=3D 80cm and 80-ounce lead mass. They had a natural period of 20-seconds = with minimal setup effort. The total boom length was 100cm and they used a = brass plate mounted at the end of the boom for the damping. I was very happy = with the performance. One of the issues you will face is the selection of the = gauge of the upper support wire. I tried to use #8 machine (piano) wire but it = kept breaking during use. I increased the wire gauge to #10 machine wire and = the wire life was about 1-year before rust causes the wire to snap under = tension.

=

Hi Steve,

If you use D'Addario piano wire, it = comes protected with Nickel plating.
Use either Aluminum or Copper plate = for the damper. Al works, but 1/16" Cu is better.
I use 1" square x 1/8" = thick NdFeB magnets for the sensor and 1" x 1/2" x 1/4" thick = NdFeB magnets for the damper, four off in both cases. A N/S pair on one = 1/4" backing plate faces a S/N pair on the other backing plate. The backing = plates are held in position by 1/4" zinc plated mild steel bolts. This = greatly reduces any stray field.
Put the coil on the arm and the = magnet on the base. If you put a magnet on the arm, you will pick up a lot of = magnetic noise from the house wiring, passing trains and lorries etc.

Update = = 2/14/08: Thanks Chris, I’ll try mounting the = coil on the boom in the next revision. I never wanted to deal with the lead = wires off the rear of the boom. Do you have any tips for frictionless lead = wires?

Steve H. =

= When I moved here to Aptos, California I was forced to reduce the length of the = boom to L=3D60cm because of limited space as seen in the photos in the link = below and the resulting natural period is now typically 10-12 seconds. Needless to = say, the performance these Lehmans are marginal and I live near the ocean and = the wave action causes them to osculate during storms. =

=

You should be = able to get 30 seconds out of a 60 cm arm quite OK. Most period limitations are = caused by a poor lower suspension, such as a point in a cup or knife edge. It = improves the period if you put the mass at the end of the arm.
Use 3/4" square or round Al = tube for the arm - definitely not solid. You want to keep the arm light but rigid compared to the mass. I use 15 mm SS water pipe + plumbing fittings
The bottom hinge should be ball on = a plane or crossed cylinder. You put the SS ball on the upright and the SS / WC = plane / SS blade the end of the arm. For WC rod, you can use 1/8" Tungsten = Carbide drill shanks, with the vertical on the upright. See www.smallparts.com. = You can also buy type 416 SS 1/4" shoulder bolts from McMaster Carr. www.mcmaster.com
If you construct a double T frame = similar to http://www.bgs.ac.uk/education/school_seismology/seismometer.html you = can set up the system and then trim the response - all adjustments are = sequential, not inter related like on the psn designs. This makes setup and = adjustment far easier. The red block is a support, with a horizontal damping blade and = the sliding damping magnet is placed on the bottom frame. The coil is fixed = to the outside end and swings between the other magnet block. The diagonal Al = support tube prevents rotation.
I used 3" x 1" Al U = Channel with triangular 6" x 6" x 1/8" Al plates to support the joint = in the prototype. This is easy to make and to set up. I use 1/4" SS = bolts.

My suggestion is to use = the calculation seen on this list to determine the boom length you desire. = Then plan the design based on that calculation. You said you wanted a device = with a period of 20-second and as pointed out below by Chris, L is based on the = length of the boom measured from the pivot point to the center of the mass = weight (Chris, do you have this calculation?). I have found that setting the = device up this way also reduces the impact of ground deformation (boom does not = remains level and centered) over time which improves the overall operation of = the device keeping the boom off the stops.
http://pw2.netcom.c= om/~shammon1/AptosStn.htm

If the distance = between the hinge and the centre of mass is L metres and the suspension angle is = A, the period T =3D 2xPixSqrt(L / (9.81 x sin(A))) I use 0.56 m which would = give a 1.5 sec pendulum if held vertically. A is ~1/3 degree.
Alnico magnets are now quite = expensive. NdFeB magnets are much cheaper and give a much higher output. For damper = and coil designs - click on Lehman at http://jclahr.com/science/psn/chapman/ = Make the damping blade wide so that it covers both magnets at all times as = shown.
There is also an alternative design = under muventures.
The boom does not have to be level, = but it should be adjusted parallel with the lower frame. Then you can simply = slide the damping magnet further over the horizontal damping blade to adjust the = damping.
You adjust the whole rigid frame to = centre the arm and to set the period. I use three SS plates glued to the = concrete floor for the screw adjusters. I glued SS bearings into the end of the = adjust bolts. Then they don't move about / wander when you adjust them. The SS mounting nuts are glued to the underside of the frame.

Regards,

Chris = Chapman =

&= nbsp; Put the coil on the arm and the magnet on the base. If you put a magne= t on the arm, you will pick up a lot of magnetic noise from the house wiring= , passing trains and lorries etc.
Update 2/14/08: Thanks Chris, I=E2=80=99ll try mounting the coil on the boo= m in the next revision. I never wanted to deal with the lead wires off the r= ear of the boom. Do you have any tips for frictionless lead wires?

Hi Steve,

I mount two 2 mm banana sockets on the=20= end of the arm and two nearby on the frame. I use a ~4" loop of 38 AWG polyu= rethane insulated copper wire soldered between two 2 mm banana plugs. You ca= n solder the insulated wire directly with a hot iron - the insulation just m= elts. I coat the plugs with Vaseline after soldering and before insertion. T= he wires are bent to form a vertical 'hairpin' V. This has very little effec= t on the mechanical balance and a low electrical resistance. I use twin core= braid screened microphone cable to connect up. You can use gold plated D tw= in plastic connectors. You can also mount insulated pins on the arm and fram= e and solder wires directly, but dismounting and adjusting the arm is easier= if you can just unplug the connectors.

The biggest improvement that you could=20= make would be to replace the point in a cup lower support with a 1/4" SS bal= l bearing on the end of the mounting bolt and stick a SS blade flat or a WC=20= triangle on the end of the arm. This would enable you to extend the period t= o at least 20 seconds.
An alternative would be to buy a 1/8" t= ungsten carbide drill bit and cut the shank in two. This would give you two=20= cylinders for a crossed cylinder rolling suspension. The vertical goes on th= e frame. Both systems work well.
I don't know where point in a cup or kn= ife edge 'bearings' originated, but they automatically fail in use as you ov= erload the tip / edge and they then limit the performance. The 'knife edge'=20= bearings used in chemical balances don't actually have a knife edge! The 60=20= degree triangle is lapped to a tiny radius cylinder rolling on a flat.

I did a rough comparison with the outpu= t of a coil using a U Alnico magnet and a Quad of NdFeB bar magnets on 1/4"=20= backing plates. The improvement was > x10. My original coil was about 6,0= 00 turns, but I have reduced this to 2,000 to keep the output from overloadi= ng my amplifier on the lowest gain setting. See drawings on http://jclahr.co= m/science/psn/chapman/lehman/index.html

I hope that this helps.

Regards,

Chris Chapman
Subject: Re: new style vertical seismometer From: "meredith lamb" paleoartifact@......... Date: Thu, 14 Feb 2008 22:34:22 -0700 Hi Randall, Any possiblity of a close up of the ball point hinge arrangement? The picture can't define what anchors the pen assembly or in which direction, or what the ball points contacts. Either way it "looks" like it might be a little difficult to initially set up; i.e., the spring would have to be adjusted just right for it to be reasonably consistently stable. I suppose you've also tried having the ball points resting atop the cross rectangular piece at one time or the other....but I'd guess the pressure is too much there. Thanks, Meredith Lamb On Thu, Feb 14, 2008 at 11:56 AM, Randall Peters wrote: > Those of you who like to build things might want to try your hand at a new > design for the old > LaCoste spring vertical seismometer. Internal friction that limits > performance has with > previous designs been mainly concentrated in both (i) spring, and (ii) > axis. My design can > radically reduce the hinge force influence, which should improve > performance. A prototype is > pictured at http://physics.mercer.edu/hpage/new-z.html > The key to the smaller reaction forces at the hinge (pair of > ball-point pens) is to add an angled > boom appendage that allows the zero-length spring itself to be vertical, > as opposced to the usual > orientation (inclined)--and to place the inertial masses such that the > center of mass is close to where the > spring passes through the split region of the horizontal segment of the > boom. > Although the prototype is shown with an SDC array to sense > displacement, the instrument can be > configured to operate with a magnet/coil (Faraday-law) velocity sensor. > > Randall > >
Hi Randall,

Any possiblity of a close up of the ball point hinge arrangement?  The picture can't define
what anchors the pen assembly or in which direction, or what the ball points contacts.

Either way it "looks" like it might be a little difficult to initially set up; i.e., the spring would
have to be adjusted just right for it to be reasonably consistently stable.

I suppose you've also tried having the ball points resting atop the cross rectangular piece
at one time or the other....but I'd guess the pressure is too much there.

Thanks, Meredith Lamb

On Thu, Feb 14, 2008 at 11:56 AM, Randall Peters <PETERS_RD@..........> wrote:
Those of you who like to build things might want to try your hand at a new design for the old
LaCoste spring vertical seismometer.  Internal friction that limits performance has with
previous designs been mainly concentrated in both (i) spring, and (ii) axis.  My design can
radically reduce the hinge force influence, which should improve performance. A prototype is
pictured at  http://physics.mercer.edu/hpage/new-z.html
The key to the smaller reaction forces at the hinge (pair of ball-point pens) is to add an angled
boom appendage that allows the zero-length spring itself to be vertical, as opposced to the usual
orientation (inclined)--and to place the inertial masses such that the center of mass is close to where the
spring passes through the split region of the horizontal segment of the boom.
Although the prototype is shown with an SDC array to sense displacement, the instrument can be
configured to operate with a magnet/coil (Faraday-law) velocity sensor.

Randall

Subject: Explosives vs. calibration From: "Fikke, Audun" Audun.Fikke@......... Date: Fri, 15 Feb 2008 11:09:10 +0100 All, I've just learned that during easter the harbour will be opened up with explsives, 2km from where I live (Stavanger/Norway). They will be using 120metric tonnes of explosives. I belive they will do it in one blast. I don't have confirmation on type of explosives yet (TNT,dynamite,C4,firecrackers....) Does anybody have an idea if this could be used as a benchmark for my seismometer in regards to get a usable calibration? I'm thinking Velocity/Accelleration/Displacement? =20 regards Audun http://vindkast.no =20 =20
All,
I've just = learned=20 that during easter the harbour will be opened up with explsives, = 2km from=20 where I live (Stavanger/Norway).
They will be = using=20 120metric tonnes of explosives. I belive they will do it in one blast. I = don't=20 have confirmation on type of explosives yet=20 (TNT,dynamite,C4,firecrackers....)
Does anybody = have an idea=20 if this could be used as a benchmark for my seismometer in regards = to get a=20 usable calibration? I'm thinking=20 Velocity/Accelleration/Displacement?

regards
Audun
http://vindkast.no

The teacher how is helping me b= uilding the seismometer wants to know
what type of material is best to use in the seismometer. He was
wondering about iron or steel, maybe aluminum. But as I am not sure so I
was unable to give him good answer. He was also wondering about the arm
that holds them mass up, what it should me made out of.

I am going to use the BGS design, as it has the configuration numbers
that the teacher needs to build the seismometer.

Hi Jon,

I suggest that you download and read ft= p://ftp.bgs.ac.uk/pubload/schoolseismology/SEP_CD/SSS_instructions_v1.pdf        The original version used 2.5" or 3" x=20= 1" U Channel Aluminum for the frame and  1/8" Al plate for the corners.= It used 6mm SS bolts.
You can buy 1/8" / 3mm Tungsten Carbide= drills and use the shanks for the bearings

This should give you some ideas anyway!=

Regards,

Chris Chapman
Subject: Re: seismometer performance From: Bobhelenmcclure@....... Date: Fri, 15 Feb 2008 21:13:05 EST Hi all, Brett, you did a beautiful job with your paper on force feedback. I can almost understand it! One issue discussed but unresolved is how to handle drift. Have you ever looked at the efforts of one of our PSN members, Allan Coleman. He has built a number of force feedback sensors of both horizontal and vertical types. His designs feature the use of motors to recenter the pendulum. His website is: http://mysite.verizon.net/ressczez/homebuilt_seismometers/ You can also access it from a link in: http://www.jclahr.com/science/psn Look for "Allan Coleman's seismometer designs". Force rebalance is a necessity for network sensors. All need a flat response that is known and stable. As for me, there is too much involved circuitry to cope with. I choose to use conventional open loop sensors of known period and damping, and then to make their response flat and broadband using my inverse filter program, "WQFilter.exe". This utility is available for download from http://jclahr.com/science/psn/mcclure/sac/index.html Regards, Bob PSN Station REM Locust Valley, NY ************** The year's hottest artists on the red carpet at the Grammy Awards. Go to AOL Music. (http://music.aol.com/grammys?NCID=aolcmp00300000002565) Hi all,

Brett, you did a beautiful job with your paper on force feedback. I c= an almost understand it! One issue discussed but unresolved is how to handle= drift. Have you ever looked at the efforts of one of our PSN members, Allan= Coleman. He has built a number of force feedback sensors of both horizontal= and vertical types. His designs feature the use of motors to recenter the p= endulum.

