Subject: Re: all the best for the new year From: ian ian@........... Date: Fri, 31 Dec 2004 20:23:27 +0000 Happy New Year too. The USGS said on the day of the disaster that they were aware of the in coming tsunamis before they hit but didn't know who to contact. So the problem is not one of detection - the usgs have that covered - but one of dissemination. There is no communication and warning network around the affected area. I've heard that they had considered one but nothing happened. I guess there will soon be one now. Here, needless to say, my detector was off at the time, so unfortunately I missed an important test of my new Lehman. Ian Smith Mark Robinson wrote: > Hi everybody, > > The phrase "rock my world" just went out of fashion. > > I wonder if there is any software about that can monitor a seismograph > signal, pick P and S arrivals, calculate magnitude, location, tsunami > threat level, tsunami time of arrival over a defined coastline map, > automatically consult and vote with other neighbouring stations on the > threat level, and flip a bit on a serial or parallel port if > everything is looking really ugly, perhaps morse code "TS" ? You know, > all the bells and whistles. > > My coding skills suck these days, but I'll contribute whatever I can > to such a project if it doesn't exist, and if anyone else wants to, > purely in my own interests, living as I do on seaside sand dunes on an > active part of the intersection of the pacific and australien plates. > > Enjoy your friendships in celebrating the New Year. > Mark Robinson > ------------- > 01 Jan 1853 The strongest known earthquake in the New Plymouth area. 6.5. > 01 Jan 1854 Sir James George Frazer, author and scholar, born. > 01 Jan 1867 First Chinese immigrants to NZ arrive at Hokitika. > 01 Jan 1897 Author E M Forster born. > 01 Jan 1950 Castro seizes power in Cuba, Batista flees. > 01 Jan 1984 Mimiwhangata Marine Park established. > 01 Jan 1991 Presidents Bush and Gorbachev condemn Iraqi conquest of > Kuwait in > New Year's messages. > > > There's a mainframe wrecker about 70km from here that sells > semiconductor relays for $NZ3 each. These are easy to drive off a port > pin. > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: all the best for the new year From: Mark Robinson mark.robinson@............... Date: Sat, 01 Jan 2005 13:49:37 +1300 ian wrote: > Happy New Year too. > > The USGS said on the day of the disaster that they were aware of the in > coming tsunamis before they hit but didn't know who to contact. So the > problem is not one of detection - the usgs have that covered - but one > of dissemination. Hi Ian, Agreed, the problem is dissemination and communication, and the top down structure which is constrained by diplomatic protocols is too slow to be affective for many people, including me, for local events. Devices such as those I propose could mitigate these delays and save many many lives in similar future events. For me, safety from a large tsunami is a 7 minute drive on empty roads, or an hour walking and running. The local fire siren going off withing a minute or so of the initiating tremblor could reduce the radius without warning immensely, especially compared to people working their way through a documented protocol with a telephone. Let alone the political ramifications for many states who do not enjoy good political relations with the USA. We have already seen the USGS public face restricted for strategic reasons in the aftermath of 11Sep2001. I note that Indonesia now expects their death toll to be in the vicinity of 400,000. http://www.bernama.com/bernama/v3/news_lite.php?id=111574 "KUALA LUMPUR, Dec 30 (Bernama) -- The death toll in Acheh, the region worst hit by last Sunday's tsunami, may exceed 400,000 as many affected areas could still not be reached for search and rescue operations, Indonesia's Ambassador to Malaysia Drs H. Rusdihardjo said Thursday. He said the estimate was based on air surveillance by Indonesian authorities who found no signs of life in places like Meulaboh, Pulau Simeulue and Tapak Tuan while several islands off the west coast of Sumatera had "disappeared". He said the latest death toll of more than 40,000 in Acheh and northern Sumatera did not take into account the figures from the other areas, especially in the west of the region. ...." regards all Mark __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: P & S Markers Location, WQ From: "Steve Jones" acme100@.............. Date: Sun, 2 Jan 2005 19:39:06 -0600 Hi Larry, I have a question re: Winquake, and the P&S Marker location. I recorded the 12/26/04 M9.0 event (along with everybody else) and the later 01/01/05 M6.5 event off Sumatra. On both of these, I cannot get the P & S marker locations on the record to align with the first arrival of the P and S waves at my location. For each event, Winquake does calculate the distance to my location from the epicenter at 15000+ Km. I am running the WQ version 2.9, if that info helps. I have very carefully checked my timing and event location data plugged into Winquake. Do you have any idea why the P & S calculation seems to be off? If need be, I can email the two event records to you for your examination. Thanks, Steve Jones Huntsville, Alabama __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: P & S Markers Location, WQ From: apsn apsn@........... Date: Sun, 02 Jan 2005 16:55:39 -0900 Steve, Check your TABLES menu and make sure that you use either the IASPEI or Teleseismic tables. Bob http://apsn.awcable.com At 04:39 PM 1/2/2005, you wrote: >Hi Larry, >I have a question re: Winquake, and the P&S Marker location. I recorded the >12/26/04 M9.0 event (along with everybody else) and the later 01/01/05 M6.5 >event off Sumatra. On both of these, I cannot get the P & S marker >locations on the record to align with the first arrival of the P and S waves >at my location. For each event, Winquake does calculate the distance to my >location from the epicenter at 15000+ Km. > >I am running the WQ version 2.9, if that info helps. I have very carefully >checked my timing and event location data plugged into Winquake. Do you >have any idea why the P & S calculation seems to be off? > >If need be, I can email the two event records to you for your examination. > >Thanks, >Steve Jones >Huntsville, Alabama > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: P & S Markers Location, WQ From: "Larry Cochrane" lcochrane@.............. Date: Sun, 2 Jan 2005 20:09:26 -0800 Happy New Year Everyone, Hi Steve, You won't see a P or S wave after ~11000 km. This is because the earths core creates a shadow of the P wave and the outer core a shadow of the S wave. If you do a google search you can find more information. This page as a nice image showing what going on with the P and S waves. The IAPS91 travel-time table has information that goes past 11000km so WinQuake will place the P and S marks in the window, but they are meaningless do to the shadowing effect. Regards, Larry Cochrane Redwood City, PSN ----- Original Message ----- From: "Steve Jones" To: Sent: Sunday, January 02, 2005 5:39 PM Subject: P & S Markers Location, WQ > Hi Larry, > I have a question re: Winquake, and the P&S Marker location. I recorded the > 12/26/04 M9.0 event (along with everybody else) and the later 01/01/05 M6.5 > event off Sumatra. On both of these, I cannot get the P & S marker > locations on the record to align with the first arrival of the P and S waves > at my location. For each event, Winquake does calculate the distance to my > location from the epicenter at 15000+ Km. > > I am running the WQ version 2.9, if that info helps. I have very carefully > checked my timing and event location data plugged into Winquake. Do you > have any idea why the P & S calculation seems to be off? > > If need be, I can email the two event records to you for your examination. > > Thanks, > Steve Jones > Huntsville, Alabama > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: P & S Markers Location, WQ From: John or Jan Lahr JohnJan@........ Date: Sun, 02 Jan 2005 22:37:36 -0700 Hi Steve,

You can use the calculator on this page:
http://neic.usgs.gov/neis/travel_times/artim.html
to find the time of arrival of all of the phases at your station. 

Cheers,
John

\At 09:09 PM 1/2/2005, you wrote:
Happy New Year Everyone,

Hi Steve,

You won't see a P or S wave after ~11000 km. This is because the earths core
creates a shadow of the P wave and the outer core a shadow of the S wave. If
you do a google search you can find more information. This page as a nice
image showing what going on with the P and S waves. The IAPS91 travel-time
table has information that goes past 11000km so WinQuake will place the P
and S marks in the window, but they are meaningless do to the shadowing
effect.

Regards,
Larry Cochrane
Redwood City, PSN


##################################/ John C. Lahr
#################################/ Emeritus Seismologist
################################/ U.S. Geological Survey
===========================/ Geologic Hazards Team, MS966
##############################/ PO Box 25046
#############################//##############################
############################//###############################
     Denver, Colorado 80225-0046 /################################
             Phone: (303) 215-9913 /=============================
               Fax: (303) 273-8540 /##################################
                     lahr@........ /###################################
                                          /####################################
                                 http://jclahr.com/science/
 Subject: Accelerometer on ebay From: "Edward Ianni" edwianni1@........... Date: Mon, 3 Jan 2005 21:29:39 -0500 Accelerometer ebay 3864167120 Ed Ianni

Accelerometer        &nb= sp; ebay=20 3864167120
 
Ed Ianni
Subject: Re; Accelerometers From: "Edward Ianni" edwianni1@........... Date: Tue, 4 Jan 2005 00:14:57 -0500 The link below may be useful in reference to accelerometers. The message is ready to be sent with the following file or link = attachments: Shortcut to: = http://www.civil.canterbury.ac.nz/eq/cusp1_04presentation.pdf =20 Ed Ianni
The link below may be useful in = reference to=20 accelerometers.
 
The=20 message is ready to be sent with the following file or link=20 attachments:
Shortcut to: http://www.civil.canterbury.ac.nz/eq/cusp1_04presentation.pdf
 
Ed = Ianni
Subject: Re: Accelerometer on ebay From: BOB BARNS royb1@........... Date: Tue, 04 Jan 2005 09:58:57 -0500 Hi Ed, This is a 3-pen chart recorder only, I think. It would prob. take 1V signals from seismic sensors for full scale. It would be hard to find chart paper and ink. Chart recording has gone out of style since computers can do so much more. OK on the accelerometer article. Bob Edward Ianni wrote: > Accelerometer ebay 3864167120 > > Ed Ianni > > > __________ NOD32 1.963 (20050103) Information __________ > > This message was checked by NOD32 antivirus system. > http://www.nod32.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: looking for a seismograph From: "David Saum" DSaum@............ Date: Tue, 4 Jan 2005 11:31:17 -0500 I received this message today and it is not something I know anything about. I hope there is someone on the list who can answer this question. -- Dave ----- Original Message ----- From: To: Sent: Tuesday, January 04, 2005 2:44 AM Subject: looking for a seismograph Dear Collegues, Your ewb infiltec.com is very interesting for me. I am looking for a seismograph equipment I hope You may help me to fine dealer and spec of equipment. I will be much appreciate if you could directs me to a dealer. I am looking for Drum type earthquake recorder which capable for detect quake from long distant i,e, should not be a strong motion equipment. Best regards Tun Aye __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: looking for a seismograph From: John or Jan Lahr JohnJan@........ Date: Tue, 04 Jan 2005 10:41:25 -0700 Dear Tun Aye,

Today very few seismic stations are recorded on a drum recorder.  The
expense of the drum and paper, combined with the daily chore of
changing the paper make this technique much less desirable than
recording digitally with a PC computer.  Also, with digital recording
one can adjust the time and amplitude scales as well as the filter
settings after an earthquake has been recorded.  This is especially 
helpful  in making measurements.

One option that is quite easy to set up would be to purchase an
AS1 instrument for $550.00.  In addition to the instrument you would
need a PC computer running MSWindows and the free software
AmaSeis, which can be downloaded from the web.

There is information on this approach posted here:
http://jclahr.com/science/psn/as1/

Some current records from schools are posted here:
http://jclahr.com/science/psn/as1/heli/allas1.php

Records of the recent M 9.0 Sumatra event are here:
http://jclahr.com/science/psn/as1/indonesia04/as1indo.html

*****
On the other hand, if you want to build your own system, there
is lots of information on the PSN web site:
http://psn.quake.net/

and here:
http://jclahr.com/science/psn/epics/links.html

Best of luck with your seismic recording.
John

At 09:31 AM 1/4/2005, you wrote:
I received this message today
and it is not something I know
anything about.
I hope there is someone
on the list who can answer
this question.  -- Dave

----- Original Message -----
From: <info-dmh@..........>
To: <dsaum@............>
Sent: Tuesday, January 04, 2005 2:44 AM
Subject: looking for a seismograph


Dear Collegues,

Your ewb infiltec.com is very interesting
for me.
I am looking for a seismograph equipment
I hope You may help me to fine
dealer and spec of equipment.

I will be much appreciate if you
could directs me  to a dealer.

I am looking for
 Drum type earthquake recorder
     which capable for detect quake from long distant
     i,e, should not be a strong motion equipment.

Best regards

Tun Aye
__________________________________________________________

Public Seismic Network Mailing List (PSN-L)

http://www.seismicnet.com/maillist.html for more information.


##################################/ John C. Lahr
#################################/ Emeritus Seismologist
################################/ U.S. Geological Survey
===========================/ Geologic Hazards Team, MS966
##############################/ PO Box 25046
#############################//##############################
############################//###############################
     Denver, Colorado 80225-0046 /################################
             Phone: (303) 215-9913 /=============================
               Fax: (303) 273-8540 /##################################
                     lahr@........ /###################################
                                          /####################################
                                 http://jclahr.com/science/
 Subject: Re: Simple mini horizontal From: John or Jan Lahr JohnJan@........ Date: Tue, 04 Jan 2005 11:09:47 -0700 Hi Ted, I'm curious how your recording is going? Did you catch the M 9 Sumatra event? I'm working with some students that the Colorado School of Mines who are interested in photo detection. Would you be willing to share your electronic circuit with them? I've been recommending using one light source and two detectors arranged so that when a flag is centered, both sensors are equally illuminated. Any movement increases the light to one and decreases it to the other. Since the output of interest is the difference between the two sensors, slight variations in the brightness of the light will not cause a false signal. Cheers, John At 03:52 PM 4/7/2004, you wrote: >Hi > >John has kindly posted my attempt at a 'mini horizontal' seismograph, if you >are interested please go to: > > http://jclahr.com/science/psn/rogers/ > >I would be grateful for an comments or improvements you may think I might >incorporate in the unit, especially in the area of feed back to the light >source. > >Regards > >Ted Rogers > > > >__________________________________________________________ > >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: source of L15B geophones From: "Thomas Dick" dickthomas01@............. Date: Tue, 4 Jan 2005 12:19:43 -0600 Any one know where I could get some of these geophones? __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Off-scale Waveforms From: "Timothy Carpenter" GeoDynamics@....... Date: Tue, 4 Jan 2005 14:31:44 -0500 All, =20 Please pardon me if this winds up a double posting =96 I'm still trying = to get e-mail addresses straightened out. =20 In the normal course of my work I've occasionally run across the problem = of vibration sensors being pushed beyond their physical limits =96 i.e; the suspended mass hits the end stops. For the most part, this has never = been a significant problem for me because there's always been another way to = get the data. However, when I downloaded seismic waveforms for the Dec 26th = EQ from Wooster, Ohio and Ann Arbor, Mi I found that their data had been compromised. It appears that the seismometers hit their stops and badly affected about 2-hours of the recordings. I believe this is the case at several of the stations but certainly not all of them. I found many = intact waveforms on the PSN server. =20 I've searched through my personal references as well as exercising = Google; but to no avail. So, I turn to the vast expertise of PSN. Are any of you aware of a numerical process by which such signals can be reliably = "fixed"? I'm sure that a neural network could be trained to approximate the true signal. But I'm more interested in a dynamic model consisting of a mass-spring-dashpot model of the seismometer and a spring-dashpot model = for the stops at the end of travel. =20 Regards, -Tim- =20 Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) =20 =20

All,

 

Please pardon me if this winds up a double posting = – I'm still trying to get e-mail addresses straightened out.