His website is:

http://mysite.verizon.net/ressczez/homebuilt_seismometers/

You can also access it from a link in:

http://www.jclahr.com/science/psn

Look for "Allan Coleman's seismometer designs".

Force rebalance is a necessity for network sensors. All need a flat r= esponse that is known and stable. As for me, there is too much involved circ= uitry to cope with. I choose to use conventional open loop sensors of known=20= period and damping, and then to make their response flat and broadband using= my inverse filter program, "WQFilter.exe". This utility is available for do= wnload from

http://jclahr.com/science/psn/mcclure/sac/index.html

Regards,

Bob
PSN Station REM
Locust Valley, NY

**************
The year's hottest art= ists on the red carpet at the Grammy Awards. Go to AOL Music.
(http= ://music.aol.com/grammys?NCID=3Daolcmp00300000002565) Subject: Re: nature of the mesoscopic nonlinearity From: ChrisAtUpw@....... Date: Fri, 15 Feb 2008 21:29:34 EST In a message dated 2008/02/15, Brett3mr@............. writes: > >>Numerical integration looks interesting. What I think I need to make it > >>work is a D/A with something like 24-bit resolution and correspondingly > low > >>noise. Haven't looked too hard, and haven't found any. > > > > There are some about. > > Any suggestions as to what manufacturers to check? Texas, Burr-Brown They do 20 bit single channel, DAC1220E. Most of the 24 bit ones seem to be audio codecs. I don't know what their error or stability are like. > > The STS-2 goes to this. Particular versions of the STS-1 would go > > out to 1,000 seconds. It is a very hard way to get this performance! > > Given the fundamental noise issues in any vertical, I think it's the only > way. Only because you are using a particular feedback loop method involving velocity feedback. If you measure the position and relate the movement digitally, you should not have problems over period. > > There is a lot of earth noise down to the Eigenmodes, which are > > interesting in themselves. Transient signals occur which look very like > > quake precursors. > > Those transients worry me just a little. What worries you about them? I find the prospect both interesting and exciting! The crust of the Earth is being continually cyclically flexed by the Sun and the Moon. It would be very surprising if there were NO transients! You also get Earth Hum. > >>Not sure how you are proposing to reduce the restoring force. If you are > >>suggesting feedback, it actually doesn't act in that way. > > > > Positive feedback does and it will increase the period. > > Sounds like an oscillator to me. Then you may be misunderstanding something. There is no reason why you should not provide a weaker spring / seek to reduce the force required to move the mass by feedback. You can certainly get an oscillator this way, but only if you generate a net positive force, not reduce a negative one. > > You are using a position sensor, which will have a measurement > > range and a noise level which limits what you can sense. I am enquiring > > what resolution you can get. The practical limit is likely to be set > > above this by thermal variations. > > Using the same C/D device, a little better than the SDC, maybe 5-10x the > displacement sensitivity depending on the plate size, so 5-10x S/N. I > have been scratching my head as to how to characterize C/D quantization > noise relative to feedback. I'm sure as you apply feedback, reducing the > sensitivity, the displacement corresponding to one C/D step also reduces, > so S/N from that source shouldn't get worse. I need to think about this > more. If you apply strong feedback, the detector will not 'know' anything about it, but the mass movement for a given quake amplitude will be decreased. You will be requiring increased resolution and this conflicts with stability / drift. You can fit fixed capacitors to the system and then measure the actual output noise that you get. This is what we did with Barzilai's circuit and the sine wave circuit. I don't see how you can calculate it. The digital method is inferior due to it's sensitivity to tiny variations in timing. > >> > A capacitative position sensor system can have a very high > >> > linearity. What other system nonlinearities were you considering that > >> > could be relevant? > >> > >>Primarily the position sensor system. That would include, of course, the > >>C/D converter as well as the capacitor. When you say very high linearity > >>are you implying 1%, 0.1%, 0.01%....? Have any measurements been made? > > > > My guesstimate would be in the 0.1% region, but probably better. It > will > > depend mostly on the precision of the physical sensor construction. The > > linearity over a small range will be extreme. > > OK, sometime I'll play around with numbers in that range and see what > happens. Regards, Chris In a me= ssage dated 2008/02/15, Brett3mr@............. writes:

>>Numerical integration l= ooks interesting.  What I think I need to make it
>>work is a D/A with something like 24-bit resolution and correspondin= gly low
>>noise.  Haven't looked too hard, and haven't found any.
>

Any suggestions as to what manufacturers to check?

Texas, Burr-Brown They do 20 bit singl= e channel, DAC1220E. Most of the 24 bit ones seem to be audio codecs. I don'= t know what their error or stability are like.

>    &nb= sp;   The STS-2 goes to this. Particular versions of the STS-1 wou= ld go
> out to 1,000 seconds. It is a very hard way to get this performance!
Given the fundamental noise issues in any vertical, I think it's the only wa= y.

Only because you are using a particula= r feedback loop method involving velocity feedback. If you measure the posit= ion and relate the movement digitally, you should not have problems over per= iod.

>    &nb= sp;   There is a lot of earth noise down to the Eigenmodes, which=20= are
> interesting in themselves. Transient signals occur which look very like=
> quake precursors.

Those transients worry me just a little.

What worries you about them? I find th= e prospect both interesting and exciting! The crust of the Earth is being co= ntinually cyclically flexed by the Sun and the Moon. It would be very surpri= sing if there were NO transients! You also get Earth Hum.

>>Not sure how you are pr= oposing to reduce the restoring force.  If you are
>>suggesting feedback, it actually doesn't act in that way.
>
>    Positive feedback does and it will increase the perio= d.

Sounds like an oscillator to me.

Then you may be misunderstanding somet= hing. There is no reason why you should not provide a weaker spring / seek t= o reduce the force required to move the mass by feedback. You can certainly=20= get an oscillator this way, but only if you generate a net positive force, n= ot reduce a negative one.

>    &nb= sp;   You are using a position sensor, which will have a measureme= nt
> range and a noise level which limits what you can sense. I am enquiring=
> what resolution you can get. The practical limit is likely to be set > above this by thermal variations.

Using the same C/D device, a little better than the SDC, maybe 5-10x the displacement sensitivity depending on the plate size, so 5-10x S/N.  I=20=
have been scratching my head as to how to characterize C/D quantization
noise relative to feedback.  I'm sure as you apply feedback, reducing t= he
sensitivity, the displacement corresponding to one C/D step also reduces, so S/N from that source shouldn't get worse.  I need to think about thi= s more.

If you apply strong feedback, the dete= ctor will not 'know' anything about it, but the mass movement for a given qu= ake amplitude will be decreased. You will be requiring increased resolution=20= and this conflicts with stability / drift.
You can fit fixed capacitors to the sys= tem and then measure the actual output noise that you get. This is what we d= id with Barzilai's circuit and the sine wave circuit. I don't see how you ca= n calculate it. The digital method is inferior due to it's sensitivity to ti= ny variations in timing.

>> >   =    A capacitative position sensor system can have a very high
>> > linearity. What other system nonlinearities were you consideri= ng that
>> > could be relevant?
>>
>>Primarily the position sensor system.  That would include, of c= ourse, the
>>C/D converter as well as the capacitor.  When you say very high= linearity
>>are you implying 1%, 0.1%, 0.01%....?  Have any measurements be= en made?
>
>     My guesstimate would be in the 0.1% region, but= probably better. It will
> depend mostly on the precision of the physical sensor construction. The=
> linearity over a small range will be extreme.

OK, sometime I'll play around with numbers in that range and see what happen= s.

Regards,

Chris
Subject: RE: new style vertical seismometer From: Michael Kimzey mckimzey@........... Date: Fri, 15 Feb 2008 21:57:42 -0500 Great design, Dr. Peters. =20 A question, though. The web page mentions a feedback system to increase th= e period. What would such a system look like? - Mike > Date: Thu, 14 Feb 2008 13:56:00 -0500 > From: PETERS_RD@.......... > Subject: new style vertical seismometer > To: psn-l@.............. >=20 > Those of you who like to build things might want to try your hand at a ne= w design for the old > LaCoste spring vertical seismometer. Internal friction that limits perfo= rmance has with > previous designs been mainly concentrated in both (i) spring, and (ii) ax= is. My design can > radically reduce the hinge force influence, which should improve performa= nce. A prototype is > pictured at http://physics.mercer.edu/hpage/new-z.html > The key to the smaller reaction forces at the hinge (pair of ball-po= int pens) is to add an angled > boom appendage that allows the zero-length spring itself to be vertical, = as opposced to the usual > orientation (inclined)--and to place the inertial masses such that the ce= nter of mass is close to where the > spring passes through the split region of the horizontal segment of the b= oom. > Although the prototype is shown with an SDC array to sense displaceme= nt, the instrument can be > configured to operate with a magnet/coil (Faraday-law) velocity sensor. >=20 > Randall >=20
Great design, Dr= .. Peters.

A question, though.  The web page mentions a f= eedback system to increase the period.  What would such a system look = like?

- Mike

> Date:= Thu, 14 Feb 2008 13:56:00 -0500
> From: PETERS_RD@..........
>= Subject: new style vertical seismometer
> To: psn-l@..............>
> Those of you who like to build things might want to try you= r hand at a new design for the old
> LaCoste spring vertical seismome= ter. Internal friction that limits performance has with
> previous d= esigns been mainly concentrated in both (i) spring, and (ii) axis. My desi= gn can
> radically reduce the hinge force influence, which should imp= rove performance. A prototype is
> pictured at http://physics.mercer= ..edu/hpage/new-z.html
> The key to the smaller reaction forces a= t the hinge (pair of ball-point pens) is to add an angled
> boom appe= ndage that allows the zero-length spring itself to be vertical, as opposced= to the usual
> orientation (inclined)--and to place the inertial mas= ses such that the center of mass is close to where the
> spring passe= s through the split region of the horizontal segment of the boom.
> = Although the prototype is shown with an SDC array to sense displacement,= the instrument can be
> configured to operate with a magnet/coil (Fa= raday-law) velocity sensor.
>
> Randall
>

Those of you who like to build=20= things might want to try your hand at a new design for the old LaCoste sprin= g vertical seismometer.

Hi Randall,

I note that you mention using a zero le= ngth spring. The extension springs that you can buy do not have such a high=20= preload - usually about 1/3 of that required. Are you winding your own?

What hard counterface are you using for= the WC 1 mm bearings? They have quite a restricted load carrying capacity (= 100 gm?), but, unlike the Volksmeter, the seismic mass is quite heavy.

How does the seismometer cope with vert= ical inertial loads of up to 0.1 g and horizontal loads of an appreciable fr= action of this? How do you avoid overloading these very small bearings? What= is supposed to maintain the horizontal positional stability? While a vertic= al seismometer is only sensitive to vertical loads, it experiences both vert= ical and horizontal displacements while in operation.

Regards,

Chris Chapman
Subject: FW: Explosives vs. calibration From: "Fikke, Audun" Audun.Fikke@......... Date: Sat, 16 Feb 2008 18:11:02 +0100 =20 All, I've just learned that during easter our harbour will be opened up with explsives, 2km from where I live (Stavanger/Norway). They will be using 120metric tonnes of explosives.=20 Does anybody have an idea if this could be used as a benchmark for my seismometer in regards to get a usable calibration? I'm thinking down the road of Velocity/Accelleration/Displacement? =20 The guys involved in the blast must have some calculations ready as part of the pre job planning/safety. And I can contact them if you guys think It's worth pursuing. regards Audun =20 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: seismometer performance From: ChrisAtUpw@....... Date: Sat, 16 Feb 2008 12:28:23 EST In a message dated 2008/02/16, Brett3mr@............. writes: > If carried down to low enough frequency, integral feedback can go a long > way toward resisting instrument drift. This is 'just' a matter of making > the instrument force / acceleration response approach zero at very low > frequencies. > > Unfortunately, there is dirty little secret about using R-C integral > feedback to resist drift error forces, and that is evident when the > integrator is 'straining' to cancel a fairly strong unbalance force, in > which event there will be a substantial voltage across the integrating > capacitor. The cap. has a temperature coefficient of C which is of the > same order of magnitude as the Temp. Coeff. of a steel spring i.e. pretty > large. Since in a feedback integrator the charge, Q in the cap. changes > relatively slowly and can be considered to be constant as a first > approximation, if its capacitance goes up with temperature, its voltage > goes down in proportion because of Q=CV thus introducing its own rather > large drift effect. It will only work as expected if the system is already > reasonably well balanced mechanically making the voltage across the cap. > not too large. Hi Brett, You have four drifts here. The change in the magnet strength with temperature, the changes in the coil with temperature and the change in the capacitor with temperature. The magnet strength is decreasing, the coil area and resistance are increasing and the capacitance is decreasing with increasing T. I don't know to what extent these can be chosen to cancel? However, you only have to put the low pass frequency below the minimum response frequency, but this could give problems with 1000 second instruments. Regards, Chris Chapman In a me= ssage dated 2008/02/16, Brett3mr@............. writes:

If carried down to low enough f= requency, integral feedback can go a long
way toward resisting instrument drift.  This is 'just' a matter of maki= ng
the instrument force / acceleration response approach zero at very low
frequencies.