 

In the normal course of my work I've occasionally run = across the problem of vibration sensors being pushed beyond their physical = limits – i.e; the suspended mass hits the end stops. For the most part, = this has never been a significant problem for me because there's always been = another way to get the data. However, when I downloaded seismic waveforms for the = Dec 26th EQ from Wooster, Ohio and Ann = Arbor, Mi I found that their data had been compromised. It appears that the seismometers = hit their stops and badly affected about 2-hours of the recordings. I = believe this is the case at several of the stations but certainly not all of them. I = found many intact waveforms on the PSN server.

 

I've searched through my personal references as well = as exercising Google; but to no avail. So, I turn to the vast expertise of = PSN. Are any of you aware of a numerical process by which such signals can be reliably "fixed"? I'm sure that a neural network could be = trained to approximate the true signal. But I'm more interested in a dynamic model consisting of a mass-spring-dashpot model of the seismometer and a spring-dashpot model for the stops at the end of = travel.

 

Regards,

-Tim-

 

Timothy Carpenter, P.E., Pres.,
GeoDynamics Consultants, Inc.
5043 Whitlow Ct.
Commerce Twp., Mi 48382
248-363-4529 (voice & fax)
248-766-1629 (cell)
geodynamics@........... = (primary)
geodynamics@....... = (secondary)

 

 

Subject: RE: source of L15B geophones From: "Doug Crice" dcrice@............ Date: Tue, 4 Jan 2005 11:55:58 -0800 L15B geophones are made by Mark Products, but the last time I looked, = they had a substantial minimum charge. Mark was acquired by Sercel and their = web site is here http://www.sercel.com/Products/frproduct2.htm under = sensors, though I don't see the L15 listed, they may be available. You might find some used ones at R. T. Clark http://www.rtclark.com/ a purveyor of used geophysical hardware. However, if you are building a seismograph, you would be a lot better = off with Larry's 3-component 4.5 Hz geophones http://psn.quake.net/geophone/index.html Doug Crice Wireless Seismic http://www.wirelessSeismic.com 12996 Somerset Drive phone 1-530-274-4445 Grass Valley, CA 95945 USA fax 1-530-274-4446 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Thomas Dick Sent: Tuesday, January 04, 2005 10:20 AM To: psn-l@.............. Subject: source of L15B geophones Any one know where I could get some of these geophones? __________________________________________________________ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: source of L15B geophones From: Angel sismos@.............. Date: Tue, 4 Jan 2005 13:26:14 +0000 Hi, The geophones in Larry's 3c boxes are L15's Angel __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Ebay: "Proof Mass Actuator Earthquake Machine" From: "Meredith Lamb" meredithlamb@............. Date: Wed, 5 Jan 2005 12:48:30 -0700 Hi all, This "could/might be" a potential seismic sensing very short period or strong motion vertical sensor conversion item. Originally, its a "shake table actuator". The seller states outright that this is NOT a seismometer. The ~5 kilogram mass has both a piezo sensor and a LDVT (linear differential variable transformer). The mass ( presumed to be either iron or a magnet?) is driven like a speaker voice coil windings around the outside of the mass. Seven inch diameter by one foot high item....but unknown total weight. The bell shaped exterior item picture, makes it look very sturdy and solid as is. On the other hand....the item could be worthless as is, or in any conversion attempt. Its (?) possible, that the metal shell alone might be worth the cost for any other derived seismometer enclosure scheme. In ways....I wonder if the piezo and LDVT were "somehow" mechanically disconnected, that the original wire coil power driven input; could then be a functional magnetic induction output velocity signal source....or....as a feedback or dampening medium? Of course, either the piezo or LDVT could be entertained also,..... but their mechanical coupling might be a motion sensing hinderance. The seller is offering a quanity of ~5 "buy it now" ($74.67), and seven other starting bid ($64.67) items. See E-Bay item #'s, 2596230058 and 3865011737, for a picture and more info. Take care, Meredith Lamb

Hi all,
 
This "could/might be" a potential seismic sensing very short period or strong motion
vertical sensor conversion item.  Originally, its a "shake table actuator".  The seller states
outright that this is NOT a seismometer.  The ~5 kilogram mass has both a piezo sensor and
a LDVT (linear differential variable transformer).  The mass ( presumed to be either iron or
a magnet?) is driven like a speaker voice coil windings around the outside of the mass. 
Seven inch diameter by one foot high item....but unknown total weight.  The bell shaped
exterior item picture, makes it look very sturdy and solid as is.  On the other hand....the item
could be worthless as is, or in any conversion attempt.   Its (?) possible, that the metal shell
alone might be worth the cost for any other derived seismometer enclosure scheme.
 
In ways....I wonder if the piezo and LDVT were "somehow" mechanically disconnected, that
the original wire coil power driven input; could then be a functional magnetic induction output
velocity signal source....or....as a feedback or dampening medium?  Of course, either the
piezo or LDVT could be entertained also,..... but their mechanical coupling might be a
motion sensing hinderance. 
 
The seller is offering a quanity of ~5 "buy it now" ($74.67), and seven other starting bid
($64.67) items.  See E-Bay item #'s, 2596230058 and 3865011737, for a picture and more info. 
 
Take care, Meredith Lamb
 
 

Subject: SDR Board For Sale From: "Rex Klopfenstein, Jr." rklopfen@......... Date: Wed, 5 Jan 2005 21:26:35 -0500 All I have just ordered a new serial SDR card so I am selling my DOS SDR card on EBay. Do a search with seismic and you should find. Thanks Rex Klopfenstein Bowling Green, OH

All

I have just ordered a new serial SDR card so I am = selling my DOS SDR card on EBay.  Do a = search with seismic and you should find.

Thanks


Rex Klopfenstein

Bowling Green, OH

Subject: Surface waves from Sumatra M 9.0 From: John or Jan Lahr JohnJan@........ Date: Thu, 06 Jan 2005 07:41:27 -0700 If you haven't taken a look at the IRIS "Image of the Week" yet, check out this page: file:///C:/education/Sumatra%209.0/surface_waves.htm The image shows seismic records from stations distributed around the globe and surface waves that traveled twice around! Questions to think about -- Why does the y-axis stop at 180 degrees? Why would the amplitude of the surface waves fall off around 90 degrees and then increase at 180 degrees again? Cheers, John __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Surface waves from Sumatra M 9.0 From: "Larry P Thomas" lpthomas@......... Date: Thu, 6 Jan 2005 10:18:11 -0600 John, Your link points to a file which is local on your hard drive and I can't, of course, pull that up with my browser. Does it exist on the web someplace? file:///C:/education/Sumatra%209.0/surface_waves.htm Thanks, Larry P. Thomas, wa0gwa Imagine it/Achieve it --- Dream it/Become it Larry P. Thomas, wa0gwa 1 913 244-8761 Krell Technologies (http://www.krell.com) 8960 Bond, Overland Park, KS 66214-1722 USA __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Surface waves from Sumatra M 9.0 From: Bob Hancock Bob_Hancock@............ Date: Thu, 06 Jan 2005 09:27:36 -0700 This link works..... http://dmc.iris.washington.edu/about/ENO/iow.htm -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Larry P Thomas Sent: Thursday, January 06, 2005 09:18 To: psn-l@.............. Subject: RE: Surface waves from Sumatra M 9.0 John, Your link points to a file which is local on your hard drive and I can't, of course, pull that up with my browser. Does it exist on the web someplace? file:///C:/education/Sumatra%209.0/surface_waves.htm Thanks, Larry P. Thomas, wa0gwa Imagine it/Achieve it --- Dream it/Become it Larry P. Thomas, wa0gwa 1 913 244-8761 Krell Technologies (http://www.krell.com) 8960 Bond, Overland Park, KS 66214-1722 USA __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Surface waves from Sumatra M 9.0 From: "Thomas Dick" dickthomas01@............. Date: Thu, 6 Jan 2005 11:02:46 -0600 type in iris image of the week -- your browser should show it as the first or second option > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Surface waves from Sumatra M 9.0, 2nd Version From: John or Jan Lahr JohnJan@........ Date: Thu, 06 Jan 2005 12:10:20 -0700 If you haven't taken a look at the IRIS "Image of the Week" yet, check out this page (with the now correct URL!): http://www.iris.edu/about/ENO/iow.htm The image shows seismic records from stations distributed around the globe and surface waves that traveled twice around! Questions to think about -- Why does the y-axis stop at 180 degrees? Why would the amplitude of the surface waves fall off around 90 degrees and then increase at 180 degrees again? Cheers, John __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Surface waves from Sumatra M 9.0, 2nd Version From: "twleiper@......... twleiper@juno.com Date: Thu, 6 Jan 2005 19:37:47 GMT I would suspect destructive interference of the wave fronts at the quarter-wave point (50 minutes) assuming the resonance of the "global tank circuit" is 200 minutes. Either that or some type of phase shift. How about the coriolis effect ? :-) -- John or Jan Lahr wrote: If you haven't taken a look at the IRIS "Image of the Week" yet, check out this page (with the now correct URL!): http://www.iris.edu/about/ENO/iow.htm The image shows seismic records from stations distributed around the globe and surface waves that traveled twice around! Questions to think about -- Why does the y-axis stop at 180 degrees? Why would the amplitude of the surface waves fall off around 90 degrees and then increase at 180 degrees again? Cheers, John __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Surface waves from Sumatra M 9.0, 2nd Version From: John Hernlund hernlund@............ Date: Thu, 6 Jan 2005 13:48:16 -0800 John, Thanks for pointing this out. Hint for answer: Earth is spherical, not circular... Cheers! John On Thursday, January 6, 2005, at 11:10 AM, John or Jan Lahr wrote: > If you haven't taken a look at the IRIS "Image of the Week" yet, > check out this page (with the now correct URL!): > http://www.iris.edu/about/ENO/iow.htm > > The image shows seismic records from stations distributed around > the globe and surface waves that traveled twice around! > > Questions to think about -- Why does the y-axis stop at 180 degrees? > Why would the amplitude of the surface waves fall off around 90 degrees > and then increase at 180 degrees again? > > Cheers, > John > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Surface waves from Sumatra M 9.0, 2nd Version From: Jack Ivey ivey@.......... Date: Thu, 6 Jan 2005 17:02:06 -0500 Ok, I'll bite. The wave front is always a circle, but the size of the circle varies. Near the source, it is a small circle and the energy is concentrated. At 90 degrees, it is a large (great) circle, the same diameter as the earth, spreading the energy out. At the antipodes, the circle shrinks again, concentrating the energy. This causes the blip in amplitude at angles near 180. The wave is also dissipating energy and dispersing, so the blip is superimposed on an overall decreasing amplitude. The same thing happens with VLF radio transmissions traveling around the globe. Jack On Thursday, January 6, 2005, at 11:10 AM, John or Jan Lahr wrote: > If you haven't taken a look at the IRIS "Image of the Week" yet, > check out this page (with the now correct URL!): > http://www.iris.edu/about/ENO/iow.htm > > The image shows seismic records from stations distributed around > the globe and surface waves that traveled twice around! > > Questions to think about -- Why does the y-axis stop at 180 degrees? > Why would the amplitude of the surface waves fall off around 90 degrees > and then increase at 180 degrees again? > > Cheers, > John > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Surface waves from Sumatra M 9.0, 2nd Version From: Mark Robinson mark.robinson@............... Date: Fri, 07 Jan 2005 11:15:10 +1300 John Hernlund wrote: > John, > > Thanks for pointing this out. > > Hint for answer: Earth is spherical, not circular... > > Cheers! > John > > On Thursday, January 6, 2005, at 11:10 AM, John or Jan Lahr wrote: > >> If you haven't taken a look at the IRIS "Image of the Week" yet, >> check out this page (with the now correct URL!): >> http://www.iris.edu/about/ENO/iow.htm >> >> The image shows seismic records from stations distributed around >> the globe and surface waves that traveled twice around! >> >> Questions to think about -- Why does the y-axis stop at 180 degrees? >> Why would the amplitude of the surface waves fall off around 90 degrees >> and then increase at 180 degrees again? >> >> Cheers, >> John Hi folks, If you have access to a room with a dome, go there with a friend, take up positions on opposite sides, and whisper. Mark Robinson ------------- 07 Jan 1924 George Gershwin composes Rhapsody in Blue. 07 Jan 1952 Ike offers to accept GOP Presidential Nomination. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Surface waves from Sumatra M 9.0, 2nd Version From: "Timothy Carpenter" GeoDynamics@....... Date: Thu, 6 Jan 2005 17:31:04 -0500 John, You asked a couple of questions after giving us the link to the Global Displacement Wavefield. I started to write up a quick answer, but since = I'm new to the group I thought I better find out a bit more about who was = asking the questions. I'm glad I did. I'll leave the questions unanswered for others to ponder. I presume after some reasonable amount of time, you = will provide the answers.=20 -Tim- Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of twleiper@........ Sent: Thursday, January 06, 2005 2:38 PM To: psn-l@.............. Subject: Re: Surface waves from Sumatra M 9.0, 2nd Version I would suspect destructive interference of the wave fronts at the quarter-wave point (50 minutes) assuming the resonance of the "global tank circuit" is 200 minutes. Either that or some type of phase shift. How about the coriolis effect ? :-) -- John or Jan Lahr wrote: If you haven't taken a look at the IRIS "Image of the Week" yet, check out this page (with the now correct URL!): http://www.iris.edu/about/ENO/iow.htm The image shows seismic records from stations distributed around the globe and surface waves that traveled twice around! Questions to think about -- Why does the y-axis stop at 180 degrees? Why would the amplitude of the surface waves fall off around 90 degrees and then increase at 180 degrees again? Cheers, John=20 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Global Simulation of Sumarta EQ From: "Timothy Carpenter" GeoDynamics@....... Date: Sat, 8 Jan 2005 05:07:41 -0500 This program provides an excellent representation of how seismic waves travel through and around the globe. http://www.geol.binghamton.edu/faculty/jones/jones.html Scroll down to: "Seismic Waves: A program for the visualization of wave propagation" Download seiswave.readme and SeismicWavesSetup.exe. Read the readme file and then Run the setup program. When the installation is finished, run the animation and select the Sumatra Quake. After it has finished with one quake, the program moves on to another. Regards, -Tim- Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary)

This program = provides an excellent representation of how seismic waves travel through and around = the globe.

http://www.geol.binghamton.edu/facul= ty/jones/jones.html

Scroll down to: = "Seismic Waves: A program for the visualization of wave propagation"

Download seiswave.readme and SeismicWavesSetup.exe.

Read the readme file and then Run = the setup program= .

When the installation is finished, = run the animation and select the Sumatra Quake. After it has finished with one = quake, the program= moves on to another.

Regards,

-Tim-

Timothy Carpenter, P.E., Pres.,
GeoDynamics Consultants, Inc.
5043 Whitlow Ct.
Commerce Twp., Mi 48382
248-363-4529 (voice & fax)
248-766-1629 (cell)
geodynamics@........... = (primary)
geodynamics@....... = (secondary)

 

 

Subject: Iris Waveform Chart From: "Connie and Jim Lehman" lehmancj@........... Date: Sun, 9 Jan 2005 19:02:32 -0500 PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra 12/26/04 = event. The surface wave arrivals of multiple stations exhibited by = distance, and text, makes a super graphic. I was wondering about the = occurrence of a seismic caustic at the appropriate degree distance. Was = the gap at 160 degree area due to no reporting station near the = "caustic" distance. In periodic recording here we've copied three = caustics in 20 years--I believe the events were southwest of Australia = for us--not a very hot spot. The 18 sec long period system at James Madison Un. (Virginia) = working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) = nicely, but the 9.0 event read 20 min after P-diff arrived and then went = off scale for 100 minutes and returned to normal recording for the 7.1 = event at 04:21. One can conclude, surface wave arrivals for us (at = approx. 145 degrees) were obscured. Keep up the good work. Jim Lehman
PSN--thanks for the Iris Waveform Chart = for the=20 9.0 Sumatra  12/26/04 event.  The surface wave arrivals of = multiple=20 stations exhibited by distance, and text,  makes a super = graphic.  I=20 was wondering about  the occurrence of a seismic caustic at the = appropriate=20 degree distance.  Was the gap at 160 degree area due to no = reporting=20 station near the "caustic" distance.  In periodic recording here = we've=20 copied three caustics  in 20 years--I believe the events were = southwest of=20 Australia for us--not a very hot spot.
    The 18 sec long = period system=20 at James Madison Un.  (Virginia) working into a graphic readout = read the=20 8.1 Macquarie Is. event-(l2/23) nicely, but the 9.0 event read 20 min = after=20 P-diff arrived and then went off scale for 100 minutes and returned to = normal=20 recording for the 7.1 event at 04:21.  One can conclude, = surface wave=20 arrivals for us (at approx. 145 degrees) were obscured.  = Keep up=20 the good work.
          =  =20 Jim Lehman
Subject: ebay auction From: BOB BARNS royb1@........... Date: Sat, 15 Jan 2005 13:18:17 -0500 Hi gang, Vintage Seismoscope U-17 Earthquake Measurement Tool Item number: 6146607454 ends Jan. 20 Bob Barns __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: ebay auction From: BOB BARNS royb1@........... Date: Sat, 15 Jan 2005 13:20:08 -0500 Hi gang, I should have put both of these in one message, sorry. Nomis NCSC 5000 Seismograph Vibratech Item number: 6146573473 ends Jan 20 Bob Barns __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: ebay auction From: BOB BARNS royb1@........... Date: Mon, 24 Jan 2005 10:24:25 -0500 Another geophone-- WORKING SEISMOGRAPH SEISMIC GEOPHONE Item number: 6148741624 ends Jan. 29 Bob Barns __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: ebay auctions From: BOB BARNS royb1@........... Date: Mon, 31 Jan 2005 21:08:27 -0500 Wilmot SR-100 Seismoscope Earthquake Recorder Survey Type Strong-Motion Stainless-Steel Unit = Works! Item number: 6150616013 ends Feb 9 v. interesting! but not for New Jersey. ------------- WORKING SEISMOGRAPH SEISMIC GEOPHONE Item number: 6150843011 ends Feb 6 another geophone Bob Barns __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Helioseismology From: Bob Hancock Bob.Hancock@............ Date: Tue, 01 Feb 2005 09:09:02 -0700 Space Weather had an interesting article on helioseismology, or how they are using sound waves to map the interior of the sun. http://spaceweather.com Article on Heliseismic Holography http://spaceweather.com/glossary/farside.html Article on Helioseismology http://science.msfc.nasa.gov/ssl/pad/solar/p_modes.htm

Space Weather had an interesting article on helioseismology, or how they are using sound waves to map the interior of the sun.

 

http://spaceweather.com

 

Article on Heliseismic Holography

 

            http://spaceweather.com/glossary/farside.html

 

Article on Helioseismology

 

            http://science.msfc.nasa.gov/ssl/pad/solar/p_modes.htm

 

Subject: RE: Iris Waveform Chart From: "Timothy Carpenter" GeoDynamics@....... Date: Sat, 5 Feb 2005 16:33:00 -0500 I should probably know =96 but I don't. What is the "caustic" distance? = And for that matter, what is the "caustic"? Regards, -Tim- =20 Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) =20 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Connie and Jim Lehman Sent: Sunday, January 09, 2005 7:03 PM To: psn-l@.............. Subject: Iris Waveform Chart =20 PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra 12/26/04 = event. The surface wave arrivals of multiple stations exhibited by distance, = and text, makes a super graphic. I was wondering about the occurrence of = a seismic caustic at the appropriate degree distance. Was the gap at 160 degree area due to no reporting station near the "caustic" distance. In periodic recording here we've copied three caustics in 20 years--I = believe the events were southwest of Australia for us--not a very hot spot. The 18 sec long period system at James Madison Un. (Virginia) = working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) nicely, = but the 9.0 event read 20 min after P-diff arrived and then went off scale = for 100 minutes and returned to normal recording for the 7.1 event at 04:21. One can conclude, surface wave arrivals for us (at approx. 145 degrees) = were obscured. Keep up the good work. Jim Lehman

I should probably know – but = I don't. What is the "caustic" distance? And for that matter, = what is the "caustic"?

Regards,

-Tim-

 

Timothy = Carpenter, P.E., Pres.,
GeoDynamics Consultants, Inc.
5043 Whitlow Ct.
Commerce Twp., Mi 48382
248-363-4529 (voice & fax)
248-766-1629 (cell)
geodynamics@........... = (primary)
geodynamics@....... = (secondary)

 

 

-----Original = Message-----
From: = psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Connie and Jim Lehman
Sent: Sunday, January 09, = 2005 7:03 PM
To: = psn-l@..............
Subject: Iris Waveform = Chart

 

PSN--thanks for the Iris = Waveform Chart for the 9.0 Sumatra  12/26/04 event.  The surface wave = arrivals of multiple stations exhibited by distance, and text,  makes a = super graphic.  I was wondering about  the occurrence of a seismic = caustic at the appropriate degree distance.  Was the gap at 160 degree area = due to no reporting station near the "caustic" distance.  In = periodic recording here we've copied three caustics  in 20 years--I believe = the events were southwest of Australia for us--not a very hot = spot.

    The 18 = sec long period system at James Madison Un.  (Virginia) working into a = graphic readout read the 8.1 Macquarie Is. event-(l2/23) nicely, but the 9.0 = event read 20 min after P-diff arrived and then went off scale for 100 minutes and returned to normal recording for the 7.1 event at 04:21.  = One can conclude, surface wave arrivals for us (at approx. 145 = degrees) were obscured.  Keep up the good work.

    &nbs= p;       Jim Lehman

Subject: RE: Iris Waveform Chart From: "Jorma Kanninen" jorma@............. Date: Sat, 5 Feb 2005 23:34:31 +0000 Hi Tim, Now I'm getting a bit puzzled ! Cheers, Jorma From: psn-l-request@.............. [mailto:psn-l-request@webtroni= cs.com] On Behalf Of Timothy Carpenter Sent: 05 February 2005 21:33 To: psn-l@.............. Subject: RE: Iris Waveform Chart I should probably know =96 but I don't. What is the "caustic" dis= tance? And for that matter, what is the "caustic"? Regards, -Tim- Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@webtroni= cs.com] On Behalf Of Connie and Jim Lehman Sent: Sunday, January 09, 2005 7:03 PM To: psn-l@.............. Subject: Iris Waveform Chart PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra 12/2= 6/04 event. The surface wave arrivals of multiple stations exhib= ited by distance, and text, makes a super graphic. I was wonder= ing about the occurrence of a seismic caustic at the appropriate= degree distance. Was the gap at 160 degree area due to no repor= ting station near the "caustic" distance. In periodic recording=20= here we've copied three caustics in 20 years--I believe the even= ts were southwest of Australia for us--not a very hot spot. The 18 sec long period system at James Madison Un. (Virginia= ) working into a graphic readout read the 8.1 Macquarie Is. event= -(l2/23) nicely, but the 9.0 event read 20 min after P-diff arriv= ed and then went off scale for 100 minutes and returned to normal= recording for the 7.1 event at 04:21. One can conclude, surface= wave arrivals for us (at approx. 145 degrees) were obscured. Ke= ep up the good work. Jim Lehman
Hi Tim,
 
Now I'm getting a bit puzzled !
 
Cheers,
 
Jorma

From: psn-l-request@webtronic= s.com [mailto:psn-l-request@............... On Behalf Of Timothy= Carpenter
Sent: 05 February 2005 21:33
To: psn-l@..............
Subject: RE: Iris Waveform Chart

I shou= ld probably know – but I don't. What is the "caustic" distance? And for that= matter, what is the "caustic"?

Regard= s,

-Tim-

 

Timothy Carpenter, P.E., Pres.,
GeoDyn= amics Consultants, Inc.
5043 Whitlow Ct.
Commerce Twp., Mi 48382
248-363-45= 29 (voice & fax)
248-766-1629 (cell)
geodynamics@........... (primary)
geodynamics@a= tt.net (secondary)

 

 

-----Original Message-----
From:= psn-l-request@.............. [mailto:psn-l-request@............... ] On Behalf Of Connie and Ji= m Lehman
Sent: S= unday, January 09, 2005 7:03 PM
To: psn-l@..............
Subj= ect: Iris Waveform Chart

 

=

PSN-= -thanks for the Iris Waveform Chart for the 9.0 Sumatra  12/26/04 event.&nbs= p; The surface wave arrivals of multiple stations exhibited by distance, and tex= t,  makes a super graphic.  I was wondering about  the occurrence= of a seismic caustic at the appropriate degree distance.  Was the gap at=20= 160 degree area due to no reporting station near the "caustic" distance.  In= periodic recording here we've copied three caustics  in 20 years--I b= elieve the events were southwest of Australia for us--not a very hot spot.