Unfortunately, there is dirty little secret about using R-C integral
feedback to resist drift error forces, and that is evident when the
integrator is 'straining' to cancel a fairly strong unbalance force, in
which event there will be a substantial voltage across the integrating
capacitor.  The cap. has a temperature coefficient of C which is of the=
same order of magnitude as the Temp. Coeff. of a steel spring i.e. pretty large.  Since in a feedback integrator the charge, Q in the cap. change= s
relatively slowly and can be considered to be constant as a first
approximation, if its capacitance goes up with temperature, its voltage
goes down in proportion because of Q=3DCV thus introducing its own rather large drift effect.  It will only work as expected if the system is alr= eady
reasonably well balanced mechanically making the voltage across the cap. not too large.

Hi Brett,

You have four drifts here. The change i= n the magnet strength with temperature, the changes in the coil with tempera= ture and the change in the capacitor with temperature. The magnet strength i= s decreasing, the coil area and resistance are increasing and the capacitanc= e is decreasing with increasing T. I don't know to what extent these can be=20= chosen to cancel? However, you only have to put the low pass frequency below= the minimum response frequency, but this could give problems with 1000 seco= nd instruments.

Regards,

Chris Chapman
Subject: Re: FW: Explosives vs. calibration From: ChrisAtUpw@....... Date: Sat, 16 Feb 2008 12:38:33 EST In a message dated 2008/02/16, Audun.Fikke@......... writes: > I've just learned that during easter our harbour will be opened up with > explsives, 2km from where I live (Stavanger/Norway). They will be using > 120metric tonnes of explosives. > Does anybody have an idea if this could be used as a benchmark for my > seismometer in regards to get a usable calibration? I'm thinking down > the road of Velocity/Accelleration/Displacement? Hi Audun, You don't say what seismometer you are using? I would be inclined to pack up and take my seismometer on holiday at that time. I regard 120 tons of HE at 2 km as far too close for comfort for either of us. Regards, Chris Chapman In a me= ssage dated 2008/02/16, Audun.Fikke@......... writes:

I've just learned that during e= aster our harbour will be opened up with explsives, 2km from where I live (S= tavanger/Norway). They will be using 120metric tonnes of explosives.
Does anybody have an idea if this could be used as a benchmark for my
seismometer in regards to get a usable calibration? I'm thinking down

Hi Audun,

You don't say what seismometer you are=20= using? I would be inclined to pack up and take my seismometer on holiday at=20= that time. I regard 120 tons of HE at 2 km as far too close for comfort for=20= either of us.

Regards,

Chris Chapman
Subject: Re: seismometer performance From: Brett Nordgren Brett3mr@............. Date: Sat, 16 Feb 2008 13:50:42 -0500 Hi Chris, At 12:28 PM 2/16/2008 -0500, you wrote: >In a message dated 2008/02/16, Brett3mr@............. writes: > >>If carried down to low enough frequency, integral feedback can go a long >>way toward resisting instrument drift. This is 'just' a matter of making >>the instrument force / acceleration response approach zero at very low >>frequencies. >> >>Unfortunately, there is dirty little secret about using R-C integral >>feedback to resist drift error forces, and that is evident when the >>integrator is 'straining' to cancel a fairly strong unbalance force, in >>which event there will be a substantial voltage across the integrating >>capacitor. The cap. has a temperature coefficient of C which is of the >>same order of magnitude as the Temp. Coeff. of a steel spring i.e. pretty >>large. Since in a feedback integrator the charge, Q in the cap. changes >>relatively slowly and can be considered to be constant as a first >>approximation, if its capacitance goes up with temperature, its voltage >>goes down in proportion because of Q=CV thus introducing its own rather >>large drift effect. It will only work as expected if the system is already >>reasonably well balanced mechanically making the voltage across the cap. >>not too large. > > >Hi Brett, > > You have four drifts here. The change in the magnet strength with > temperature, the changes in the coil with temperature and the change in > the capacitor with temperature. The magnet strength is decreasing, the > coil area and resistance are increasing and the capacitance is decreasing > with increasing T. I don't know to what extent these can be chosen to > cancel? However, you only have to put the low pass frequency below the > minimum response frequency, but this could give problems with 1000 second > instruments. Yes, I agree the forcing coil/magnet also introduce effects similar to what I was describing for the integrator capacitor; except that you can avoid the coil resistance issues by using a current driver. It's obvious that you can't depend on electronic feedback to do all your centering, forever, but must occasionally turn a screw to unload the feedback loop. Thanks for your thoughts, Brett __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: seismometer performance From: ChrisAtUpw@....... Date: Sat, 16 Feb 2008 17:28:45 EST In a message dated 2008/02/16, Brett3mr@............. writes: > Yes, I agree the forcing coil/magnet also introduce effects similar to what > > I was describing for the integrator capacitor; except that you can avoid > the coil resistance issues by using a current driver. It's obvious that > you can't depend on electronic feedback to do all your centering, forever, > but must occasionally turn a screw to unload the feedback loop. Hi Brett, My train of thought was to either compensate or to drastically reduce the main error drifts. I use a small thermostat circuit to keep crystal temperatures constant to better than 0.1 C Deg. I could wrap one nicely around a capacitor. If you used an electromagnet, you could keep the field constant to a few ppm. An alternative would be to control the temperature of the magnets. The biggest drift is likely that of a steel spring. Can you get Ni-SpanC wire? sheet? I can get Invar wire, but not Elinvar at the moment. Regards, Chris Chapman In a me= ssage dated 2008/02/16, Brett3mr@............. writes:

Yes, I agree the forcing coil/m= agnet also introduce effects similar to what
I was describing for the integrator capacitor; except that you can avoid the coil resistance issues by using a current driver.  It's obvious tha= t
you can't depend on electronic feedback to do all your centering, forever, <= BR> but must occasionally turn a screw to unload the feedback loop.
=

Hi Brett,

My train of thought was to either compe= nsate or to drastically reduce the main error drifts. I use a small thermost= at circuit to keep crystal temperatures constant to better than 0.1 C Deg. I= could wrap one nicely around a capacitor. If you used an electromagnet, you= could keep the field constant to a few ppm. An alternative would be to cont= rol the temperature of the magnets.
The biggest drift is likely that of a s= teel spring. Can you get Ni-SpanC wire? sheet? I can get Invar wire, but not= Elinvar at the moment.

Regards,

Chris Chapman
Subject: Re: FW: Explosives vs. calibration<<< Hmmmm........ From: "Jim ODonnell" geophysics@.......... Date: Sun, 17 Feb 2008 00:44:49 GMT Audun- You may be looking at ~M3.5+ at 2km which is rather Awesome.... See Prof John Louie's chart at UNR relating EQ Mag to seismic energy Yie= ld: = = http://www.seismo.unr.edu/ftp/pub/louie/class/100/magnitude.html It depends on the coupling and if it is a ripple shot rather than 1 big = bang. <<<<<<<<<< Jim Jim O'Donnell = Geological/Geophysical Consultant GEOTECHNICAL APPLICATIONS 702.293.5664 geophysics@.......... 702.281.9081 cell jimo17@........ -- "Fikke, Audun" wrote: All, I've just learned that during easter our harbour will be opened up with explsives, 2km from where I live (Stavanger/Norway). They will be using 120metric tonnes of explosives. = Does anybody have an idea if this could be used as a benchmark for my seismometer in regards to get a usable calibration? I'm thinking down the road of Velocity/Accelleration/Displacement? The guys involved in the blast must have some calculations ready as part= of the pre job planning/safety. And I can contact them if you guys think= It's worth pursuing. regards Audun __________________________________________________________ Public Seismic Network Mailing List (PSN-L) See http://www.seismicnet.com/maillist.html for more information.

Audun- You may be looking at ~M3.5+ at 2km which is rather = ;Awesome....
See Prof John Louie's chart at UNR relating EQ Mag to se= ismic energy Yield:

http://www.seismo.unr.edu/ftp/pub= /louie/class/100/magnitude.html

It depends on the coupling and if it is a ripple shot rather than 1 b= ig bang.
<<<<<<<<<<   Jim
=

&nbs= p;       Jim O'Donnell   &n= bsp;
Geological= /Geophysical Consultant
&nb= sp;   GEOTECHNICAL APPLICATIONS
702.293.5664  &nb= sp; geophysics@..........
702.281.9081 cell   jimo17@j= uno.com

-- "Fikke, Audun" <Audun.Fikke@.........> wrote:

All,
I've just learned that during easter our harbour will b= e opened up with
explsives, 2km from where I live (Stavanger/Norway).=
They will be using 120metric tonnes of explosives.
Does anybody = have an idea if this could be used as a benchmark for my
seismometer = in regards to get a usable calibration? I'm thinking down

The guys involved in the bl= ast must have some calculations ready as part
of the pre job planning= /safety. And I can contact them if you guys think
It's worth pursuing= ..

regards
Audun

_______________________________________= ___________________

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

Subject: Re: when feedback is not needed From: Barry Lotz barry_lotz@............. Date: Sat, 16 Feb 2008 16:49:01 -0800 (PST) Randall Something has confused me about the volksmeter or the SG sensor. For a passive sensor I always thought the response of the sensor dropped by (I forget the db slope) for frequencies below the natural frequency of the sensor. Therefore I would think the output would have to amplified accordingly for low frequencies. Is the noise amplified also? Is the drop-off mathematically known so the amplification can be correctly compensated? I didn't think a simple intergator in the output of the SG provided a simple flat response of output vs frequency. Regards Barry Randall Peters wrote: Recent discussions of force feedback have mentioned pendulums. I hope that these were thoughts directed only toward horizontal instruments of the 'garden gate' variety (not what I call a pendulum); since I can't imagine a reason for ever wanting to go to that degree of difficulty with a 'simple' pendulum such as in the VolksMeter. The direction of a simple static pendulum does not migrate to any great extent. Its very low frequency response is determined by shape changes of the earth that do not exceed tens of microradians. The exception to this claim applies only to the case of a detector with a very limited mechanical dynamic range, such as a gap varying capacitive sensor. With the area-varying array used by the VoksMeter it is unlikely that force balance or any other type of feedback should ever be needed. Randall begin:vcard n:Peters;Randall tel;work:(478)301-2747 x-mozilla-html:FALSE url:http://physics.mercer.edu/hpage/peters.html org:Mercer University;Physics Department adr:;;1400 Coleman Ave.;Macon;Georgia;31207;USA version:2.1 email;internet:peters_rd@.......... title:Professor and Chairman fn:Randall Peters PhD end:vcard
Randall
Something has confused me about the volksmeter or the SG sensor. For a passive sensor I always thought the response of the sensor dropped by (I forget the db slope) for frequencies below the natural frequency of the sensor. Therefore I would think the output would have to amplified accordingly for low frequencies. Is the noise amplified also? Is the drop-off mathematically known so the amplification can be correctly compensated? I didn't think a simple intergator in the output of the SG provided a simple flat response of output vs frequency.
Regards
Barry

Randall Peters <PETERS_RD@..........> wrote:
Recent discussions of force feedback have mentioned pendulums. I hope that these were thoughts directed only toward horizontal
instruments of the 'garden gate' variety (not what I call a pendulum); since I can't imagine a reason for ever wanting to go to
that degree of difficulty with a 'simple' pendulum such as in the VolksMeter. The direction of a simple static pendulum does
not migrate to any great extent. Its very low frequency response is determined by shape changes of the earth that do not exceed
tens of microradians. The exception to this claim applies only to the case of a detector with a very limited mechanical dynamic
range, such as a gap varying capacitive sensor. With the area-varying array used by the VoksMeter it is unlikely that force
balance or any other type of feedback should ever be needed.
Randall

begin:vcard
n:Peters;Randall
tel;work:(478)301-2747
x-mozilla-html:FALSE
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org:Mercer University;Physics Department
version:2.1
email;internet:peters_rd@..........
title:Professor and Chairman
fn:Randall Peters PhD
end:vcard

Something has confused me about= the volksmeter or the SG sensor. For a passive sensor I always thought the=20= response of the sensor dropped by (I forget the db slope) for frequencies be= low the natural frequency of the sensor. Therefore I would think the output=20= would have to amplified accordingly for low frequencies. Is the noise amplif= ied also? Is the drop-off mathematically known so the amplification can be c= orrectly compensated? I didn't think a simple intergator in the output of th= e SG provided a simple flat response of output vs frequency.