&nbs= p;   The 18 sec long period system at James Madison Un.  (Virginia) w= orking into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) nicely,=20= but the 9.0 event read 20 min after P-diff arrived and then went off scale fo= r 100 minutes and returned to normal recording for the 7.1 event at 04:21. = ; One can conclude, surface wave arrivals for us (at approx. 145 degre= es) were obscured.  Keep up the good work.=

   &= nbsp;        Jim Lehman

Subject: RE: Iris Waveform Chart From: "Jorma Kanninen" jorma@............. Date: Sat, 5 Feb 2005 23:42:20 +0000 FYI The line caustic behavior has been discussed since Chang and Refs= dal (1979) mentioned inverse-square-root-of-the-distance dependen= ce of the amplification of the images near the critical curve in=20= a study of a single point mass under the influence of a constant=20= shear due to a larger mass. A quarter century later, Gaudi and Pe= tters (2001) interprets that the distance is {\it a vertical dist= ance to the caustic}. It is an erroneous misinterpretation. We rehash Rhie and Bennett (1999) where the caustic behavior of t= he binary lenses was derived to study the feasibility of limb dar= kening measurements in caustic crossing microlensing events. ~({\= it 1}) $J =3D \pm \sqrt{4\delta\omega_{2-} J_-}$ where ~$\delta\o= mega\parallel\bar\partial J$, and $\delta\omega_{2-}$ and $J_-$ a= re $E_-$-components of $\delta\omega$ (the source position shift=20= from the caustic curve) and $2\bar\partial J$ (the gradient of th= e Jacobian determinant) respectively; ~({\it 2}) The critical eig= envector $\pm E_-$ is normal to the caustic curve and easily dete= rmined from the analytic function $\kappa$-field; ~({\it 3}) Near= a cusp ($J_- =3D 0$) is of a behavior of the third order, and th= e direction of $\bar\partial J$ with respect to the caustic curve= changes rapidly because a cusp is an accumulation point; ~({\it=20= 4}) On a planetary caustic, $|\partial J|\sim \sqrt{1/\epsilon_{p= l}}$ is large and power expansion does not necessarily converge o= ver the size of the lensed star. In practice, direct numerical su= mmation is inevitable. We also note that a lens equation with constant shear is intrinsi= cally incomplete and requires supplementary physical assumptions=20= and interpretations in order to be a viable model for a lensing s= ystem. Cheers, Jorma ________________________________ From: psn-l-request@.............. [mailto:psn-l-request@webtroni= cs.com] On Behalf Of Timothy Carpenter Sent: 05 February 2005 21:33 To: psn-l@.............. Subject: RE: Iris Waveform Chart I should probably know =E2=80=93 but I don't. What is the "causti= c" distance? And for that matter, what is the "caustic"? Regards, -Tim- Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@webtroni= cs.com] On Behalf Of Connie and Jim Lehman Sent: Sunday, January 09, 2005 7:03 PM To: psn-l@.............. Subject: Iris Waveform Chart PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra 12/2= 6/04 event. The surface wave arrivals of multiple stations exhib= ited by distance, and text, makes a super graphic. I was wonder= ing about the occurrence of a seismic caustic at the appropriate= degree distance. Was the gap at 160 degree area due to no repor= ting station near the "caustic" distance. In periodic recording=20= here we've copied three caustics in 20 years--I believe the even= ts were southwest of Australia for us--not a very hot spot. The 18 sec long period system at James Madison Un. (Virginia= ) working into a graphic readout read the 8.1 Macquarie Is. event= -(l2/23) nicely, but the 9.0 event read 20 min after P-diff arriv= ed and then went off scale for 100 minutes and returned to normal= recording for the 7.1 event at 04:21. One can conclude, surface= wave arrivals for us (at approx. 145 degrees) were obscured. Ke= ep up the good work. Jim Lehman __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Iris Waveform Chart From: John or Jan Lahr johnjan@........ Date: Sat, 05 Feb 2005 18:06:53 -0800 Caustic. An earthquake sends waves out in all directions. In ray theory, one=20 considers just one "ray" at a time. A ray that starts out going horizontally will soon reach= =20 the surface of the earth, where as a ray that starts out going directly downward will go=20 straight through the Earth and reach the "other side of the Earth" at a distance of 180=20 degrees ( the angular distance as measured from the center of the Earth). If we consider an ray= =20 leaving the earthquake source in the horizontal direction to have a "take-off" angle of= =20 zero, while a ray going straight down has a take-off angle of 90, then, in general, the=20 greater the take off angle of the ray, the greater the distance the ray emerges. However, due to the changes in velocity of the Earth with depth, most= notably the decrease in P-wave velocity in the outer core as compared to the lower= =20 mantle, there are some distances where, as the take off angle increases the distance=20 where the ray emerges starts to DECREASE! At these points, called caustics, there=20 is a focusing effect leading to higher amplitude waves being observed. I'm sure others will add to this! Cheers, John At 03:34 PM 2/5/2005, you wrote: >Hi Tim, > >Now I'm getting a bit puzzled ! > >Cheers, > >Jorma > > >---------- >From: psn-l-request@.............. [mailto:psn-l-request@.................. >On Behalf Of Timothy Carpenter >Sent: 05 February 2005 21:33 >To: psn-l@.............. >Subject: RE: Iris Waveform Chart > >I should probably know =96 but I don't. What is the "caustic" distance? And= =20 >for that matter, what is the "caustic"? > >Regards, > >-Tim- > > > >Timothy Carpenter, P.E., Pres., >GeoDynamics Consultants, Inc. >5043 Whitlow Ct. >Commerce Twp., Mi 48382 >248-363-4529 (voice & fax) >248-766-1629 (cell) >geodynamics@........... (primary) >geodynamics@....... (secondary) > > > > > >-----Original Message----- >From: psn-l-request@.............. [mailto:psn-l-request@.................. >On Behalf Of Connie and Jim Lehman >Sent: Sunday, January 09, 2005 7:03 PM >To: psn-l@.............. >Subject: Iris Waveform Chart > > > >PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra 12/26/04=20 >event. The surface wave arrivals of multiple stations exhibited by=20 >distance, and text, makes a super graphic. I was wondering about the=20 >occurrence of a seismic caustic at the appropriate degree distance. Was=20 >the gap at 160 degree area due to no reporting station near the "caustic"= =20 >distance. In periodic recording here we've copied three caustics in 20=20 >years--I believe the events were southwest of Australia for us--not a very= =20 >hot spot. > > The 18 sec long period system at James Madison Un. (Virginia)=20 > working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23)=20 > nicely, but the 9.0 event read 20 min after P-diff arrived and then went= =20 > off scale for 100 minutes and returned to normal recording for the 7.1=20 > event at 04:21. One can conclude, surface wave arrivals for us (at=20 > approx. 145 degrees) were obscured. Keep up the good work. > > Jim Lehman __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Iris Waveform Chart From: "Connie and Jim Lehman" lehmancj@........... Date: Sun, 6 Feb 2005 18:17:50 -0500 Tim & others- According to Bath, Intro. to Seismology, the author explains a seismic = caustic as follows. In a model of Earth with Core 1/2 dia. of the Earth = Sphere, and a ratio of density l:1.2, every point situated more than 155 = degrees from the surface event will receive not one but two PKP waves = which propigate along different paths. Exactly at 155 degrees, these = waves coincide and result in a great concentration of energy--or a = Caustic. =20 For reasons not easily explained, this caustic --in real earth = seismicity occurs at or near 144 degrees. The net effect of the Caustic = is a ring of PKP concentration 36 degrees away from the "antipode" of = the event. ( Remember direct P-waves observe quiet time from 103 to 144 = degrees ) Although I have never seen this demo, I understand a sphere of high = density glass enclosed with a sphere of lower density glass will show a = similar ring of lazer light entering the far side. Of course acoustic = caustics can be demonstrated. The few caustics noted here (long Period) have a signature very = unique from the usual events of S. Pacific. The front loading of P = related waves are larger than any of the other wave fronts, expecially = in deep events where surface waves are minimized. No doubt there are better explanations (Thanks Jorma) of this = seismic phenomenon. Do the geometry of P energy through the Core, and = one gets an idea of what is going on. Jim Lehman ----- Original Message -----=20 From: Timothy Carpenter=20 To: psn-l@................. Sent: Saturday, February 05, 2005 4:33 PM Subject: RE: Iris Waveform Chart I should probably know - but I don't. What is the "caustic" distance? = And for that matter, what is the "caustic"? Regards, -Tim- Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) -----Original Message----- From: psn-l-request@.............. = [mailto:psn-l-request@............... On Behalf Of Connie and Jim Lehman Sent: Sunday, January 09, 2005 7:03 PM To: psn-l@.............. Subject: Iris Waveform Chart PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra 12/26/04 = event. The surface wave arrivals of multiple stations exhibited by = distance, and text, makes a super graphic. I was wondering about the = occurrence of a seismic caustic at the appropriate degree distance. Was = the gap at 160 degree area due to no reporting station near the = "caustic" distance. In periodic recording here we've copied three = caustics in 20 years--I believe the events were southwest of Australia = for us--not a very hot spot. The 18 sec long period system at James Madison Un. (Virginia) = working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) = nicely, but the 9.0 event read 20 min after P-diff arrived and then went = off scale for 100 minutes and returned to normal recording for the 7.1 = event at 04:21. One can conclude, surface wave arrivals for us (at = approx. 145 degrees) were obscured. Keep up the good work. Jim Lehman
Tim & others-
 
According to Bath, Intro. to=20 Seismology, the author explains a seismic caustic as = follows.  In=20 a model of Earth with Core 1/2 dia. of the Earth Sphere, and a ratio of = density=20 l:1.2, every point situated more than 155 degrees from the surface event = will=20 receive not one but two PKP waves which propigate along different=20 paths.  Exactly at 155 degrees, these waves coincide and result in = a great=20 concentration of energy--or a Caustic. 
   For reasons not easily = explained,=20 this caustic --in real earth seismicity occurs at or near=20 144 degrees.  The net effect of the Caustic is a ring of PKP=20 concentration 36 degrees away from the "antipode" of the event.  ( = Remember=20 direct P-waves observe quiet time from 103 to 144 degrees=20 )
    Although I have never = seen this=20 demo, I understand a sphere of high density glass enclosed with a sphere = of=20 lower density glass will show a similar ring of lazer light entering the = far=20 side.  Of course acoustic caustics can be=20 demonstrated.
   The few caustics noted here = (long=20 Period) have a signature very unique from the usual events of S. = Pacific. =20 The front loading of P related waves are larger than any of the other = wave=20 fronts, expecially in deep events where surface waves are=20 minimized.
   No doubt there are better=20 explanations     (Thanks Jorma)  of  this = seismic=20 phenomenon.   Do the geometry of P energy through the Core, and one = gets an=20 idea of what is going on.
          =        =20 Jim Lehman
----- Original Message -----
From:=20 Timothy=20 Carpenter
Sent: Saturday, February 05, = 2005 4:33=20 PM
Subject: RE: Iris Waveform = Chart

I should = probably=20 know – but I don't. What is the "caustic" distance? And for that = matter, what=20 is the "caustic"?

Regards,

-Tim-

 

Timothy = Carpenter, P.E., Pres.,
GeoDynamics = Consultants, Inc.
5043 Whitlow Ct.
Commerce Twp., Mi=20 48382
248-363-4529 (voice & fax)
248-766-1629 (cell)
geodynamics@...........=20 (primary)
geodynamics@.......=20 (secondary)

 

 

-----Original=20 Message-----
From:=20 psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Connie and Jim=20 Lehman
Sent: = Sunday, January=20 09, 2005 7:03 PM
To:=20 psn-l@..............
Subject:=20 Iris Waveform Chart

 

PSN--thanks for the=20 Iris Waveform Chart for the 9.0 Sumatra  12/26/04 event.  = The=20 surface wave arrivals of multiple stations exhibited by distance, and=20 text,  makes a super graphic.  I was wondering about  = the=20 occurrence of a seismic caustic at the appropriate degree = distance.  Was=20 the gap at 160 degree area due to no reporting station near the = "caustic"=20 distance.  In periodic recording here we've copied three = caustics =20 in 20 years--I believe the events were southwest of Australia for = us--not a=20 very hot spot.

   =20 The 18 sec long period system at James Madison Un.  (Virginia) = working=20 into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) = nicely, but=20 the 9.0 event read 20 min after P-diff arrived and then went off scale = for 100=20 minutes and returned to normal recording for the 7.1 event at = 04:21. =20 One can conclude, surface wave arrivals for us (at approx. = 145=20 degrees) were obscured.  Keep up the good=20 work.

           = =20 Jim = Lehman

Subject: RE: Iris Waveform Chart From: "Timothy Carpenter" GeoDynamics@....... Date: Sun, 6 Feb 2005 19:15:23 -0500 Fascinating. Thanks for the explanation. I went back and re-ran Alan = Jones's animation of wave propagation through the earth, set the cursor at about = 145 degrees and watched. That program is an excellent teaching aid. =20 So, is the term Caustic used only for the special case of the = constructive interference at 155-degrees (or 144) or is it used for any case of constructive interference? =20 -Tim- =20 Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) =20 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Connie and Jim Lehman Sent: Sunday, February 06, 2005 6:18 PM To: psn-l@.............. Subject: Re: Iris Waveform Chart =20 Tim & others- =20 According to Bath, Intro. to Seismology, the author explains a seismic caustic as follows. In a model of Earth with Core 1/2 dia. of the Earth Sphere, and a ratio of density l:1.2, every point situated more than 155 degrees from the surface event will receive not one but two PKP waves = which propigate along different paths. Exactly at 155 degrees, these waves coincide and result in a great concentration of energy--or a Caustic. =20 For reasons not easily explained, this caustic --in real earth = seismicity occurs at or near 144 degrees. The net effect of the Caustic is a ring = of PKP concentration 36 degrees away from the "antipode" of the event. ( Remember direct P-waves observe quiet time from 103 to 144 degrees ) Although I have never seen this demo, I understand a sphere of high density glass enclosed with a sphere of lower density glass will show a similar ring of lazer light entering the far side. Of course acoustic caustics can be demonstrated. The few caustics noted here (long Period) have a signature very = unique from the usual events of S. Pacific. The front loading of P related = waves are larger than any of the other wave fronts, expecially in deep events where surface waves are minimized. No doubt there are better explanations (Thanks Jorma) of this seismic phenomenon. Do the geometry of P energy through the Core, and = one gets an idea of what is going on. Jim Lehman ----- Original Message -----=20 From: Timothy Carpenter =20 To: psn-l@................. Sent: Saturday, February 05, 2005 4:33 PM Subject: RE: Iris Waveform Chart =20 I should probably know =96 but I don't. What is the "caustic" distance? = And for that matter, what is the "caustic"? Regards, -Tim- =20 Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) =20 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Connie and Jim Lehman Sent: Sunday, January 09, 2005 7:03 PM To: psn-l@.............. Subject: Iris Waveform Chart =20 PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra 12/26/04 = event. The surface wave arrivals of multiple stations exhibited by distance, = and text, makes a super graphic. I was wondering about the occurrence of = a seismic caustic at the appropriate degree distance. Was the gap at 160 degree area due to no reporting station near the "caustic" distance. In periodic recording here we've copied three caustics in 20 years--I = believe the events were southwest of Australia for us--not a very hot spot. The 18 sec long period system at James Madison Un. (Virginia) = working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) nicely, = but the 9.0 event read 20 min after P-diff arrived and then went off scale = for 100 minutes and returned to normal recording for the 7.1 event at 04:21. One can conclude, surface wave arrivals for us (at approx. 145 degrees) = were obscured. Keep up the good work. Jim Lehman

Fascinating. Thanks for the = explanation. I went back and re-ran Alan Jones's animation of wave propagation through = the earth, set the cursor at about 145 degrees and watched. That = program is an excellent = teaching aid.