Hi Barry,

If you use a velocity sensor, the outpu= t falls off below resonance at x100 per decade and stays level above resonan= ce. However, both the SG and the Volksmeter use position sensors which fall=20= off at x10 per decade below resonance. Hence you can extend the period by ab= out 1000 and still get an OK noise level, using a really low noise system. Y= our 0.9 Hz Volksmeter really will work out to 1000 second periods. They also= fall off x10 per decade above resonance..... but you can also compensate OK= for that.
See Brett's recent posting on feedback=20= systems?
http://bnordgren.org/seismo/feedback_in= _seismic_sensors3.pdf

Regards,

Chris Chapman
Randall
It seems that there are two measurements being discussed (horizontal accelerations due to teleseismic events and tilting of the sensor). Accelerometers are designed with a high natural frequency since they are suited to measure displacements below this frequency. Tilting a accelerometer will measure that portion of gravity induced. I think accelerations from a teleseismic events are very very small. I can see how a simple pendulum will act as a tilt meter  if one can remove the possibly changes from temperature, soil moisture gradients ( when sensor is not on bedrock) etc
If a pendulum were very long (as you mentioned) I also believe the measurement of displacement relative to the support would measure the earth displacement from a teleseismic event .It seems to me that bodies at rest tend to stay at rest unless an external force is applied to them (like the restoring force of a short period pendulum which is not allowed to tilt). One would have to correct for the drop off in sensitivity by post processing or with real time electronics or math.
Regards
Barry

Randall Peters <PETERS_RD@..........> wrote:
<clip>
moreover, when monitored with a position rather than velocity sensor, there is no falloff in sensitivity whatsoever when the
frequency is below its natural frequency (unless one stupidly insists on the use of a velocity sensor, which for periods
greater than a few thousand seconds WILL NEVER WORK!).

<clip>

The simple
pendulum would be a GREAT candidate for so doing if I had a facility to hold one whose length were 10 m (or even longer). As
compared to the VolksMeter, it would be 100 times more sensitive in every frequency range. (For tide studies it doesn't need
that sensitivity; but for 20 s period teleseisms, it does.)
Randall

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Subject: Re: Seismograph Noise Probelm From: ChrisAtUpw@....... Date: Sun, 17 Feb 2008 13:11:03 EST In a message dated 2008/02/17, lconklin@............ writes: > I am definitely going to make a new cover, probably out of styrafoam > insulation board. It's light, a good insulator and easy to work with. Hi there, Can I recommend Celotex? It has a styrofoam core covered by two very thin sheets of glass scrim and an Al foil topcoat is then added. This makes it impervious to water, resistant to handling damage and easy to clean. You can stick it together using foam grouting. You can get it in a wide range of thicknesses. Regards, Chris Chapman In a me= ssage dated 2008/02/17, lconklin@............ writes:

I am definitely going to make a= new cover, probably out of styrafoam
insulation board.  It's light, a good insulator and easy to work with.<= /BLOCKQUOTE>

Hi there,

Can I recommend Celotex? It has a styro= foam core covered by two very thin sheets of glass scrim and an Al foil topc= oat is then added. This makes it impervious to water, resistant to handling=20= damage and easy to clean. You can stick it together using foam grouting. You= can get it in a wide range of thicknesses.

Regards,

Chris Chapman

Hi Randall,

I hear what you say about pendulums and= agree with it. However, I am having a little bit of a problem in relating t= his to seismometers, in which the principle is that the mass stays still - i= t is the Earth which moves / accelerates!

Before we try to reinvent the wheel, pe= rhaps we should consider the history of  past seismometer and linkage t= ypes?

A simple vertical pendulum depends for=20= the resonant period on the length of it's suspension. It is desirable to kee= p this ~1 second , ~25 cm, on grounds of physical size, ease of construction= and freedom from environmental effects.

We can keep about this size, but get mu= ch longer periods if we use either a garden gate suspension, a Romberg linka= ge or a Folded pendulum construction. However, the gg uses two flexures and=20= the other designs use at least 4 sets of flexures, which can, but not necess= arily do, limit their performance. Won't this seriously muck up your suspens= ion flex loss problems, Randall? The reason why you are using ball on a plan= e bearings for the Volksmeter?

The Australians claim to have got about= 90 seconds from a folded pendulum. However, in practical experiments making= up simple FP constructions, it seemed to be difficult to get beyond about 1= 0 seconds. Both the Teds found similar problems. And there is still the huge= tilt sensitivity. I do wonder if the Aussies left something a bit critical=20= out of their write up?

Historically, the period of simple pend= ulums has been varied by reducing the vertical force on the mass. This has b= een done with a vertically mounted spring under the mass, by fitting repelli= ng magnets on the mass and on the ground and by providing a solenoid field t= o attract some iron attached to the mass.

2 second Willmore vertical seismometers= were extended to about 20 seconds with a spring and there are several other= examples applied to inverted pendulums.

There is no reason in principle why you= could not feed a fraction of a position signal back to a vertical coil moun= ted on the mass, to directly reduce the horizontal centring force. I would e= xpect to be able to get x3, maybe x10 increase in the period this way. This=20= is an example of positive feedback less than that required to make the pendu= lum oscillate. An analogy would be to reduce the strength of the spring in a= vertical seismometer.

Note that some quite complicated and cr= itical spring designs have used for LaCoste and Streckeisen vertical seismom= eters. The 'trick' here is to offset the gravitational load in such a way th= at the force change for a small vertical movement is also very small.

Regarding loss in suspension systems, t= he sequence for reducing the loss appears to be Cardan single wires/foils, c= rossed wires/foils, ball on a plane, crossed cylinders and best of all, roll= ing wires/foils. Note that I have deliberately missed out point in a cup and= knife edge suspensions, which are both profoundly unsatisfactory.

In a message dated 2008/02/17, charles.r.patton@........ writes:

There is another possibility ra= ther than the moving pivot as you describe.  Keeping in mind that the b= asic pendulum period is due to the change in height of the bob during the sw= ing that sets the period, then if we flatten the swing, the period will incr= ease.  Therefore starting with the concept that the upper pivot, rather= than the customary shape, a point on a flat supporting surface, is a flat r= olling on a curved
surface.  If this curved surface is such that the height of pendulum is= constant over the swing, then the period is infinite.  Obviously a bit= much.  It also has the problem that the surface is not round, but incr= easingly steep off the center, a recipe for slipping.

I am having great difficulty in visualising this. It seem= s that the bearing plate would have to rotate in the opposite sense to the p= endulum? It is not just the height change that matters; the angle is also im= portant.

So we marry
that with the old=20= Rollamite bearings, to prevent side slip, and put on
(immerse in?) lots of lubricant to prevent stiction
.

Uh Uh! Any liquid lubricant will reall= y foul up such a suspension! Liquid flow and surface tension spring to mind= .. The contact friction is highly variable between lubricated rolling surface= s. You might try fluon spray or dry moly, or rely in the oxide coating.

Regards,

Chris Chapman

Hi Chris,
I agree with the liquid flow question, but I'm not certain I understand
the "...The contact friction is highly variable between lubricated
rolling surfaces."  Are you thinking about surface tension of variable=20=
areas of contact on a non-immersed contact pair?  Wouldn't that
basically disappear if there was total immersion of wetted surfaces and
the oil doesn't use fiberous fillers (such as greases) to thicken it?
=

Surface tension is likely to be the le= ast of your worries.

Grease is a mixture of varios types of=20= soap and oil. A few specialist greases have powder fillers. Moly grease for=20= instance and chassis grease. They prevent metal to metal contact for various= reasons.

If you roll a bearing very slowly, you=20= get full metal to metal contact with very high friction. Increase the speed=20= and the surfaces start to separate on a thin film of oil and the friction dr= ops dramatically. The viscosity of oil is pressure dependant and varies from= a thin fluid to the consistency of solid pitch. It is also time dependant.=20= The rolling surfaces also deform elastically with increasing load and the co= ntact area increases.

P.S. I agree with you that I do= n't know how to fashion the bearing I was
proposing -- a half baked idea in formation, I guess.  But in a separat= e
post I do visit a variation that I think is possible using as a starting point the idea of controlling the height change of a mass to control the   period. I would definitely build it without oil first, then dunk it t= o
see what happens!

I doubt that you will be too happy with= the result. There will be quite large viscous losses as fluid flows from an= d into the rolling contact area. This will be highly rate and temperature de= pendant and non linear.

Regards,

Chris Chapman

See: www.myeclectic.info/Rollin= gPendulum.jpg

Hi Charles,

Cast iron surface plates do corrode, bu= t you could maybe treat it with an organic inhibitor?

The thermal expansion properties will n= eed to be very similar, or changes in the wire may try to rotate the cylinde= r. The wire / cylinder circle will have a high friction tending to prevent a= ny slippage, which is a +.
Maybe use an all SS construction with S= S foil instead of wire? You can buy 30" rolls of 2 thou SS foil from www.ksm= etals.com You could use two end foils and one double width central foil wrap= ped half way around the cylinder just and stuck on at the top?

Have you given any thought as to what s= ensor and / or feedback transducer could be used, please?

Regards,

Chris Chapman
Charles,

You could create the same "rolling" = effect by=20 having 2 narrow plates a short distance apart on the upper edge of = each a=20 shallow curve of about 1000' radius. On these you sit a ground and = polished rod=20 of, say, 2" (~50mm). I'm sure this would give the same effect as your = cylinder,=20 the only problem being of course - the creation of the curves.=20 The measurement of any movement of the rod could be done by some = sort of=20 optical sensor looking either up or down passed a narrower extension of = the rod,=20 or even a flat reflective surface attached to one end of the=20 rod...

Regards

Ted

<tedr@...........>
Subject: Re: From: ChrisAtUpw@....... Date: Tue, 19 Feb 2008 01:34:41 EST In a message dated 2008/02/19, tedr@........... writes: > You could create the same "rolling" effect by having 2 narrow plates a > short distance apart on the upper edge of each a shallow curve of about 1000' > radius. On these you sit a ground and polished rod of, say, 2" (~50mm). I'm sure > this would give the same effect as your cylinder, the only problem being of > course - the creation of the curves. Hi Ted, You could probably get this sort of curvature most easily by flexing a flat plate? It is approximately 0.75 thou for a 6" long plate! Part of the problem is having large area contacts. This is most easily corrected with either strips of foil or wires. Regards, Chris Chapman In a me= ssage dated 2008/02/19, tedr@........... writes:

You could create the same "roll= ing" effect by having 2 narrow plates a short distance apart on the upper ed= ge of each a shallow curve of about 1000' radius. On these you sit a ground=20= and polished rod of, say, 2" (~50mm). I'm sure this would give the same effe= ct as your cylinder, the only problem being of course - the creation of the=20= curves.

Hi Ted,

You could probably get this sort of cur= vature most easily by flexing a flat plate? It is approximately 0.75 thou fo= r a 6" long plate!

Part of the problem is having large are= a contacts. This is most easily corrected with either strips of foil or wire= s.

Regards,

Chris Chapman
Subject: Re: pivots vs bearing structures From: ChrisAtUpw@....... Date: Tue, 19 Feb 2008 02:05:01 EST In a message dated 2008/02/19, Brett3mr@............. writes: > Both those issues were of great interest to pendulum clock makers. The=20 > latter was studed by no less of an authority than Pierre-Simon LaPlace who= =20 > came to two conclusions. First, a (very) small radius would be better tha= n=20 > a knife-edge. Second, it might even be possible to consider a roller. He= =20 > studied the geometry and concluded that the deviation from pendulum arc=20 > circularity was a small fraction of the edge radius. That and very=20 > thorough analyses of flexure suspensions, including effective pivot point=20 > and nonlinear losses are covered in detail in the most excellent book by=20 > A. L. Rawlings "The Science of Clocks & Watches 3rd edition, 1993"=20 Hi Brett, I dug out my copy, but it is unfortunately silent on many of the=20 suspensions that we might want to use. In particular, the rolling wire/foil=20= types=20 have an accurate centre of rotation, extremely low hysteretic loss and ALSO=20 have ZERO TORQUE. The variation of stiffness and torque are two of the probl= ems=20 of Cardan single foil suspensions, but crossed wires/foils are a bit better.= =20 =20 > >So the way I perceive it, a big problem is having a system where the axis= =20 > >of rotation remains constant, quite accurately. Unfortunately the only=20 > >solutions I keep coming back to are bearing style things. So then the=20 > >question becomes, =E2=80=9CCan a bearing be made that has low loss?=E2= =80=9D =20 Categorically yes. But a > concurrent question is do I really need a very low amount of=20 > loss? I know recent discussions have experimented with crossed pivots of=20 > extremely low=20 > >loss. Why? The immediate next step will be to add a damper to get to=20 > >something close to critical damping. My understanding is that the only=20 > >reason to have low loss is to be able to use lots of feedback to lengthen= =20 > >the period. But if the period can be achieved directly, and it includes=20 > >some damping, so what? In my mind, the important item is=20 > >hysteresis/stiction. As bearings and bearing surfaces can easily be=20 > >ground to a ten-thousandth or even better, 10 or 20 second period=20 > >structures should be in reach. Again yes. You need to measure movements down to nano metres, so you=20 need extremely low hysteresis / stiction -.whatever system you use. Feedback= =20 will not compensate for this. > For displacement-to-force feedback and possibly for other configurations,=20= I=20 >=20 > believe you are exactly right. The main reason for having low pivot loss=20 > is to make it 'easy' for the feedback to do its job, resulting in higher=20 > loop gain. In general the pivot losses in such an instrument should have=20 > very little effect on the instrument performance. Consider that the STS-1= =20 > used bearings which I believe had a relatively poor hysteresis spec., yet=20 > its performance was considered to be pretty good. Don't know where you get this from. The STS-1 used crossed foils. The= =20 problems of making the STS-1 eventually lead to it's replacement!=20 > >Back to possible structures. The structure I originally presented is=20 > >probably not possible geometrically. But one that is obviously possible=20 > >is as follows. Imagine a hollow cylinder (like a pipe) that has been=20 > >centerless ground to be round. Now take a high density rod like lead or=20 > >tungsten and center it down the axis of the cylinder with fine adjustment= =20 > >screws so you can offset the center of gravity by a fraction of a=20 > >thousandth.=20 Let's define out objectives. We don't want extreme periods, just mayb= e=20 10 seconds instead of 1 second. Trying to get very long periods makes the=20 task increasingly difficult and the small anelastic effects become major=20 problems, as do thermal variations / expansions. I am fairly confident that you could extend the period by using=20 feedback to SOFTEN the suspension forces of a standard vertical pendulum. Ra= ndall=20 can then keep his 1 mm WC low loss bearings - no problem. Regards, Chris Chapman =20 In a me= ssage dated 2008/02/19, Brett3mr@............. writes:

Both those issues were of great= interest to pendulum clock makers.  The
latter was studed by no less of an authority than Pierre-Simon LaPlace who <= BR> came to two conclusions.  First, a (very) small radius would be better=20= than
a knife-edge.  Second, it might even be possible to consider a roller.&= nbsp; He
studied the geometry and concluded that the deviation from pendulum arc
circularity was a small fraction of the edge radius.  That and very thorough analyses of flexure suspensions, including effective pivot point and nonlinear losses are covered in detail in the most excellent book =20= by
A. L. Rawlings "The Science of Clocks & Watches  3rd edition, 1993"=

Hi Brett,

I dug out my copy, but it is unfortunat= ely silent on many of the suspensions that we might want to use. In particul= ar, the rolling wire/foil types have an accurate centre of rotation, extreme= ly low hysteretic loss and ALSO have ZERO TORQUE. The variation of stiffness= and torque are two of the problems of Cardan single foil suspensions, but c= rossed wires/foils are a bit better.

>So the way I perceive it,=20= a big problem is having a system where the axis
>of rotation remains constant, quite accurately.  Unfortunately the=20= only
>solutions I keep coming back to are bearing style things.  So then=20= the
>question becomes, =E2=80=9CCan a bearing be made that has low loss?=E2= =80=9D

Categorically yes.

But a
concurrent question is do I really need a very low amount of= loss?  I know recent discussions have experimented with crossed pivots= of extremely low
>loss.  Why?  The immediate next step will be to add a damper t= o get to
>something close to critical damping.   My understanding is tha= t the only
>reason to have low loss is to be able to use lots of feedback to lengthe= n
>the period.  But if the period can be achieved directly, and it inc= ludes
>some damping, so what?  In my mind, the important item is
>hysteresis/stiction.   As bearings and bearing surfaces can ea= sily be
>ground to a ten-thousandth or even better, 10 or 20 second period
>structures should be in reach.

Again yes. You need to measure movemen= ts down to nano metres, so you need extremely low hysteresis / stiction -.wh= atever system you use. Feedback will not compensate for this.

For displacement-to-force feedb= ack and possibly for other configurations, I
believe you are exactly right.  The main reason for having low pivot lo= ss
is to make it 'easy' for the feedback to do its job, resulting in higher loop gain.  In general the pivot losses in such an instrument should ha= ve
very little effect on the instrument performance.  Consider that the ST= S-1
used bearings which I believe had a relatively poor hysteresis spec., yet its performance was considered to be pretty good.

Don't know where you get this from. Th= e STS-1 used crossed foils. The problems of making the STS-1 eventually lead= to it's replacement!

>Back to possible structures= ..  The structure I originally presented is
>probably not possible geometrically.  But one that is obviously pos= sible
>is as follows.  Imagine a hollow cylinder (like a pipe) that has be= en
>centerless ground to be round.  Now take a high density rod like le= ad or
>tungsten and center it down the axis of the cylinder with fine adjustmen= t
>screws so you can offset the center of gravity by a fraction of a
>thousandth.

Let's define out objectives. We don't=20= want extreme periods, just maybe 10 seconds instead of 1 second. Trying to g= et very long periods makes the task increasingly difficult and the small ane= lastic effects become major problems, as do thermal variations / expansions.=

I am fairly confident that you could ex= tend the period by using feedback to SOFTEN the suspension forces of a stand= ard vertical pendulum. Randall can then keep his 1 mm WC low loss bearings -= no problem.

Regards,

Chris Chapman

What I'm envisioning is not sig= nificantly different from the folded pendulum in terms of the physics involv= ed.
Before describing it in more detail, let me respond to your comments, Chris.=
Yes, one approach that has been used is to place a spring at the bott= om to 'soften' the restoring force of gravity acting on the pendulum. =20= Although in principle o.k., in fact it has been shown to be unacceptable, du= e to the dastardly properties of springs.  There is no need for such a=20= spring to accomplish the same result.

I note that you have not commented usi= ng magnetic repulsion which has been shown to work!

=20= In the case of the so-called folded pendulum, there are really two pendulums= --one that is 'usual', the other that is inverted. The usual one of the pair= behaves in normal manner; i.e., if disturbed, gravity restores it to equili= brium. The inverted one behaves in just the opposite manner, and provides fo= r a much greater linear response than is possible by using positive feedback= by means of a spring at the bottom of a single pendulum.
Because one pendulum is trying to 'restore' to equilibrium wher= eas the other one ('destoring') is trying to take the system away from equil= ibrium--the net effect of these competing forces is a system with a longer p= eriod. It can be taken all the way to infinite period and beyond (critical p= oint in which conversion from stable equilibrium to unstable equilibrium occ= urs).  Just like any long period seismometer, the material properties l= imit how far one can go in the direction of long-period until it becomes ope= rationally unacceptable (enough to make a preacher cuss).

Several non-preachers have been cussin= g over the practicalities of trying to get a folded pendulum to work OK beyo= nd 10 seconds. With four hinges, you seem to run into suspension stability /= hysteresis problems.

The differen= ce between what I've been discussing and the usual folded pendulum without f= eedback is the following. Instead of two obvious pendulums as with the folde= d, there is a single (usual) pendulum hanging from the drive component of th= e
feedback system which is itself functioning as the inverted pendulum. In oth= er words, the axis at the top of this drive component (holding the pivot for= the usual pendulum) is of approximately the same length as the primary pend= ulum.
As the pendulum swings to the right, its axis on the drive (inverted pendulu= m) swings to the left. If the inverted pendulum were of infinite length (hor= izontal motion as was first discussed as a feedback means) all that the driv= e would accomplish is
to excite the primary pendulum via acceleration.  On the other hand, fo= r the two pendulums swinging in precise phase opposition, the net effect is=20= one of a single pendulum with a longer period.
The phase opposition of the two pendulums is guaranteed i= n the case of the folded pendulum because the two are rigidly connected.&nbs= p; Which pendulum is more effective in controlling the period depends on how= close the mass is on the horizontal connecting boom to the one pendulum or=20= the other.  Get too close to the inverted pendulum and the system goes=20= unstable (goes beyond the critical point).

Sure, but it seems to be difficult in=20= practice and you still have an extremely high tilt sensitivity.

Where my idea diff= ers from the traditional folded pendulum has to do with the 'connection' bet= ween the two pendulums.
There is no 'flexibility' of that connection in the traditional system. = ; With the feedback arrangement I've described, there is variable 'coupling'= determined by the nature of the feedback circuit's pole/zero architecture.&= nbsp; Control of the phase between the two units should be for engineers giv= en to this business 'what floats their boat'.

OK. But you will have a driven support= and a long period pendulum. What you will NOT have is the 1 second referenc= e pendulum, so I where are getting the signal to drive the support?

I see again=20= in one of Chris' statements the extreme difficulty most everyone of us has w= hen it comes to conceptual understanding of a seismometer. Yes, Newton's fir= st law says that an object at rest wants to remain at rest'.  This iner= tial property of matter is often misunderstood because not enough attention=20= is given to the part of the statement that I left off; i.e., ...remain at re= st unless acted upon by a force.

Rather my point?

Einstein sho= wed us that there doesn't have to be a force acting directly on the seismic=20= (inertial) mass. Indeed, it is the acceleration of the case that is responsi= ble for response. The mass is trying by Newton's first law to remain in plac= e as the
case is moved. But it cannot remain fixed!  As the case moves, there is= an unbalanced force on the mass that results. With the pendulum, the mass t= rying to stay at a fixed point and the case moved to a different point - mea= ns that there is a deflection of the pendulum. There is no difference to be=20= realized from this and some force applied directly to the inertial mass with= the case unmoved. Einstein's principle of relativity says that we cannot di= stinguish between the two.

My understanding of Einstein's work wo= uld not entirely support this. You are driving the case and looking at the r= elative response of the pendulum. You are not driving the pendulum. It will=20= have a lower dynamic energy.

One can think abou= t the response in the following way.  When the case moves, the inertial= mass tries to remain fixed, but it cannot remain that way ostensibly for lo= nger than 1/4th the period of the mechanical oscillator of which it is a par= t.  After
all, if the system did not oscillate, we're engaging in complete foolishness= to talk about sensitivity being proportional to the square of the natural p= eriod.

Again, one of my concerns. If you driv= e the case of a 1 Hz pendulum at 10Hz, 20 Hz you will get a direct amplitude= response. The pendulum will not be able to respond. It is the pendulum in t= he gravitational field which oscillates / fails to respond.

One can acce= ptably estimate the amount of relative motion between mass and case as follo= ws (I'm trying to avoid detailed math for those of you who are frightened by= it) Allow me just one foundational feature that you must accept on faith if= you
can't follow the math.  For an object moving at constant acceleration,=20= the distance travelled goes like the square of the time during which it acce= lerates.  Since acceleration of the inertial mass cannot be avoided as=20= the result of case movement, we see immediately that the amount of motion (i= nstrument sensitivity) is proportional to the square of the period of the in= strument.
Why, because for only about 1/4th of the period of the system can the mass b= e assumed to be moving with a 'constant' acceleration.
For those who want to believe that the inertial mass does= not accelerate (total misunderstanding of the physics of Newton's laws appl= ied to a seismometer) - think about the following. The inertial mass is inca= pable of functioning without oscillatory
motion (even though we try with critical damping to suppress the transient p= arts).  Oscillation means 'back and forth', which in turn means acceler= ation that is also back and forth oppositely directed to displacement. There= can be no displacement of the inertial mass relative to the case without a=20= corresponding acceleration of the inertial mass. It is not at rest, and neve= r can be totally at rest! To place one's emphasis on the displacement as opp= osed to the acceleration is to 'get the cart before the horse'.  Accele= ration is fundament; displacement is not!