 

So, is the term Caustic used only = for the special case of the constructive interference at 155-degrees (or 144) or = is it used for any case of constructive interference?

 

-Tim-

 

Timothy = Carpenter, P.E., Pres.,
GeoDynamics Consultants, Inc.
5043 Whitlow = Ct.
Commerce Twp., Mi 48382
248-363-4529 (voice & fax)
248-766-1629 (cell)
geodynamics@........... = (primary)
geodynamics@....... = (secondary)

 

 

-----Original = Message-----
From: = psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Connie and Jim Lehman
Sent: Sunday, February 06, 2005 6:18 PM
To: = psn-l@..............
Subject: Re: Iris = Waveform Chart

 

Tim & = others-

 

According to = Bath, Intro. to = Seismology, the author explains a seismic caustic as follows.  In a model of Earth = with Core 1/2 dia. of the Earth Sphere, and a ratio of density l:1.2, every = point situated more than 155 degrees from the surface event will receive not = one but two PKP waves which propigate along different paths.  Exactly = at 155 degrees, these waves coincide and result in a great concentration of = energy--or a Caustic. 

   For reasons = not easily explained, this caustic --in real earth seismicity occurs at or near 144 degrees.  The net effect of the Caustic is a ring of PKP concentration 36 degrees away from the "antipode" of the = event.  ( Remember direct P-waves observe quiet time from 103 to 144 degrees = )

    Although = I have never seen this demo, I understand a sphere of high density glass = enclosed with a sphere of lower density glass will show a similar ring of lazer light entering the far side.  Of course acoustic caustics can be = demonstrated.

   The few = caustics noted here (long Period) have a signature very unique from the usual events of = S. Pacific.  The front loading of P related waves are larger than any = of the other wave fronts, expecially in deep events where surface waves are = minimized.

   No doubt there = are better explanations     (Thanks Jorma)  = of  this seismic phenomenon.   Do the geometry of P energy through the Core, = and one gets an idea of what is going on.

    &nbs= p;            = ; Jim Lehman

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

To:<= /font> psn-l@..............

Sent: Saturday, February 05, 2005 4:33 PM

Subject: RE: Iris Waveform Chart

 

I should = probably know – but I don't. What is the "caustic" distance? And for = that matter, what is the "caustic"?

Regards,

-Tim-

 

Timothy Carpenter, P.E., Pres.,
GeoDynamics Consultants, Inc.
5043 Whitlow = Ct.
Commerce Twp., Mi 48382
248-363-4529 (voice & fax)
248-766-1629 (cell)
geodynamics@........... = (primary)
geodynamics@....... = (secondary)

 

 

-----Original = Message-----
From: = psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Connie and Jim Lehman
Sent: Sunday, January 09, 2005 7:03 = PM
To: = psn-l@..............
Subject: Iris Waveform = Chart

 

PSN--thanks for the Iris Waveform Chart for the 9.0 = Sumatra=   = 12/26/04 event.  The surface = wave arrivals of multiple stations exhibited by distance, and text,  = makes a super graphic.  I was wondering about  the occurrence of a = seismic caustic at the appropriate degree distance.  Was the gap at 160 = degree area due to no reporting station near the "caustic" = distance.  In periodic recording here we've copied three caustics  in 20 = years--I believe the events were southwest of = Australia<= b> for us--not a very hot = spot.

    The 18 sec long period system at James Madison Un.  (Virginia) = working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) nicely, = but the 9.0 event read 20 min after P-diff arrived and then went off scale for = 100 minutes and returned to normal recording for the 7.1 event at = 04:21.  One can conclude, surface wave arrivals for us (at approx. 145 degrees) were obscured.  Keep up the good = work.

    &nbs= p;       Jim Lehman

Subject: RE: Iris Waveform Chart From: John or Jan Lahr johnjan@........ Date: Sun, 06 Feb 2005 17:13:23 -0800 Tim,

My understanding is that a caustic is formed when the derivative of Distance with
Take-off angle is zero.  ("Distance" is the angular distance from the earthquake
to the place where the ray reaches the surface of the Earth and Take-off angle
measures the direction with respect to vertical that the ray leaves the earthquake
source.)

Other cases of constructive interference are not termed caustics as far as I
know.  I'm traveling now, so can't refer to any seismology books and have
yet to find a good explanation on a web site. 

Maybe John Taber or Alan Jones can double check me on this!

Cheers,
John

At 04:15 PM 2/6/2005, you wrote:
So, is the term Caustic used only for the special case of the constructive interference at 155-degrees (or 144) or is it used for any case of constructive interference?


X-Originating-IP: [64.21.22.120]
From: "Connie and Jim Lehman" <lehmancj@...........>
To: <psn-l@..............>
Subject: Re: Iris Waveform Chart
Date: Sun, 6 Feb 2005 18:17:50 -0500
X-Mailer: Microsoft Outlook Express 5.50.4133.2400
Reply-To: psn-l@..............
Sender: psn-l-request@..............

Tim & others-
 
According to Bath, Intro. to Seismology, the author explains a seismic caustic as follows.  In a model of Earth with Core 1/2 dia. of the Earth Sphere, and a ratio of density l:1.2, every point situated more than 155 degrees from the surface event will receive not one but two PKP waves which propigate along different paths.  Exactly at 155 degrees, these waves coincide and result in a great concentration of energy--or a Caustic. 
   For reasons not easily explained, this caustic --in real earth seismicity occurs at or near 144 degrees.  The net effect of the Caustic is a ring of PKP concentration 36 degrees away from the "antipode" of the event.  ( Remember direct P-waves observe quiet time from 103 to 144 degrees )
    Although I have never seen this demo, I understand a sphere of high density glass enclosed with a sphere of lower density glass will show a similar ring of lazer light entering the far side.  Of course acoustic caustics can be demonstrated.
   The few caustics noted here (long Period) have a signature very unique from the usual events of S. Pacific.  The front loading of P related waves are larger than any of the other wave fronts, expecially in deep events where surface waves are minimized.
   No doubt there are better explanations     (Thanks Jorma)  of  this seismic phenomenon.   Do the geometry of P energy through the Core, and one gets an idea of what is going on.
            &nbs= p;     Jim Lehman
----- Original Message -----
From: Timothy Carpenter
To: psn-l@..............=
Sent: Saturday, February 05, 2005 4:33 PM
Subject: RE: Iris Waveform Chart

I should probably know = =96 but I don't. What is the "caustic" distance? And for that= matter, what is the "caustic"?

Regards,
-Tim-
 

Timothy= Carpenter, P.E., Pres.,
GeoDynamics Consultants, Inc.
5043 Whitlow Ct.
Commerce Twp., Mi 48382
248-363-4529 (voice & fax)
248-766-1629 (cell)
geodynamics@...........= (primary)
geodynamics@.......= (secondary)

 

 

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@..............] On Behalf Of= Connie and Jim Lehman
Sent: Sunday, January 09, 2005 7:03 PM
To: psn-l@..............
Subject: Iris Waveform Chart
 

PSN--thanks for the Iris Waveform Chart for the 9.0= Sumatra  12/26/04 event.  The surface wave arrivals of multiple= stations exhibited by distance, and text,  makes a super= graphic.  I was wondering about  the occurrence of a seismic= caustic at the appropriate degree distance.  Was the gap at 160 degree= area due to no reporting station near the "caustic"= distance.  In periodic recording here we've copied three= caustics  in 20 years--I believe the events were southwest of= Australia for us--not a very hot spot.

    The 18 sec long period system at James Madison= Un.  (Virginia) working into a graphic readout read the 8.1 Macquarie= Is. event-(l2/23) nicely, but the 9.0 event read 20 min after P-diff= arrived and then went off scale for 100 minutes and returned to normal= recording for the 7.1 event at 04:21.  One can conclude, surface wave= arrivals for us (at approx. 145 degrees) were obscured.  Keep up the= good work.

            Jim= Lehman
Subject: SAC binary file headers From: "rem11560@............ rem11560@netzero.com Date: Mon, 7 Feb 2005 02:29:58 GMT Hi all, I occasionally download SAC binary event files from the IRIS web site, primarily to compare my waveforms with that recorded by the nearby PAL and FOR stations of the LDEO network. I then use WinQuake to convert them to PSN format. In an effort to understand and use the information contained in the SAC header, I wrote a utility that reads out the 133 elements of the header. Not many of these elements contain any information on a typical file, but there is still a lot of information that is not transferred by WinQuake to the converted PSN file, including event time and location and sensor calibration. Event time is not specifically given, but is given as an offset in seconds from the starting time of the file. There is a number in the SAC header labeled "SCALE", usually a very large number, which must have to do with the gain of the sensor. Can anyone explain to me how to use this number to calculate a number to enter in WinQuake for sensor sensitivity? I have come up with an empirical formula Sensitivity = 40 * (1.0 / SCALE) which seems to come close to what gives me the response I expect from PAL and FOR, based on my own outputs, but a formula like that really doesn't make much sense to me. I hope someone out there can explain the meaning of SCALE. Cheers, Bob ______________________________________________________________________ Speed up your surfing with NetZero HiSpeed. Now includes pop-up blocker! Only $14.95/month -visit http://www.netzero.com/surf to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Iris Waveform Chart From: "Timothy Carpenter" GeoDynamics@....... Date: Mon, 7 Feb 2005 00:26:39 -0500 John, Thanks for the response. Usually I've had excellent success finding information on the web using one or the other of the several search = engines. But this time, the only things that showed up were excerpts from professional papers where the authors presumed the reader had known what = a caustic was since kindergarten. :-) (Well, actually I had, but that was caustic soda.) -Tim- -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of John or Jan Lahr Sent: Sunday, February 06, 2005 8:13 PM To: psn-l@.............. Cc: taber@......... Alan Jones Subject: RE: Iris Waveform Chart =20 Tim, My understanding is that a caustic is formed when the derivative of = Distance with=20 Take-off angle is zero. ("Distance" is the angular distance from the earthquake=20 to the place where the ray reaches the surface of the Earth and Take-off angle=20 measures the direction with respect to vertical that the ray leaves the earthquake=20 source.) Other cases of constructive interference are not termed caustics as far = as I know. I'm traveling now, so can't refer to any seismology books and = have=20 yet to find a good explanation on a web site. =20 Maybe John Taber or Alan Jones can double check me on this! Cheers, John At 04:15 PM 2/6/2005, you wrote: So, is the term Caustic used only for the special case of the = constructive interference at 155-degrees (or 144) or is it used for any case of constructive interference? X-Originating-IP: [64.21.22.120]=20 From: "Connie and Jim Lehman" =20 To: =20 Subject: Re: Iris Waveform Chart=20 Date: Sun, 6 Feb 2005 18:17:50 -0500=20 X-Mailer: Microsoft Outlook Express 5.50.4133.2400=20 Reply-To: psn-l@................. Sender: psn-l-request@................. Tim & others- =20 According to Bath, Intro. to Seismology, the author explains a seismic caustic as follows. In a model of Earth with Core 1/2 dia. of the Earth Sphere, and a ratio of density l:1.2, every point situated more than 155 degrees from the surface event will receive not one but two PKP waves = which propigate along different paths. Exactly at 155 degrees, these waves coincide and result in a great concentration of energy--or a Caustic. =20 For reasons not easily explained, this caustic --in real earth = seismicity occurs at or near 144 degrees. The net effect of the Caustic is a ring = of PKP concentration 36 degrees away from the "antipode" of the event. ( Remember direct P-waves observe quiet time from 103 to 144 degrees ) Although I have never seen this demo, I understand a sphere of high density glass enclosed with a sphere of lower density glass will show a similar ring of lazer light entering the far side. Of course acoustic caustics can be demonstrated. The few caustics noted here (long Period) have a signature very = unique from the usual events of S. Pacific. The front loading of P related = waves are larger than any of the other wave fronts, expecially in deep events where surface waves are minimized. No doubt there are better explanations (Thanks Jorma) of this seismic phenomenon. Do the geometry of P energy through the Core, and = one gets an idea of what is going on. Jim Lehman ----- Original Message -----=20 From: Timothy Carpenter =20 To: psn-l@................. Sent: Saturday, February 05, 2005 4:33 PM Subject: RE: Iris Waveform Chart I should probably know =96 but I don't. What is the "caustic" distance? = And for that matter, what is the "caustic"? Regards, -Tim- =20 Timothy Carpenter, P.E., Pres., GeoDynamics Consultants, Inc. 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) =20 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Connie and Jim Lehman Sent: Sunday, January 09, 2005 7:03 PM To: psn-l@.............. Subject: Iris Waveform Chart =20 PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra 12/26/04 = event. The surface wave arrivals of multiple stations exhibited by distance, = and text, makes a super graphic. I was wondering about the occurrence of = a seismic caustic at the appropriate degree distance. Was the gap at 160 degree area due to no reporting station near the "caustic" distance. In periodic recording here we've copied three caustics in 20 years--I = believe the events were southwest of Australia for us--not a very hot spot. The 18 sec long period system at James Madison Un. (Virginia) = working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) nicely, = but the 9.0 event read 20 min after P-diff arrived and then went off scale = for 100 minutes and returned to normal recording for the 7.1 event at 04:21. One can conclude, surface wave arrivals for us (at approx. 145 degrees) = were obscured. Keep up the good work. Jim Lehman

John,

Thanks for the response. Usually = I've had excellent success finding information on the web using one or the other = of the several search engines. But this time, the only things that showed up = were excerpts from professional papers where the authors presumed the reader = had known what a caustic was since kindergarten. J (Well, actually = I had, but that was caustic soda.)

-Tim-

-----Original = Message-----
From: = psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of John or Jan Lahr
Sent: Sunday, February 06, 2005 8:13 PM
To: psn-l@..............=
Cc: taber@......... Alan = Jones
Subject: RE: Iris = Waveform Chart

 

Tim,

My understanding is that a caustic is formed when the derivative of = Distance with
Take-off angle is zero.  ("Distance" is the angular = distance from the earthquake
to the place where the ray reaches the surface of the Earth and Take-off = angle
measures the direction with respect to vertical that the ray leaves the earthquake
source.)

Other cases of constructive interference are not termed caustics as far = as I
know.  I'm traveling now, so can't refer to any seismology books = and have
yet to find a good explanation on a web site. 

Maybe John Taber or Alan Jones can double check me on this!

Cheers,
John

At 04:15 PM 2/6/2005, you wrote:

So, is the term = Caustic used only for the special case of the constructive interference at = 155-degrees (or 144) or is it used for any case of constructive = interference?



X-Originating-IP: [64.21.22.120]
From: "Connie and Jim Lehman" <lehmancj@...........> =
To: <psn-l@..............>
Subject: Re: Iris Waveform Chart
Date: Sun, 6 Feb 2005 18:17:50 -0500
X-Mailer: Microsoft Outlook Express 5.50.4133.2400
Reply-To: psn-l@..............
Sender: psn-l-request@..............

Tim & others-
 
According to Bath, Intro. to Seismology, = the author explains a seismic caustic as follows.  In a model of Earth = with Core 1/2 dia. of the Earth Sphere, and a ratio of density l:1.2, every = point situated more than 155 degrees from the surface event will receive not = one but two PKP waves which propigate along different paths.  Exactly at = 155 degrees, these waves coincide and result in a great concentration of = energy--or a Caustic. 
   For reasons not easily explained, this caustic --in real = earth seismicity occurs at or near 144 degrees.  The net effect of the = Caustic is a ring of PKP concentration 36 degrees away from the = "antipode" of the event.  ( Remember direct P-waves observe quiet time from 103 = to 144 degrees )
    Although I have never seen this demo, I understand a = sphere of high density glass enclosed with a sphere of lower density glass will = show a similar ring of lazer light entering the far side.  Of course = acoustic caustics can be demonstrated.
   The few caustics noted here (long Period) have a signature = very unique from the usual events of S. Pacific.  The front loading of P related waves are larger than any of the other wave fronts, expecially = in deep events where surface waves are minimized.
   No doubt there are better = explanations     (Thanks Jorma)  of  this seismic phenomenon.   Do the = geometry of P energy through the Core, and one gets an idea of what is going on.
            &= nbsp;     Jim Lehman

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

From: Timothy Carpenter

To: psn-l@..............

Sent: Saturday, February 05, = 2005 4:33 PM

Subject: RE: Iris Waveform Chart

I should probably know – but I = don't. What is the "caustic" distance? And for that matter, what is the "caustic"?

Regards,

-Tim-

 

Timothy Carpenter, P.E., Pres.,

GeoDynamics Consultants, = Inc.

5043 Whitlow Ct.

Commerce Twp., Mi 48382

248-363-4529 (voice & = fax)

248-766-1629 (cell)

geodynamics@........... (primary)

geodynamics@....... = (secondary)

 

 

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

From: = psn-l-request@.............. [mailto:psn-l-request@..............] On Behalf Of Connie and Jim Lehman

Sent: Sunday, January 09, 2005 7:03 PM

To: = psn-l@..............

Subject: Iris Waveform Chart

 

PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra  12/26/04 event.  The surface = wave arrivals of multiple stations exhibited by distance, and text,  = makes a super graphic.  I was wondering about  the occurrence of a = seismic caustic at the appropriate degree distance.  Was the gap at 160 = degree area due to no reporting station near the "caustic" distance.  = In periodic recording here we've copied three caustics  in 20 years--I believe the events were southwest of Australia for us--not a very hot = spot.

    The 18 sec long period system at James Madison Un.  (Virginia) = working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) nicely, = but the 9.0 event read 20 min after P-diff arrived and then went off scale for = 100 minutes and returned to normal recording for the 7.1 event at = 04:21.  One can conclude, surface wave arrivals for us (at approx. 145 degrees) were obscured.  Keep up the good work.

    &nbs= p;       Jim Lehman


Subject: Fwd: Re: Iris Waveform Chart From: John or Jan Lahr johnjan@........ Date: Sun, 06 Feb 2005 22:06:35 -0800 John Taber, below, points out two sources of information on caustics that are on the web. 

The upper set if figures on Paul Richards's page (second URL below) shows how caustics can develop when even when the velocity increases continuously with depth. 

The lower set of figures shows how a shadow zone and caustic are created when there is a low velocity zone.

Cheers,
John

Date: Sun, 6 Feb 2005 22:17:39 -0500
Subject: Re: Iris Waveform Chart
To: John or Jan Lahr <johnjan@........>
From: John Taber <taber@........>

John,

That is my understanding as well. It is a point where energy will be focused.  Rick Aster has a fairly complete explanation at www.ees.nmt.edu/Geop/Classes/GEOP523/Docs/rays2003.pdf  ..  One website which shows an example, but without defining it is http://www.ldeo.columbia.edu/~richards/ARhtml/add_to_Sec9.4.html. I had unsubscribed from the PSN list while I was away so your email reminded me to resubscribe.

John


On Sunday, February 6, 2005, at 08:13  PM, John or Jan Lahr wrote:

Tim,

My understanding is that a caustic is formed when the derivative of Distance with
Take-off angle is zero.  ("Distance" is the angular distance from the earthquake
to the place where the ray reaches the surface of the Earth and Take-off angle
measures the direction with respect to vertical that the ray leaves the earthquake
source.)

Other cases of constructive interference are not termed caustics as far as I
know.  I'm traveling now, so can't refer to any seismology books and have
yet to find a good explanation on a web site. 

Maybe John Taber or Alan Jones can double check me on this!

Cheers,
John
Subject: RE: Re: Iris Waveform Chart From: "Timothy Carpenter" GeoDynamics@....... Date: Mon, 7 Feb 2005 18:18:34 -0500 John & John, Thanks. I reviewed your two references and then found this one: http://wwwrses.anu.edu.au/seismology/SHon2002/sp4sw.pdf which has some revealing graphics as well. Based on some of the stuff I've been reading, it looks like a lot of = this work was done ca. 1911. It still seems remarkable that so much was = (could be) done prior to the advent of the computer. Regards, -Tim- =20 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of John or Jan Lahr Sent: Monday, February 07, 2005 1:07 AM To: psn-l@.............. Cc: taber@........ Subject: Fwd: Re: Iris Waveform Chart =20 John Taber, below, points out two sources of information on caustics = that are on the web. =20 The upper set if figures on Paul Richards's page (second URL below) = shows how caustics can develop when even when the velocity increases = continuously with depth. =20 The lower set of figures shows how a shadow zone and caustic are created when there is a low velocity zone. Cheers, John Date: Sun, 6 Feb 2005 22:17:39 -0500 Subject: Re: Iris Waveform Chart To: John or Jan Lahr From: John Taber John,=20 That is my understanding as well. It is a point where energy will be focused. Rick Aster has a fairly complete explanation at www.ees.nmt.edu/Geop/Classes/GEOP523/Docs/rays2003.pdf . One website = which shows an example, but without defining it is http://www.ldeo.columbia.edu/~richards/ARhtml/add_to_Sec9.4.html. I had unsubscribed from the PSN list while I was away so your email reminded = me to resubscribe.=20 John=20 On Sunday, February 6, 2005, at 08:13 PM, John or Jan Lahr wrote:=20 Tim,=20 My understanding is that a caustic is formed when the derivative of = Distance with=20 Take-off angle is zero. ("Distance" is the angular distance from the earthquake=20 to the place where the ray reaches the surface of the Earth and Take-off angle=20 measures the direction with respect to vertical that the ray leaves the earthquake=20 source.)=20 Other cases of constructive interference are not termed caustics as far = as I know. I'm traveling now, so can't refer to any seismology books and = have=20 yet to find a good explanation on a web site. =20 Maybe John Taber or Alan Jones can double check me on this!=20 Cheers,=20 John=20

John & John,

Thanks.

I reviewed your two references and = then found this one: http://w= wwrses.anu.edu.au/seismology/SHon2002/sp4sw.pdf which has some revealing graphics as well.

Based on some of the stuff I've = been reading, it looks like a lot of this work was done ca. 1911. It still = seems remarkable that so much was (could be) done prior to the advent of the computer.

Regards,

-Tim-

 

 

-----Original = Message-----
From: = psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of John or Jan Lahr
Sent: Monday, February 07, 2005 1:07 AM
To: = psn-l@..............
Cc: taber@........
Subject: Fwd: Re: Iris = Waveform Chart

 

John Taber, below, points out two sources of information on caustics that are on the web. 

The upper set if figures on Paul Richards's page (second URL below) = shows how caustics can develop when even when the velocity increases continuously = with depth. 

The lower set of figures shows how a shadow zone and caustic are created = when there is a low velocity zone.

Cheers,
John


Date: Sun, 6 Feb 2005 22:17:39 = -0500
Subject: Re: Iris Waveform Chart
To: John or Jan Lahr <johnjan@........>
From: John Taber <taber@........>

John,

That is my = understanding as well. It is a point where energy will be focused.  Rick Aster has a = fairly complete explanation at www.ees.nmt.edu/Geop/Classes/GEOP523/Docs/rays2003.pdf  ..  One website which shows an example, but without defining it is = http://www.ldeo.columbia.edu/~richards/ARhtml/add_to_Sec9.4.html. I had unsubscribed from the PSN list while I was away so your email = reminded me to resubscribe.

John


On Sunday, February 6, 2005, at 08:13  PM, John or Jan Lahr wrote: =


Tim,

My understanding is that a caustic is formed when the derivative of = Distance with
Take-off angle is zero.  ("Distance" is the angular = distance from the earthquake
to the place where the ray reaches the surface of the Earth and Take-off = angle
measures the direction with respect to vertical that the ray leaves the earthquake
source.)

Other cases of constructive interference are not termed caustics as far = as I
know.  I'm traveling now, so can't refer to any seismology books = and have
yet to find a good explanation on a web site. 

Maybe John Taber or Alan Jones can double check me on this!

Cheers,
John

Subject: Shape of vane or plunger in liquid damping systems From: Roger Sparks rsparks@.......... Date: Tue, 08 Feb 2005 16:34:39 -0800 Hello All, I am looking for some feedback on my thoughts on liquid damping systems for amateur seismometers. All of the liquid damping systems that I have seen use vanes or plungers. As a beginning amateur seismologist, I made a vertical seismometer and used a washer (about 1 1/2 inch in diameter) in liquid for a damping system. I adjusted the viscosity of the oil to get an return overshoot (past center) about as described in several build-it-yourself sources. As I gained experience with my instrument, I noticed that I was not detecting local quakes that I thought I should detect. (I live in Washington state and we have a lot of local quakes). From the literature, I learned that local quakes are higher frequency, so I guessed that my instrument and amplifier were not detecting or passing the higher frequency signals. I easily increased the pass band of the amplifier, but still very little signal from local quakes. Then I considered how the plunger of my damping system must be acting as a low pass filter due to the characteristics of fluid flow at higher velocities. I reasoned that the plunger must move a column of fluid at some velocity. A fluid moving at a velocity would contain some energy E = mass * velocity squared and divided by 2. I further reasoned that if the frequency doubled, then the distance traveled in a given time period would also double, and the velocity would also have to double. If that was correct, then the energy required to set the system into motion to move a unit distance, would increase by a factor of 4 when the frequency doubled. That is a characteristic of a low pass filter system. I further considered that I was using a large diameter plunger and expecting fluid to move from the bottom center of the disk to the top center each half cycle. That certainly could not happen at higher frequencies. I reasoned that the path length from bottom center to top center doubled if the plunger diameter doubled. A longer path would require that the fluid velocities would have to be greater if the displacement was equal for both large and small plungers. Again, stored energy in the fluid due to velocity would be energy E = mass * velocity squared and divided by 2. I reasoned that the two factors would compound if the frequency doubled. Thus comparing two dampers, one twice the diameter of the other, the larger diameter plunger would require 16 times the energy to move at a doubled frequency through a unit distance compared to the smaller plunger which only requires 4 times the energy to move through the same unit distance at the same doubled frequency. To test my ideas, I drilled several holes in my plunger, thinking that the center to center distance would drop dramatically. This occurred, and I began seeing a much improved response to local quakes. There was little change in response to more distance quakes. If a few holes helped, the ultimate would be to go to a vertical vane which would consist of thin plates parallel to the direction of intended motion. The cross section of the structure at right angles to the motion would be as small as possible. The damping then would have to come from drag or friction as the liquid moved along the smooth sides of the plates. From my text books, I noticed that if the flow was laminar, then the friction would be related only to velocity, not to velocity squared. While the flow was laminar, the friction would increase with frequency in a linear relationship. At larger movements and very high frequencies, the flow would be turbulent and the friction again would become related to the velocity squared. My parallel vane damper worked very well and now I observe local quakes frequently. There is still room for improvement with further reduction of the structure cross section and more care in making the plates flat and parallel. In writing this, I hope that others with a better theoretical knowledge about fluid flow will critique my logic for accuracy. Does a larger plunger really require 16 times the energy at doubled frequency compared to 4 times the energy for doubled frequency needed by the smaller (1/2 diameter) plunger? (to move the same displacement) Wishing all the best, Roger __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Shape of vane or plunger in liquid damping systems From: SW6079@....... Date: Tue, 8 Feb 2005 20:21:30 EST I have had excellent luck on my Lehman using Mobile One automotive oil!! Quite a bit of experimentation was necessary, however. I have had excellent luck on my Leh= man using Mobile One automotive oil!!   Quite a bit of experimenta= tion was necessary, however.  Subject: Re: Shape of vane or plunger in liquid damping systems From: ChrisAtUpw@....... Date: Tue, 8 Feb 2005 21:57:13 EST In a message dated 09/02/2005, rsparks@.......... writes: I am looking for some feedback on my thoughts on liquid damping systems for amateur seismometers. Hi Roger, Consider the following 1. The viscosity of oil varies by about an order of magnitude for every 20 C Deg change. It is NOT 'nearly constant', as one account claims. The variations over 'normal' ambient house temperatures are huge. 2. The viscous drag varies with the shear rate, making the response strongly frequency dependant. 3. It is not a linear dependance. YOU JUST DO NOT NEED THESE PROBLEMS ! For these reasons, professional equipment stopped using fluid damping in the 1940s to 1950s and now uses passive magnetic damping or active feedback magnetic damping. With the ready availability of inexpensive NdFeB magnets, it is simple and easy to make very efficient dampers, which are dead easy to adjust, using two soft iron backing plates with NS and SN opposing bar magnets and an overlapping Cu or soft Al vane. The damping is hardly effected at all by ambient temperature changes. 1"x1/2"x1/4" thick NdFeB bar magnets with the poles on the large face do the job very nicely. 1/4" to 3/8" thick mild steel backing plates are fine. The only waring is that you do need to clean up the magnet faces with gaffer tape before final assembly to remove any fine wiskers of magnetic material. Magnetic damping is cleaner, cheaper and easier than oil damping systems. Regards, Chris Chapman
In a message dated 09/02/2005, rsparks@.......... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I am=20 looking for some feedback on my thoughts on liquid damping systems
for= =20 amateur seismometers.
Hi Roger,
 
    Consider the following
 
    1. The viscosity of oil varies by about an orde= r of=20 magnitude for every 20 C Deg change. It is NOT 'nearly constant', as one acc= ount=20 claims. The variations over 'normal' ambient house temperatures are huge.
 