We used to have a first year dynamics=20= demonstration apparatus. It was a horizontal glass sheet supported by four h= orizontal hinge links at the corners. On the top, there were four sprung wir= es attached around the edges. The dynamic 'pucks' were short brass cylinders= with a chamber in the top for dry ice. The dry ice (CO2) sublimated slowly=20= and provided the gas drive for the bearing on the circular base (The glass w= as polished flat and the bottom of the puck was also lapped flat.) In operat= ion, there was ~zero friction between the pucks and the glass. There was a s= tationary illuminated white perspex sheet underneath with a coarse grid rule= d on it.
In operation, you could sit two pucks o= n the glass and then move the glass in either X or Y direction and the two p= ucks stayed fixed in space relative to the grid. If no force or acceleration= is applied to the mass, it just doesn't move. To 'fire' one puck at the oth= er, you put the target one in the centre of the glass sheet, put the other o= ne up against the spring wire at one end and pushed the glass sheet. The mot= ion of the two pucks was then independent of any motion of the glass sheet u= ntil one or both bounced off the sprung wires at the edges. You could fit an= O ring to one puck to demonstrate different coefficients of restitution. Co= ld rubber doesn't bounce too well.

I suspect that you could make a fairly=20= good demonstration horizontal seismometer this way. Use a couple of small ma= gnets to provide the centralising force and detect the relative motion of th= e puck and the baseplate. If you used two pairs of magnets or bar magnets, y= ou could probably get ~single axis motion?  Or maybe a thin leaf spring= ? It should be fairly easy to get a 20 second period or longer. You could da= mp the system magnetically if you made the puck from copper or fitted a Cu d= isk to the top. Maybe use battery 'pointer' lasers and mirrors to project th= e motion onto a wall or ceiling?

How many var= iants of this discussion are necessary before folks finally GET IT (the phys= ics).  Hey, you amateurs are not the only confused ones.  Many of=20= the professional seismologists with whom I've interacted do not have a conce= ptual understanding of how a seismometer works.  It they did, they woul= dn't 'worship the god of velocity sensing'.

Don't be too hard on them. Not all seis= mologists have the physics training to design or to understand a seismometer= .. And once a particular 'system' has been adopted (for good historical reaso= ns) and thousands of seismometer years of data collected, it would take a hu= ge effort to change the system. Remember that digital recording is only mayb= e 25 years old and we are still updating older systems.
But wanting to, being able to and findi= ng useful / publishable results at periods out to 2,000 seconds could just c= hange all this. I suspect that if we are ever to be able to predict the seve= re quakes, this is the region to try to do it, where the crust is being cycl= ed by the Earth tides twice a day. That and determining the precise location= , depth and timing (or cessation) of nearby small quakes.

Regards,

Chris
Subject: Re: From: "Ted Rogers" tedr@........... Date: Tue, 19 Feb 2008 22:07:20 +1100 Chris, Do you thing that purpose could be served if the rod was a modified = "cotton reel" shape and it rolling on a polished flat plate with a = slight bow in it ? Regards Ted =20 ----- Original Message -----=20 From: ChrisAtUpw@.......... To: psn-l@................. Sent: Tuesday, February 19, 2008 5:34 PM Subject: Re:=20 In a message dated 2008/02/19, tedr@........... writes: You could create the same "rolling" effect by having 2 narrow plates = a short distance apart on the upper edge of each a shallow curve of = about 1000' radius. On these you sit a ground and polished rod of, say, = 2" (~50mm). I'm sure this would give the same effect as your cylinder, = the only problem being of course - the creation of the curves.=20 Hi Ted, You could probably get this sort of curvature most easily by = flexing a flat plate? It is approximately 0.75 thou for a 6" long plate! Part of the problem is having large area contacts. This is most = easily corrected with either strips of foil or wires. Regards, Chris Chapman
Chris,

Do you thing that purpose could be = served if the=20 rod was a modified "cotton reel" shape and it rolling on a polished = flat=20 plate with a slight bow in it ?

Regards

Ted

<tedr@...........>
----- Original Message -----
From:=20 ChrisAtUpw@.......
Sent: Tuesday, February 19, = 2008 5:34=20 PM
Subject: Re:

In a=20 message dated 2008/02/19, tedr@........... writes:

You could create the same "rolling" effect by having 2 = narrow=20 plates a short distance apart on the upper edge of each a shallow = curve of=20 about 1000' radius. On these you sit a ground and polished rod of, = say, 2"=20 (~50mm). I'm sure this would give the same effect as your cylinder, = the only=20 problem being of course - the creation of the curves. =

Hi=20 Ted,

You could probably = get this=20 sort of curvature most easily by flexing a flat plate? It is = approximately=20 0.75 thou for a 6" long = plate!

=20 Part of the problem is having large area contacts. This is most easily = corrected with either strips of foil or=20 wires.

=20 Regards,

Chris = Chapman
=20

D
o you think that purpose could= be served if the rod was a modified "cotton reel" shape and it rolling on a= polished flat plate with a slight bow in it ?

Hi Ted,

This was my idea, but I am not entirely= sure how you would go about making it.
A cylinder moving in a cylinder would w= ork in principle, but I am not sure about how you would reduce the friction=20= / link the translational and rotational motions. Need to think more carefull= y.

Regards,

Chris
Subject: Re: From: "Charles R. Patton" charles.r.patton@........ Date: Tue, 19 Feb 2008 08:39:42 -0800 Ted, Yes, that thought had occurred to me, too. One possibility would be to find a flat piece of standard window pane, mount it, and provide tension screws to physically pressure it into the desired curve. After all it is only 0.001" in 1". I think glass would bend that much. Charles Patton Ted Rogers wrote: > Charles, > > You could create the same "rolling" effect by having 2 narrow plates a > short distance apart on the upper edge of each a shallow curve of > about 1000' radius. On these you sit a ground and polished rod of, > say, 2" (~50mm). I'm sure this would give the same effect as your > cylinder, the only problem being of course - the creation of the > curves. The measurement of any movement of the rod could be done by > some sort of optical sensor looking either up or down passed a > narrower extension of the rod, or even a flat reflective surface > attached to one end of the rod... > > Regards > > Ted > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Curved strip From: ChrisAtUpw@....... Date: Tue, 19 Feb 2008 12:05:11 EST In a message dated 2008/02/19, charles.r.patton@........ writes: > One possibility would be to find a flat piece of standard window pane, > mount it, and provide tension screws to physically pressure it into the desired > curve. After all it > is only 0.001" in 1". I think glass would bend that much. Hi Charles, Much less than that. You specified a curve of 1000 ft, presumably the radius. If your strip is 6" long Center deflection = (0.25)^2 / 2000 x 12 inches = 0.000375" Regards, Chris Chapman In a me= ssage dated 2008/02/19, charles.r.patton@........ writes:

One possibility would be to fin= d a flat piece of standard window pane, mount it, and provide tension screws= to physically pressure it into the desired curve.  After all it
is only 0.001" in 1".  I think glass would bend that much.
=

Hi Charles,

Much less than that. You specified a cu= rve of 1000 ft, presumably the radius.
If your strip is 6" long
Center deflection =3D (0.25)^2 / 2000 x= 12 inches =3D 0.000375"

Regards,

Chris Chapman

The rolling foil design is the=20= one I like the best, but I would feel better
if there were more experimental results to prove it's as good as I think it=20=
will be.  see:   http://bnordgren.org/seismo/zerohng2.pdf

Hi Brett,

In the rundown tests, the rolling foil=20= performed the best. I enclosed a preference list last time I wrote to Charle= s.

> But a concurrent question=20= is do I really need a very low amount of loss?  I
>>know recent discussions have experimented with crossed pivots of ext= remely
>> low loss.  Why?  The immediate next step will be to add a= damper to get to
>> >something close to critical damping.   My understandi= ng is that the only
>> >reason to have low loss is to be able to use lots of feedback t= o lengthen
>> >the period.  But if the period can be achieved directly, a= nd it includes
>> >some damping, so what?  In my mind, the important item is<= BR> >> >hysteresis/stiction.   As bearings and bearing surfac= es can easily be
>> >ground to a ten-thousandth or even better, 10 or 20 second peri= od
>> >structures should be in reach.
>>
>        Again yes. You need to measur= e movements down to nano metres, so
> you need extremely low hysteresis / stiction -.whatever system you use.=
> Feedback will not compensate for this.

Don't agree with Chris here.  Without feedback, mechanical issues are <= BR> important, but if you have reasonably strong feedback (loop gain), which should be possible at all frequencies in the mid and low region, any
*small* effects, linear or non-linear will be made insignificant by the
feedback.

Sorry but it doesn't. This is one of the known limitation= s of feedback. It may well alter the scale.

>    &n= bsp;   Don't know where you get this from. The STS-1 used crossed=20= foils.
> The problems of making the STS-1 eventually lead to it's replacement!
See http://www.c-flex.com/technicaldata.pdf  which shows that the
crossed-foil bearings take a "set" each time they are rotated which I
consider to be a pretty good indication of significant hysteresis.  Thi= s is
consistent with the observation that the foils must undergo considerable bending stress near their points of connection with the sleeves.  I bel= ieve
that C-Flex is the successor to a series of companies which made these
bearings and am assuming that Streckeisen used either them, or something very similar in the STS-1.  Crossed foils are not necessarily low
hysteresis.  That's why I'm partial to the rolling foil design.
<= FONT COLOR=3D"#000000" BACK=3D"#ffffff" style=3D"BACKGROUND-COLOR: #ffffff"= SIZE=3D2 PTSIZE=3D10 FAMILY=3D"SANSSERIF" FACE=3D"Arial" LANG=3D"0">

This relates to C-Flex bearings. They=20= are not quite the same construction as crossed foils and I would expect ther= e to be some hysteresis. As far as I am aware, Streckeisen were making their= own flexures.

>    &nb= sp;   Let's define out objectives. We don't want extreme periods,=20= just
> maybe 10 seconds instead of 1 second. Trying to get very long periods <= BR> > makes the task increasingly difficult and the small anelastic effects <= BR> > become major problems, as do thermal variations / expansions.
>
>        I am fairly confident that yo= u could extend the period by using
> feedback to SOFTEN the suspension forces of a standard vertical pendulu= m.
> Randall can then keep his 1 mm WC low loss bearings - no problem.

Chris, can you give a bit more detail about what you're thinking here.
(block diagram or such)  Almost by definition, any significant positive=
feedback is going to oscillate.  Are you possibly thinking of using 'fe= ed
forward', sometimes called 'open loop compensation' here.  That's not <= BR> feedback but is a technique for reducing error effects, usually used to
moderately improve performance in combination with the usual negative
feedback.

Sure. Let's take the garden gate syste= m as an analogy. You alter the suspension angle to alter the centring force=20= relationship and so set the period. The centring force involved is a direct=20= function of the deflection angle for small angles. Therefore you can alter t= he period either by changing the suspension angle or by reducing the centrin= g force by force feedback. Note that force feedback can be positive or negat= ive.
If you overdo the suspension angle vari= ation, the mass falls up against the stops. If you overdo the force feedback= , the system may oscillate.

I won't say that positive feedb= ack can *never* be of use, but it has to be
combined with an even stronger dose of negative feedback in order not to oscillate, and even then you have to be careful.

The term feedforward to me indicates a=20= phase advanced signal?

Yes, one approach that h= as been used is to place a spring at the bottom to 'soften' the restoring fo= rce of gravity acting on the pendulum.  Although in principle o.k., in=20= fact it has been shown to be unacceptable, due to the dastardly properties o= f springs.

The Willmore IIIs had a period which co= uld be set from 1 to 3 seconds. The Willmore IIICs had an additional de-cent= ring spring which allowed the period to be extended to ~20 seconds. It has b= een made to work in the UK ! The alternative of providing magnetic repulsion= should be a practical possibility for the light Volksmeter suspension.

Regards,

Chris

Just because a physical pendulu= m has a long period does not mean it is useful as a seismometer! For two dec= ades I have been using such an instrument to study internal friction. The pe= riod of such a pendulum approaches very long values (easily beyond 20 s), by= causing the center of mass toget ever closer to the axis of rotation. = The way this is done, of course, is to put mass above the axis as well as b= elow it as in the simple pendulum  The long periods of oscillation are=20= possible
only for a structure that is very rigid, having a large quality factor in th= e absence of externally imposed damping.
The reason this long period pendulum is not a usefu= l seismometer is very easy to understand from the physics of extended bodies= ..  When you apply a force to an extended body, as opposed to a point ma= ss, the acceleration that results involves both translation and rotation.&nb= sp; If the force acts exactly through the center of mass, the result is stri= ctly translation; i.e., rotation is not possible because the moment arm resp= onsible for torque has vanished.
In the case of the pendulum, the acceleration of the case= is equivalent (in terms of response) to a force in the opposite direction t= o the acceleration acting directly on the pendulum through the center of mas= s. As the center of mass approaches the axis, there is no torque with which=20= to produce rotation.  Without rotation there is no response.  Thus= the instrument is not a viable seismometer, even though it is a wonderfully= useful tool for studying the influence of defect structures.

Hi Randall,

Understood.