    2. The viscous drag varies with the shear rate,= =20 making the response strongly frequency dependant.
 
    3. It is not a linear dependance.
 
    YOU JUST DO NOT NEED THESE PROBLEMS ! For these= =20 reasons, professional equipment stopped using fluid damping in the 1940s to=20 1950s and now uses passive magnetic damping or active feedback magnetic=20 damping.
    With the ready availability of inexpensive NdFe= B=20 magnets, it is simple and easy to make very efficient dampers, w= hich=20 are dead easy to adjust,  using two soft iron backing plates = with=20 NS and SN opposing bar magnets and an overlapping Cu or soft Al vane. T= he=20 damping is hardly effected at all by ambient temperature changes.
    1"x1/2"x1/4" thick NdFeB bar magnets with the p= oles=20 on the large face do the job very nicely. 1/4" to 3/8" thick mild steel back= ing=20 plates are fine. The only waring is that you do need to clean up the magnet=20 faces with gaffer tape before final assembly to remove any fine wiskers of=20 magnetic material.
    Magnetic damping is cleaner, cheaper and=20 easier than oil damping systems.
 
    Regards,
 
    Chris Chapman
 Subject: ebay auction From: BOB BARNS royb1@........... Date: Sat, 12 Feb 2005 10:30:10 -0500 Hi, I nromally ignore books but this seemed esp. interesting: Geophysical Theory -mathematics, geophysics, seismology Item number: 4527222797 ends Feb 19 Bob Barns __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Drum Recorders From: "Steve Hammond" shammon1@............. Date: Sat, 12 Feb 2005 09:23:16 -0800 Most of you know I live in the Santa Cruz area. I have two drum recorders sitting in my garage that have the pin motors but are missing pens and you would need to fabricate a pin to get one to work. If anybody in the PSN group would like to have a drum recorder, please let me know, I'll give one (them) to you. They are very old and heavy and would cost a Z$$ to ship. Regards, Steve Hammond PSN San Jose, Aptos, CA __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Drum Recorders From: "Steve Hammond" shammon1@............. Date: Sat, 12 Feb 2005 09:23:16 -0800 Most of you know I live in the Santa Cruz area. I have two drum recorders sitting in my garage that have the pin motors but are missing pens and you would need to fabricate a pin to get one to work. If anybody in the PSN group would like to have a drum recorder, please let me know, I'll give one (them) to you. They are very old and heavy and would cost a Z$$ to ship. Regards, Steve Hammond PSN San Jose, Aptos, CA __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Thanks for comments From: Roger Sparks rsparks@.......... Date: Sat, 12 Feb 2005 12:55:53 -0800 Thanks to all for comments in response to my request regarding plungers in liquid damping systems. Some day (probably soon) I will undertake to change the liquid damping to magnetic eddy current damping. I think it will be cleaner, less frequency sensitive, and less temperature sensitive. Roger psn-l-digest-request@.............. wrote: >.------ ------ ------ ------ ------ ------ ------ ------ ------ ------. >| Message 1 | >'------ ------ ------ ------ ------ ------ ------ ------ ------ ------' >Subject: Shape of vane or plunger in liquid damping systems >From: Roger Sparks >Date: Tue, 08 Feb 2005 16:34:39 -0800 > >Hello All, > >I am looking for some feedback on my thoughts on liquid damping systems >for amateur seismometers. > >All of the liquid damping systems that I have seen use vanes or >plungers. As a beginning amateur seismologist, I made a vertical >seismometer and used a washer (about 1 1/2 inch in diameter) in liquid >for a damping system. I adjusted the viscosity of the oil to get an >return overshoot (past center) about as described in several >build-it-yourself sources. > >As I gained experience with my instrument, I noticed that I was not >detecting local quakes that I thought I should detect. (I live in >Washington state and we have a lot of local quakes). From the >literature, I learned that local quakes are higher frequency, so I >guessed that my instrument and amplifier were not detecting or passing >the higher frequency signals. I easily increased the pass band of the >amplifier, but still very little signal from local quakes. > >Then I considered how the plunger of my damping system must be acting as >a low pass filter due to the characteristics of fluid flow at higher >velocities. I reasoned that the plunger must move a column of fluid at >some velocity. A fluid moving at a velocity would contain some energy >E = mass * velocity squared and divided by 2. I further reasoned that >if the frequency doubled, then the distance traveled in a given time >period would also double, and the velocity would also have to double. >If that was correct, then the energy required to set the system into >motion to move a unit distance, would increase by a factor of 4 when the >frequency doubled. That is a characteristic of a low pass filter system. > >I further considered that I was using a large diameter plunger and >expecting fluid to move from the bottom center of the disk to the top >center each half cycle. That certainly could not happen at higher >frequencies. I reasoned that the path length from bottom center to top >center doubled if the plunger diameter doubled. A longer path would >require that the fluid velocities would have to be greater if the >displacement was equal for both large and small plungers. Again, stored >energy in the fluid due to velocity would be energy E = mass * velocity >squared and divided by 2. > >I reasoned that the two factors would compound if the frequency doubled. >Thus comparing two dampers, one twice the diameter of the other, the >larger diameter plunger would require 16 times the energy to move at a >doubled frequency through a unit distance compared to the smaller >plunger which only requires 4 times the energy to move through the same >unit distance at the same doubled frequency. > >To test my ideas, I drilled several holes in my plunger, thinking that >the center to center distance would drop dramatically. This occurred, >and I began seeing a much improved response to local quakes. There was >little change in response to more distance quakes. > >If a few holes helped, the ultimate would be to go to a vertical vane >which would consist of thin plates parallel to the direction of intended >motion. The cross section of the structure at right angles to the >motion would be as small as possible. The damping then would have to >come from drag or friction as the liquid moved along the smooth sides of >the plates. From my text books, I noticed that if the flow was laminar, >then the friction would be related only to velocity, not to velocity >squared. While the flow was laminar, the friction would increase with >frequency in a linear relationship. At larger movements and very high >frequencies, the flow would be turbulent and the friction again would >become related to the velocity squared. > >My parallel vane damper worked very well and now I observe local quakes >frequently. There is still room for improvement with further reduction >of the structure cross section and more care in making the plates flat >and parallel. > >In writing this, I hope that others with a better theoretical knowledge >about fluid flow will critique my logic for accuracy. Does a larger >plunger really require 16 times the energy at doubled frequency compared >to 4 times the energy for doubled frequency needed by the smaller (1/2 >diameter) plunger? (to move the same displacement) > >Wishing all the best, > >Roger > > > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Paper & Ink From: "'Kareem Lanier'" kareem@............. Date: Sun, 20 Feb 2005 20:40:07 -0800 Hello, I'm trying to locate more paper for my PS-2 Kinemtrics Drum Recorder. Can anyone recommend any good inexpensive sources? Also is anyone familiar with the PS-2 system? Kareem
Hello, I'm trying to locate more paper for my = PS-2=20 Kinemtrics Drum Recorder. Can anyone recommend any good inexpensive = sources?=20 Also is anyone familiar with the PS-2 system?
 
Kareem
= Subject: RE: Paper & Ink From: "Meredith Lamb" meredithlamb@............. Date: Sun, 20 Feb 2005 22:31:40 -0700 Kareem, Years ago.....I used to use the un-inked back sides of rolls of chart recording paper. I note E-Bay has 2 sellers of various quanities of 11" wide rolls of chart paper now. Eleven inch or so, is about the upper max width of alot of old chart recorders....it "might be" adoptable to your 13.5" drum...if...it doesn't actually use that entire width on the drum and/or you create acouple pen movement limiters on each side? Chart paper is pretty easy to "adopt" for use, and the paper quality is usually fairly high and smoother than normal paper. Take care, Meredith ----- Original Message ----- From: Kareem Lanier To: PSN-L@.............. Sent: 2/20/2005 9:37:16 PM Subject: Paper & Ink Hello, I'm trying to locate more paper for my PS-2 Kinemtrics Drum Recorder. Can anyone recommend any good inexpensive sources? Also is anyone familiar with the PS-2 system? Kareem
Kareem,
 
Years ago.....I used to use the un-inked back sides of rolls of chart recording paper.  I note
E-Bay has 2 sellers of various quanities of 11" wide rolls of chart paper now.  Eleven inch
or so, is about the upper max width of alot of old chart recorders....it "might be" adoptable
to your 13.5" drum...if...it doesn't actually use that entire width on the drum and/or you create
acouple pen movement limiters on each side?  Chart paper is pretty easy to "adopt" for use,
and the paper quality is usually fairly high and smoother than normal paper.
 
Take care, Meredith
 
----- Original Message -----
Sent: 2/20/2005 9:37:16 PM
Subject: Paper & Ink

Hello, I'm trying to locate more paper for my PS-2 Kinemtrics Drum Recorder. Can anyone recommend any good inexpensive sources? Also is anyone familiar with the PS-2 system?
 
Kareem
Subject: Microseism filter From: "Dave Nelson" davefnelson@....... Date: Wed, 23 Feb 2005 23:53:13 -0800 I have recently added a Russian ASMET -1V MET broadband seismometer to = my setup. As I live near the coast the microseism level was dominating = the noise backgrond to the extent that earthquakes of interest were = being lost in the " noise". The microseism spectrum is very distinct and = I felt its elimination would not seriously effect the earthquake = detection capability . I have developed a simple filter based on switched capacitor technology = that virtualy eliminates the microseism background. The filter has no = critical componants or capacitors and is tuned by a clock frequency. = The Q is 0.5 which gives roughly an octave bandwidth centered at 0.015 = hz or 6.6 seconds . Since the center frequncy is clock dependant it can = be shifted arbitarily but 6.6 seconds seems to work very well. The = filter is placed directly ahead of the A/D at the highest voltage swing = level in the system to avoid adding noise. Just two wires -- in and out = (plus power of course). The results are very good, the harmonic like signal from microseism is = gone and the effective signal to noise ratio of eathquakes is = significantly better. The spectrum has a deep null at 6.6 seconds = instead of a dominant peak . I know this kind of spectrum shaping can be easily done in software but = that is usually beyond the scope of an amateur or computer dum- dum like = me. The whole thing is two IC's and a 15 hz clock generator. ( 100 = times the center frequency) The Russian seismometer is truely amazing. Virtually plug and play -- = four wires ,no adjustments or critical setup. The respose is advertised = to 20 seconds but seems to respond well to over 100 seconds on the low = end and too well to be useful ,given the urban background noise ,at the = high frequency end. I have another swiched capacitor low pass filter = switchable to 5, 2.5 and 1.25 hz. to control the high end cutoff. My setup also includes 3 axes of short period based on HS-10-1 1 hz = seismometers that I found in a surplus store. I am using Amaseis and = experimenting with Seismowin for analysis and display. I am a retired aerospace engineer who spent too much of my career in = management and I am having a ball doing the seismology thing.Good to be = back doing some development and putting the old brain to work. I intend = to do some seismometer development as my next project -- I have some = ideas for some different ,but not outrageous, concepts which may ( or = may not ) work.=20 I would be glad to correspond with anyone interested in or commenting on = what I am doing. Dave Nelson ( California not New Zealand)
I have recently added a = Russian ASMET -1V MET=20 broadband seismometer to my setup. As I live near the coast the = microseism level=20 was dominating the noise backgrond to the extent that earthquakes of = interest=20 were being lost in the " noise". The microseism spectrum is very = distinct and I=20 felt  its elimination  would not seriously effect the = earthquake=20 detection capability .
 
 I have developed a simple filter = based on=20 switched capacitor technology that virtualy eliminates the microseism=20 background. The filter has no critical componants or  capacitors = and is=20 tuned by a clock frequency. The Q is 0.5 which gives roughly an = octave=20 bandwidth centered at 0.015 hz or 6.6 seconds . Since the center = frequncy is=20 clock dependant it can be shifted arbitarily but 6.6 seconds seems to = work very=20 well. The filter is placed directly ahead of the A/D at the highest = voltage=20 swing  level in the system to avoid adding noise.  Just two = wires --=20 in and out (plus power of course).
 
The results are very good, the harmonic = like signal=20 from microseism is gone and the effective signal to noise ratio of = eathquakes is=20 significantly better. The spectrum has a deep null at 6.6 seconds = instead=20 of a  dominant peak .
 