What this de= monstrates is just one more example of the critical need to understand conce= ptually the physics involved, if one is to build a useful instrument. =20= That physics continues to be 'clouded', even by the 'analogy' you mention Ch= ris--about pucks on a table.  The demonstrations that you observed were= cases
(as appropriate to the discussion of seismic behavior) in which the frequenc= y character of disturbance was much higher than the natural frequency of the= analogous seismometer (puck/spring arrangement).  The unit was therefo= re
functioning as the 'vibrometer' that I mentioned earlier.

My fault. I had not picked up that you were referring to=20= a seismometer when the excitation frequency was below resonance, but were ca= lling it a vibrometer when the excitation frequency was above resonance.

The vibrometer works on the basis
of the fact (low eignfrequency of the instrument compared to frequency o= f acceleration disturbance) that there is insignifcant motion of the mass (p= uck) over the time intervals of external (case) disturbance.  This is n= ot the regime for which are trying so hard to improve instrument performance= ..

OK

That regime is at the opposite= end of the excitation frequency spectrum.  When the case of a seismome= ter is accelerated at very low frequencies of the earth's motion, there is a= bsolutely no way one can think of the inertial mass remaining at rest! The m= ass is connected to something (whether spring or pendulum rod) that serves a= s
a device to keep it centered in the case and which is responsible for the se= ismometer being a mechanical oscillator.  If it were not an oscillator,= then there would be no reason to provide eddy current dampers using rare ea= rth magnets.  Simply stated, the inertial mass MUST be part of an oscil= lator IF it is to be a seismometer.  If it oscillates, then the mass ca= nnot remain at rest, and there is a repeat interval of time associated with=20= the motion, called the period of oscillation.  The finite value of this= period is what in turn causes an upper limit on the sensitivity that is gov= erned by the square of the period of oscillation. The reason there is a limi= t to the amount of relative motion between mass and case (instrument sensiti= vity) is the FACT that the inertial mass DOES move. There is ABSOLUTELY no w= ay it CANNOT!

Agreed.

On a differe= nt subject:

Chris you mention what I believ= e to be indeed true - publishable results out to (and beyond) 2000 s could c= hange a great deal in the world of seismology. It is a virtually unexplored=20= regime. Let me give you an example. I was just yesterday looking at the diff= erences between the N-S and E-W channels of my VolksMeter here in Macon. Bec= ause the concrete cylinder that is part of the monolithic pier goes 20 ft in= to the ground, there is a significant reduction in the thermoelastic tilt th= at is otherwise seen for instruments sitting on a slab on top of the earth.&= nbsp; What is really interesting about the two channel records, for 1 sample= per minute over 24 h is the following.  Sometimes the two channels are= almost completely correlated.  Whatever is tilting the pier is the sam= e in both N-S and E-W direction.
But there are days in which this is not at all true. = ; A correlation plot shows fascinating loop-the-loops that seem to cycle ove= r a period of several days.  Is this something local to middle Georgia,= or does it have global features?  The answer to this important questio= n can only be provided by networked sensors.  What I find remarkable is= that a simple pendulum has the potential to do some experiments which cry o= ut for data collection.  Anybody who believes that science is in the process of just 'tying up loose ends' to mature understand of nature (whethe= r in physics or any other discipline) is hopelessly naive.  It is mind=20= boggling to me the extent to which seismology has only 'scratched the surfac= e' with regard to a true
understanding of earth's complex motions. One of the reasons so little under= standing has been gained derives from the 'delta function' mentality concern= ing sensor type for instruments.

Interesting.

Which was why I suggested siting an ins= trument at Eskdalemuir 55.3N 3.2W in the UK, about 81 degrees E from Macon 3= 2.85N -83.68W, or at Walferdange 49.7N 6.2E in Luxembourgh at about 89 degre= es E? Eskdalemuir is a good bit further N than Macon.

But we still have to motivate the seism= ologists and get the long period equipment to them. STS-1s are in short supp= ly and STS-2s and Guralp CMG 3T can be ordered in 360 sec version, but the T= rillium is limited to 240 seconds. They are all a bit short on period for Ea= rth Eigenmodes. I haven't checked the noise levels. The Scripps Institute se= ems to be junking their STS-1s??

I suspect that Volksmeters could well m= ake excellent Tsunami detectors, particularly off the west coast of the Amer= icas where the major faults are less than 500 miles offshore and the warning= response times need to be just a few minutes.They could pick up the tilt si= gnals from vertical ocean floor changes directly.  I am not sure about=20= the likely deflection amplitudes required?
I have just been watching a TV program=20= about the Cascadia fault off Canada + USA. They were suggesting movement on=20= the coast of up to a foot and a M 9 quake about 600 miles long. The last qua= ke was in 1700 and the previous one was about 300 years before that. This so= unds too close for comfort.
Subject: Nevada earthquake From: jonfr@......... Date: Thu, 21 Feb 2008 09:54:11 -0500 (EST) Hi all According to EMSC there was a Mw6.3 earthquake in Nevada at 14:16 GMT. I guess that there is an damaged following this event. I don't know yet if my station did record it. Regards. Jón Frímann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Nevada earthquake<<< UT From: "Jim ODonnell" geophysics@.......... Date: Thu, 21 Feb 2008 15:31:06 GMT Probably Not- Not too many folks live in the area- closer to Salt Lake C= ity but still to far away...My jugs are still ringing tho<<<<,Jim Jim O'Donnell = Geological/Geophysical Consultant GEOTECHNICAL APPLICATIONS 702.293.5664 geophysics@.......... 702.281.9081 cell jimo17@........ -- jonfr@......... wrote: Hi all According to EMSC there was a Mw6.3 earthquake in Nevada at 14:16 GMT. I= guess that there is an damaged following this event. I don't know yet if my station did record it. Regards. J=C3=B3n Fr=C3­mann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) See http://www.seismicnet.com/maillist.html for more information. Probably Not- Not too many folks live in the area- closer to Salt = Lake City but still to far away...My jugs are still ringing tho<<&= lt;<,Jim

&= nbsp;         Jim O'Donnell=
&= nbsp;Geological/Geophysical Consultant
=       GEOTECHNICAL APPLICATIONS
702.293= ..5664    geophysics@..........
702.281.9081 cell  = ; jimo17@........

-- jonfr@......... wrote:
Hi all
According to EMSC there was a Mw6.3 earthquake in Nevada at 14:16 GMT. = I
guess that there is an damaged following this event.

I don't= know yet if my station did record it.

Regards.
J=C3=B3n Fr=C3= ­mann.
__________________________________________________________=

Public Seismic Network Mailing List (PSN-L)

To leave this= list email PSN-L-REQUEST@.............. with
the body of the messag= e (first line only): unsubscribe
See http://www.seismicnet.com/mailli= st.html for more information. Subject: Re: Nevada earthquake<<< UT From: "Jerry Payton" gpayton880@....... Date: Thu, 21 Feb 2008 09:52:43 -0600 FOX NEWS is reporting scattered reports of damages: collapsed building, cracks and goods shaking on shelves in surrounding states. On site reports have been slow in coming and not been shown yet. Jerry ----- Original Message ----- From: Jim ODonnell To: psn-l@.............. Sent: Thursday, February 21, 2008 9:31 AM Subject: Re: Nevada earthquake<<< UT Probably Not- Not too many folks live in the area- closer to Salt Lake City but still to far away...My jugs are still ringing tho<<<<,Jim Jim O'Donnell Geological/Geophysical Consultant GEOTECHNICAL APPLICATIONS 702.293.5664 geophysics@.......... 702.281.9081 cell jimo17@........ -- jonfr@......... wrote: Hi all According to EMSC there was a Mw6.3 earthquake in Nevada at 14:16 GMT. I guess that there is an damaged following this event. I don't know yet if my station did record it. Regards. JĂłn FrĂ­mann. __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
FOX NEWS is reporting scattered reports of damages: collapsed = building,=20 cracks and goods shaking on shelves in surrounding states.  On site = reports=20 have been slow in coming and not been shown yet.
Jerry

----- Original Message -----=20
From: Jim = ODonnell=20
Sent: Thursday, February 21, 2008 9:31 AM

Probably Not- Not too many folks live in the area- closer = to Salt=20 Lake City but still to far away...My jugs are still ringing=20 tho<<<<,Jim

&n= bsp;           Jim= =20 O'Donnell=20
&nb= sp;Geological/Geophysical=20 Consultant
= ; GEOTECHNICAL=20 APPLICATIONS
702.293.5664    geophysics@..........
702.28= 1.9081=20 cell   jimo17@........

--=20 jonfr@......... wrote:
Hi=20 all

According to EMSC there was a Mw6.3 earthquake in Nevada at = 14:16=20 GMT. I
guess that there is an damaged following this event.

I = don't=20 know yet if my station did record it.

Regards.
J=C3=B3n=20 Fr=C3­mann.
______________________________________________________= ____

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

To leave this list email=20 PSN-L-REQUEST@.............. with
the body of the message (first = line only):=20 unsubscribe
See http://www.seismicnet.com/maillist.html for more = information.=20 Subject: 6.0M Nevada From: tchannel1@............ Date: Thu, 21 Feb 2008 12:57:05 -0700 Hi Folks, Things very busy here today. No local damage of course, but I = did feel IT. I was still in bed but awake and thinking I should be = getting up. I felt the room move? I thought it was the wind, and heard a small = noise. I noted the clock at 7:17am our time. We have recently installed a vertical spring sensor at River Glen Jr. = High School which shares the building with the TVMSC Treasure Valley = Math and Science Center. The sensor is on the second floor of a three story building. In two = weeks the school has recorded 7 earthquakes. One of which was 9000 miles = away.=20 They certainly got this one, all the 8th Grader where thrilled. Their = event is posted on PSN as TVMSC Boise Id. Two News station did an on = site interview at the school. Channel 2 and 7. I also recorded in at TCID using my new (Larry's) three channel = Amp/filter. I took a screen shot of the Helicorder and it is very interesting on = it's own. E'mail me and I can send it to you as a .jpg. It's a keeper. Alls-Well here in Boise. Damage reported in Nevada but I have heard of = no injuries. One call to the TV station reported it threw a cat out of a chair..... Cheers Ted

Hi Folks, Things very busy here today. No local damage of course, but = I did=20 feel IT. I was still in bed but awake and thinking I should be getting = up.

I felt the room move? I thought it was the wind, and heard a small = noise. I=20 noted the clock at 7:17am our time.

We have recently installed a vertical spring sensor at River Glen Jr. = High=20 School which shares the building with the TVMSC Treasure Valley Math and = Science=20 Center.

The sensor is on the second floor of a three story building. In two = weeks the=20 school has recorded 7 earthquakes. One of which was 9000 miles away. =

They certainly got this one, all the 8th Grader where = thrilled.=20 Their event is posted on PSN as TVMSC Boise Id. Two News station did an = on site=20 interview at the school.

Channel 2 and 7.

I also recorded in at TCID using my new (Larry=92s) three channel=20 Amp/filter.

I took a screen shot of the Helicorder and it is very interesting on = it=92s=20 own.

E=92mail me and I can send it to you as a .jpg. It=92s a keeper.

Alls-Well here in Boise. Damage reported in Nevada but I have heard = of no=20 injuries.

One call to the TV station reported it threw a cat out of a = chair=85=85=85..

Cheers

Ted

Hi Folks,  We have been recording = many=20 aftershocks following the 6.0M Nevada Feb. 21st.  Several in the = 4's and=20 many more 3's.
I have not been counting the 3's but = around 6=20 events in 24 hours?   I just looked a the last three events = from this=20 area, 3.2M, 3.1M, and 3.2M in the last few hours.
These are about 160 miles or 310km, and = the 3's are=20 coming through very well defined.  If these were not so = numerous I=20 would be posting each and every one.

With my equipment I rarely record = events this small=20 and this numerous.   Too many earthquakes to process=20 !
If I were to process all the ones = I am=20 recording from this area, I would be processing 24hours a = day.

I am recording with two different = sensors. =20 One is a Slinky II, which works very well, but even better , the latest=20 one,   I am calling a Tilt Meter, which is a very simple 2 = second=20 pendulum, hanging down like a Grandfather Clock.  It contains a = nice coil,=20 4000 turns and 4 magnets, nice, but nothing complex.
At any rate this machine is working = better than any=20 of my other 10 efforts.

If someone is serious about building an = inexpensive, but effective sensor, contact me and I will share my = pictures and=20 design notes.   I think the reason it is working so well is = the=20 special coil and the fact that it uses a simple tilt.   I am = posting=20 these as TCIDTM.

Meanwhile,  The school, TVMSC is = recording=20 away, using the small copper vertical sensor, and it is working well for = them.   They also are recording many of the 3's=20 aftershock.    They sure were happy to see the = 6.0M  =20 The school had two TV channels come out and interview the 8th=20 graders.   I was there and and sure was smiling.   = The=20 reporters ask several of the kids if they felt it, and each told an=20 account.   One boy, said "Well there I was, just eating my = oatmeal,=20 and I felt the table shake"    Another one said "It = knotted my=20 cat out of the chair"

Perhaps I could get some of the kids to = write their=20 experience, and post them here?    I will ask their = teacher Ms.=20 Poppenga.

Cheers
Ted
Subject: Re: Many Nevada aftershock From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@......... Date: Sat, 23 Feb 2008 15:10:43 +0000 Hi Do you have any numbers of how many aftershocks you are recording ? By my standards anything less then 100 isn't many. When I get a big earthquake swarm it can take me several weeks to review all the earthquakes. 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: Many Nevada aftershock From: tchannel1@............ Date: Sat, 23 Feb 2008 08:20:11 -0700 Hi Jon, No I don't have numbers. I am sure they are fewer than you are seeing in your part of the world. However this is the first time for me, being close enough to an earthquake to see small aftershocks..........all very interesting. Ted ----- Original Message ----- From: "Jón Frímann" To: Sent: Saturday, February 23, 2008 8:10 AM Subject: Re: Many Nevada aftershock Hi Do you have any numbers of how many aftershocks you are recording ? By my standards anything less then 100 isn't many. When I get a big earthquake swarm it can take me several weeks to review all the earthquakes. 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: Many Nevada aftershock<<< wrote: Hi Jon, No I don't have numbers. I am sure they are fewer than you ar= e = seeing in your part of the world. However this is the first time for m= e, = being close enough to an earthquake to see small aftershocks..........al= l = very interesting. Ted ----- Original Message ----- = From: "J=F3n Fr=EDmann" To: Sent: Saturday, February 23, 2008 8:10 AM Subject: Re: Many Nevada aftershock Hi Do you have any numbers of how many aftershocks you are recording ? By my standards anything less then 100 isn't many. When I get a big earthquake swarm it can take me several weeks to review all the earthquakes. Regards. -- = 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) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) See http://www.seismicnet.com/maillist.html for more information.

Try UNR seismograph station- Great map of aftershocks.
= Wells ~500 miles north of Las Vegas where I am.....Jim

http://www.seismo.unr.edu/=

=         Jim O'Donnell  &nbs= p;
Geolog= ical/Geophysical Consultant
= ;    GEOTECHNICAL APPLICATIONS
702.293.5664  = ;  geophysics@..........
702.281.9081 cell   jimo= 17@........

-- <tchannel1@............> wrote:
Hi Jon, &= nbsp; No I don't have numbers.  I am sure they are fewer than = you are
seeing in your part of the world.   However this i= s the first time for me,
being close enough to an earthquake to see = small aftershocks..........all
very interesting.
Ted
----- Ori= ginal Message -----
From: "J=F3n Fr=EDmann" <jonfr@.........><= BR>To: <psn-l@..............>
Sent: Saturday, February 23, 2008= 8:10 AM

Hi

Do = you have any numbers of how many aftershocks you are recording ?

= By my standards anything less then 100 isn't many. When I get a big
e= arthquake swarm it can take me several weeks to review all the
earthq= uakes.

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

____________________________________________= ______________

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To leave this list email PSN-L-REQUEST@.............. with
the body = of the message (first line only): unsubscribe

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Subject: Re: Many Nevada aftershock<<< wrote: Hi Jon, No I don't have numbers. I am sure they are fewer than you = are=20 seeing in your part of the world. However this is the first time for = me,=20 being close enough to an earthquake to see small = aftershocks..........all=20 very interesting. Ted ----- Original Message -----=20 From: "J=F3n Fr=EDmann" To: Sent: Saturday, February 23, 2008 8:10 AM Subject: Re: Many Nevada aftershock Hi Do you have any numbers of how many aftershocks you are recording ? By my standards anything less then 100 isn't many. When I get a big earthquake swarm it can take me several weeks to review all the earthquakes. 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) 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) To leave this list email PSN-L-REQUEST@.............. with=20 the body of the message (first line only): unsubscribe See http://www.seismicnet.com/maillist.html for more information.
Hi Jim,  Thanks, nice = site.
Ted
----- Original Message -----
From:=20 Jim=20 ODonnell
Sent: Saturday, February 23, = 2008 8:39=20 AM
Subject: Re: Many Nevada=20 aftershock<<<<Map of aftershocks

Try UNR seismograph station- Great map of = aftershocks.
Wells ~500=20 miles north of Las Vegas where I am.....Jim

http://www.seismo.unr.edu/

&n= bsp;      Jim=20 O'Donnell=20 =
&nb= sp;Geological/Geophysical=20 = Consultant
= ; GEOTECHNICAL=20 APPLICATIONS
702.293.5664    geophysics@..........
702.28= 1.9081=20 cell   jimo17@........

-- <tchannel1@............>=20 wrote:
Hi Jon,   No I don't have numbers.  I am sure = they=20 are fewer than you are
seeing in your part of the world.=20   However this is the first time for me,
being close = enough to=20 an earthquake to see small aftershocks..........all
very=20 interesting.
Ted
----- Original Message -----
From: "J=F3n = Fr=EDmann"=20 <jonfr@.........>
To: <psn-l@..............>
Sent: = Saturday,=20 February 23, 2008 8:10 AM

Hi

Do you have any numbers of how many=20 aftershocks you are recording ?

By my standards anything less = then 100=20 isn't many. When I get a big
earthquake swarm it can take me = several weeks=20 to review all the
earthquakes.

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

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

To leave this list email=20 PSN-L-REQUEST@.............. with
the body of the message (first = line=20 only): unsubscribe
See http://www.seismicnet.com/maillist.html for = more=20 = information.

_____________________________________________________= _____

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

To leave this list email=20 PSN-L-REQUEST@.............. with
the body of the message (first = line=20 only): unsubscribe
See http://www.seismicnet.com/maillist.html for = more=20 information.

Subject: Long Period Pendulums From: tchannel1@............ Date: Sat, 23 Feb 2008 10:29:12 -0700 Hi Folks, http://www.phy.mtu.edu/~suits/PH3110/pendulums.html This is = a description of different long period pendulums. My goal in building = sensors is to obtain the long period, like 20 seconds, In most cases I = have found this hard to do. I know it can be done, but even with the = Lehman the setup to get to 20 second is, for me difficult. I usually = give up at about 15 seconds. I was pointed to this wed site long ago, and tried my hand at some of = the ideas. I made some prototypes, spending very little time, and had = little success. After thinking about the "Rocking Chair Pendulum" recently discussed, I = saw a similarity between it and one of these Long period pendulums, so I = went back to the shop and made another mock up of the "Nearly Balanced = Pendulum" This time I took a little more time. Using a 48" dowel, I = drilled a pivot hole in the center, inserted a finishing nail into the = pivot hole, attached the nail to a table top, so the dowel would spin = like a propeller. Next I threaded a 1/2" machine bolt, nut onto one = end of the dowel. I timed the period at 2.5 seconds. I threaded = another nut on to the opposite end of the dowel, this time one half the = distance, from the end to the pivot. I timed the period at about 3.5 = seconds. I keep moving the second nut closer to the end of dowel, to = match the first nut which remained at the opposite end of the dowel. = As I move the nut the period got longer and longer. When I reached the = end of the dowel, I got a 20 second period, with very little effort. All this may be old news to some of you, but I found it to be amassing. = Now I need to build another sensor, using this approach. I think I will do another mock up, this time taking great care as to the = pivot and finer adjustments, to see how long a period I can achieve. Thanks, Ted
Hi Folks,  http://www.p= hy.mtu.edu/~suits/PH3110/pendulums.html =20 This is a description of different long period pendulums.   My = goal in=20 building sensors is to obtain the long period, like 20 seconds,  In = most=20 cases I have found this hard to do.   I know it can be done, = but even=20 with the Lehman the setup to get to 20 second is, for me = difficult.  =20 I usually give up at about 15 seconds.

I was pointed to this wed site long = ago, and tried=20 my hand at some of the ideas.   I made some prototypes, = spending very=20 little time, and had little success.
After thinking about the "Rocking Chair = Pendulum"=20 recently discussed, I saw a similarity between it and one of these = Long=20 period pendulums, so I went back to the shop and made another mock up of = the=20 "Nearly Balanced Pendulum"    This time I took a little = more=20 time.  Using a 48" dowel, I drilled a pivot hole in the center, = inserted a=20 finishing nail into the pivot hole, attached the nail to a table top, so = the=20 dowel would spin like a propeller.   Next I threaded a 1/2" = machine=20 bolt, nut onto one end of the dowel.   I timed the period at = 2.5=20 seconds.   I threaded another nut on to the opposite end of = the dowel,=20 this time  one half the distance, from the end to the = pivot.   I=20 timed the period at about 3.5 seconds.   I keep moving the = second nut=20 closer to the end of dowel, to match the first nut which remained at the = opposite end of the  dowel.   As I move the nut the = period got=20 longer and longer.  When I reached the end of the dowel, I got a 20 = second=20 period, with very little effort.

All this may be old news to some of = you, but I=20 found it to be amassing.   Now I need to build another sensor, = using=20 this approach.

I think I will do another mock up, this = time taking=20 great care as to the pivot and finer adjustments, to see how long a = period I can=20 achieve.

Thanks,
Ted
Subject: Re: Many Nevada aftershock From: John Lahr johnjan@........ Date: Sat, 23 Feb 2008 11:24:06 -0800 J=F3n, The larger events are listed here: http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/US2/40.42.-115.-113_eqs= ..php Looks like many small events are not included. John At 07:10 AM 2/23/2008, you wrote: >Hi > >Do you have any numbers of how many aftershocks you are recording ? > >By my standards anything less then 100 isn't many. When I get a big >earthquake swarm it can take me several weeks to review all the >earthquakes. > >Regards. >-- >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) > >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: Long Period Pendulum From: tchannel1@............ Date: Sat, 23 Feb 2008 13:38:03 -0700 Hi Folks, I set up another test in the shop for the "Nearly Balanced = Pendulum" This time I found I could only get about 15 seconds, using a = 48" dowel with a center pivot at 24". Here is what I found: As I moved the top mass closer to the end of the dowel, which countered = the fixed lower mass, the dowel's balance point would start to move from = vertical to horizontal. With no mass on the top, the dowel was vertical, because of the lower = mass. Placing the top mass at about half way up, the top half of the = 48" dowel, the whole thing still remained vertical. As I moved the top = mass higher, the dowel started to favor a 45 degree balance point, and a = longer period, about 6 seconds. The higher I moved the top mass, the longer the period, but now the = balance point was getting close to horizontal. I maxed out at 15 seconds, and the dowel nearly horizontal. If I used = a longer dowel I guess I would get a longer period. Q. 1. This movement from vertical to horizontal, it this expected? or = should it remain vertical as the period get longer? Q 2. Should I get more than 15 seconds, by using finer adjustment of = the top mass? I would think infinite. My goal here, is to keep the dowel vertical, so if I swing it, it will = return to vertical, yet obtain the longest period. With this = experiment, I can keep it vertical, but only achieve less than 10 = seconds period. Of course I want to use the shortest possible, = pendulum, say 48" Not sure if it is my set up, or perhaps my adjustments are still too = coarse, or if this movement from vertical to horizontal is normal. Thanks, Ted
Hi Folks,   I set up another = test in the=20 shop for the "Nearly Balanced Pendulum"   This time I = found I=20 could only get about 15 seconds, using a 48" dowel with a center pivot = at=20 24".   Here is what I found:

As I moved the top mass closer to the = end of the=20 dowel, which countered the fixed lower mass, the dowel's balance=20 point would start to move from vertical to horizontal.

With no mass on the top, the dowel was = vertical,=20 because of the lower mass.   Placing the top mass at about = half way=20 up, the top half of the 48" dowel, the whole thing still remained=20 vertical.  As I moved the top mass higher, the dowel started to = favor a 45=20 degree balance point, and a longer period, about 6 seconds.
The higher I moved the top mass, the = longer the=20 period, but now the balance point was getting close to = horizontal.

I maxed out at 15 seconds, and the = dowel nearly=20 horizontal.   If I used a longer dowel I guess I would get a = longer=20 period.

Q.  1.  This movement from = vertical to=20 horizontal, it this expected?  or should it remain vertical as the = period=20 get longer?
Q   2.  Should I get = more than 15=20 seconds, by using finer adjustment of the top mass?  I would think=20 infinite.

My goal here, is to keep the dowel = vertical, so if=20 I swing it, it will return to vertical, yet obtain the longest = period. =20 With this experiment, I can keep it vertical, but only achieve less than = 10=20 seconds period.   Of course I want to use the shortest = possible,=20 pendulum, say 48"

Not sure if it is my set up, or perhaps = my=20 adjustments are still too coarse, or if this movement from vertical to=20 horizontal is normal.

Thanks, Ted