I know this kind of spectrum shaping = can be easily=20 done in software but that is usually beyond the scope of an amateur = or=20 computer dum- dum like me. The whole thing is  two IC's and a 15 hz = clock=20 generator. ( 100 times the center frequency)
 
The Russian seismometer is truely = amazing.=20 Virtually plug and play -- four wires ,no adjustments or critical setup. = The=20 respose is advertised to 20 seconds but seems to respond well to over = 100=20 seconds on the low end and too well to be useful ,given the=20 urban background noise ,at the high frequency end. I have another = swiched=20 capacitor low pass filter switchable to 5, 2.5 and 1.25 hz. to control = the high=20 end cutoff.
 
My setup also includes 3 axes of short = period based=20 on HS-10-1  1 hz seismometers that I found in a surplus store. I am = using=20 Amaseis and experimenting with Seismowin for analysis and = display.
 
I am a retired aerospace engineer who = spent too=20 much of my career in management and I am having a ball doing the = seismology=20 thing.Good to be back doing some development and putting the old brain = to work.=20 I intend to do some seismometer development as my next project -- I have = some=20 ideas for some different ,but not outrageous, concepts which = may ( or=20 may not ) work.
 
I would be glad to correspond with = anyone=20 interested in or commenting on what I am doing.
 
 
Dave Nelson   ( California = not New=20 Zealand)
Subject: RE: Microseism filter From: "Steve Hammond" shammon1@............. Date: Thu, 24 Feb 2005 01:13:23 -0800 Hi Dave, I would like to see a picture of the ASMET - 1V MET seismometer. It sound like an interesting system. I live near the beach myself, in Aptos near Santa Cruz, and the ocean microseisms area very distinct here most of the time. Do you happen to have a logic diagram of your filter you designed? It might be just the thing I need for my Lehman's. As for my setup, like you, I also have three HS-10's. I use Larry's WINSDR with a GPS clock and Winquake. I'm very happy with the hardware and the software. In the past, I used IBM 12-bit A/D boards and ran two AT systems. In it's day it was a good setup. If you want to take a look, my website is at http://pw2.netcom.com/~shammon1/psnsj.htm and you can see some pictures of my old system with the AT's installed. The Lehman's and HS-10 are in the photos. I'm working on some newer photos of the electronics and will have them up on the site in the next week or two. Regards, Steve Hammond PSN San Jose, Aptos CA -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of Dave Nelson Sent: Wednesday, February 23, 2005 11:53 PM To: PSN-L@.............. Subject: Microseism filter I have recently added a Russian ASMET -1V MET broadband seismometer to my setup. As I live near the coast the microseism level was dominating the noise backgrond to the extent that earthquakes of interest were being lost in the " noise". The microseism spectrum is very distinct and I felt its elimination would not seriously effect the earthquake detection capability . I have developed a simple filter based on switched capacitor technology that virtualy eliminates the microseism background. The filter has no critical componants or capacitors and is tuned by a clock frequency. The Q is 0.5 which gives roughly an octave bandwidth centered at 0.015 hz or 6.6 seconds . Since the center frequncy is clock dependant it can be shifted arbitarily but 6.6 seconds seems to work very well. The filter is placed directly ahead of the A/D at the highest voltage swing level in the system to avoid adding noise. Just two wires -- in and out (plus power of course). The results are very good, the harmonic like signal from microseism is gone and the effective signal to noise ratio of eathquakes is significantly better. The spectrum has a deep null at 6.6 seconds instead of a dominant peak . I know this kind of spectrum shaping can be easily done in software but that is usually beyond the scope of an amateur or computer dum- dum like me. The whole thing is two IC's and a 15 hz clock generator. ( 100 times the center frequency) The Russian seismometer is truely amazing. Virtually plug and play -- four wires ,no adjustments or critical setup. The respose is advertised to 20 seconds but seems to respond well to over 100 seconds on the low end and too well to be useful ,given the urban background noise ,at the high frequency end. I have another swiched capacitor low pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end cutoff. My setup also includes 3 axes of short period based on HS-10-1 1 hz seismometers that I found in a surplus store. I am using Amaseis and experimenting with Seismowin for analysis and display. I am a retired aerospace engineer who spent too much of my career in management and I am having a ball doing the seismology thing.Good to be back doing some development and putting the old brain to work. I intend to do some seismometer development as my next project -- I have some ideas for some different ,but not outrageous, concepts which may ( or may not ) work. I would be glad to correspond with anyone interested in or commenting on what I am doing. Dave Nelson ( California not New Zealand)
Hi=20 Dave, I would like to see a picture of the ASMET - 1V MET seismometer. = It sound=20 like an interesting system.  I live near the beach myself, in Aptos = near=20 Santa Cruz, and the ocean microseisms area very distinct here most of = the time.=20 Do you happen to have a logic diagram of your filter you designed? It = might be=20 just the thing I need for my Lehman's. As for my setup,=20 like you, I also have three HS-10's. I use Larry's WINSDR with a GPS = clock and=20 Winquake. I'm very happy with the hardware and the software. In the = past, I used=20 IBM 12-bit A/D boards and ran two AT systems. In it's day it was a good = setup.=20 If you want to take a look, my website is at http://pw2.netcom.com/= ~shammon1/psnsj.htm and=20 you can see some pictures of my old system with the AT's installed. = The=20 Lehman's and HS-10 are in the photos. I'm working on some newer photos = of the=20 electronics and will have them up on the site in the next week or=20 two.  
Regards, Steve Hammond PSN San Jose, Aptos = CA
-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of Dave=20 Nelson
Sent: Wednesday, February 23, 2005 11:53 = PM
To:=20 PSN-L@..............
Subject: Microseism = filter

I have recently added a = Russian ASMET -1V=20 MET broadband seismometer to my setup. As I live near the coast the = microseism=20 level was dominating the noise backgrond to the extent that = earthquakes of=20 interest were being lost in the " noise". The microseism spectrum is = very=20 distinct and I felt  its elimination  would not = seriously=20 effect the earthquake detection capability .
 
 I have developed a simple = filter based on=20 switched capacitor technology that virtualy eliminates the microseism=20 background. The filter has no critical componants or  capacitors = and is=20 tuned by a clock frequency. The Q is 0.5 which gives roughly an = octave=20 bandwidth centered at 0.015 hz or 6.6 seconds . Since the center = frequncy is=20 clock dependant it can be shifted arbitarily but 6.6 seconds seems to = work=20 very well. The filter is placed directly ahead of the A/D at the = highest=20 voltage swing  level in the system to avoid adding noise.  = Just two=20 wires -- in and out (plus power of course).
 
The results are very good, the = harmonic like=20 signal from microseism is gone and the effective signal to noise ratio = of=20 eathquakes is significantly better. The spectrum has a deep null = at 6.6=20 seconds instead of a  dominant peak .
 
I know this kind of spectrum shaping = can be=20 easily done in software but that is usually beyond the scope of = an=20 amateur or computer dum- dum like me. The whole thing is  two = IC's and a=20 15 hz clock generator. ( 100 times the center frequency)
 
The Russian seismometer is truely = amazing.=20 Virtually plug and play -- four wires ,no adjustments or critical = setup. The=20 respose is advertised to 20 seconds but seems to respond well to over = 100=20 seconds on the low end and too well to be useful ,given the=20 urban background noise ,at the high frequency end. I have another = swiched=20 capacitor low pass filter switchable to 5, 2.5 and 1.25 hz. to control = the=20 high end cutoff.
 
My setup also includes 3 axes of = short period=20 based on HS-10-1  1 hz seismometers that I found in a surplus = store. I am=20 using Amaseis and experimenting with Seismowin for analysis and=20 display.
 
I am a retired aerospace engineer who = spent too=20 much of my career in management and I am having a ball doing the = seismology=20 thing.Good to be back doing some development and putting the old brain = to=20 work. I intend to do some seismometer development as my next project = -- I have=20 some ideas for some different ,but not outrageous, concepts which = may ( or may not ) work.
 
I would be glad to correspond with = anyone=20 interested in or commenting on what I am doing.
 
 
Dave Nelson   ( California = not New=20 Zealand)
Subject: Re: Microseism filter From: "David H. Youden" dyouden@............. Date: Thu, 24 Feb 2005 07:07:13 -0500 Dave, Tell me more about your filter. I live on the East coast, and am troubled by the level of microseisms. I have messed a bit with switched capacitor circuits in the past, but for different purposes. Could you send a circuit diagram directly to me? Or point me to the chip you used so I can puzzle out my own filter. Dave... Dave Nelson wrote: > I have recently added a Russian ASMET -1V MET broadband seismometer to > my setup. As I live near the coast the microseism level was dominating > the noise backgrond to the extent that earthquakes of interest were > being lost in the " noise". The microseism spectrum is very distinct > and I felt its elimination would not seriously effect the earthquake > detection capability . > > I have developed a simple filter based on switched capacitor > technology that virtualy eliminates the microseism background. The > filter has no critical componants or capacitors and is tuned by a > clock frequency. The Q is 0.5 which gives roughly an octave bandwidth > centered at 0.015 hz or 6.6 seconds . Since the center frequncy is > clock dependant it can be shifted arbitarily but 6.6 seconds seems to > work very well. The filter is placed directly ahead of the A/D at the > highest voltage swing level in the system to avoid adding noise. > Just two wires -- in and out (plus power of course). > > The results are very good, the harmonic like signal from microseism is > gone and the effective signal to noise ratio of eathquakes is > significantly better. The spectrum has a deep null at 6.6 seconds > instead of a dominant peak . > > I know this kind of spectrum shaping can be easily done in software > but that is usually beyond the scope of an amateur or computer dum- > dum like me. The whole thing is two IC's and a 15 hz clock generator. > ( 100 times the center frequency) > > The Russian seismometer is truely amazing. Virtually plug and play -- > four wires ,no adjustments or critical setup. The respose is > advertised to 20 seconds but seems to respond well to over 100 seconds > on the low end and too well to be useful ,given the urban background > noise ,at the high frequency end. I have another swiched capacitor low > pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end > cutoff. > > My setup also includes 3 axes of short period based on HS-10-1 1 hz > seismometers that I found in a surplus store. I am using Amaseis and > experimenting with Seismowin for analysis and display. > > I am a retired aerospace engineer who spent too much of my career in > management and I am having a ball doing the seismology thing.Good to > be back doing some development and putting the old brain to work. I > intend to do some seismometer development as my next project -- I have > some ideas for some different ,but not outrageous, concepts which > may ( or may not ) work. > > I would be glad to correspond with anyone interested in or commenting > on what I am doing. > > > Dave Nelson ( California not New Zealand) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Microseism filter From: Bob Hancock Bob.Hancock@............ Date: Thu, 24 Feb 2005 07:24:38 -0700 I purchased a CME 4111 (previously called a CME 2123) Russian MET seismometer back in the spring of 2002. The unit had an advertised pass band of 60 seconds to 50 hz. I have experienced some problems with the instrument over the time that I have owned it. However, these problems have all been overcome and have not detracted from the overall usefulness of the instrument, and my pleasure with it. I particularly like the fact that it is a plug and play instrument and does not require a mass lock. The instrument also required the use of a differential receiver which Larry Cochrane was kind enough to put together. While checking with other folks, including some professional seismologists, I found they had reviewed the MET instruments and that there are some problems in maintaining the accurate calibration required of professional instruments. I have had to adjust the advertised sensitivity numbers to bring the instrument more in line with its current sensitivity. However for the overall study of seismic waves on all three channels, and seismology in general, it's a great instrument, and is virtually maintenance free. Overall, I have been impressed with the instrument. It is great as it does not require the periodic leveling adjustments of Lehman type instruments. I dug a hole in the front yard, and set a 12 inch square, 2 inch thick cement block in the ground. I covered the instrument with a plastic bag and covered that with dirt. The instrument is currently resting on the cement block doing its thing. It is an extremely sensitive instrument and I like it. I periodically have compared the wave forms received with nearby professional instruments and believe the instrument does a good job. Bob Hancock Tucson, AZ _____ From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Dave Nelson Sent: Thursday, February 24, 2005 00:53 To: PSN-L@.............. Subject: Microseism filter I have recently added a Russian ASMET -1V MET broadband seismometer to my setup. As I live near the coast the microseism level was dominating the noise backgrond to the extent that earthquakes of interest were being lost in the " noise". The microseism spectrum is very distinct and I felt its elimination would not seriously effect the earthquake detection capability . I have developed a simple filter based on switched capacitor technology that virtualy eliminates the microseism background. The filter has no critical componants or capacitors and is tuned by a clock frequency. The Q is 0.5 which gives roughly an octave bandwidth centered at 0.015 hz or 6.6 seconds . Since the center frequncy is clock dependant it can be shifted arbitarily but 6.6 seconds seems to work very well. The filter is placed directly ahead of the A/D at the highest voltage swing level in the system to avoid adding noise. Just two wires -- in and out (plus power of course). The results are very good, the harmonic like signal from microseism is gone and the effective signal to noise ratio of eathquakes is significantly better. The spectrum has a deep null at 6.6 seconds instead of a dominant peak . I know this kind of spectrum shaping can be easily done in software but that is usually beyond the scope of an amateur or computer dum- dum like me. The whole thing is two IC's and a 15 hz clock generator. ( 100 times the center frequency) The Russian seismometer is truely amazing. Virtually plug and play -- four wires ,no adjustments or critical setup. The respose is advertised to 20 seconds but seems to respond well to over 100 seconds on the low end and too well to be useful ,given the urban background noise ,at the high frequency end. I have another swiched capacitor low pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end cutoff. My setup also includes 3 axes of short period based on HS-10-1 1 hz seismometers that I found in a surplus store. I am using Amaseis and experimenting with Seismowin for analysis and display. I am a retired aerospace engineer who spent too much of my career in management and I am having a ball doing the seismology thing.Good to be back doing some development and putting the old brain to work. I intend to do some seismometer development as my next project -- I have some ideas for some different ,but not outrageous, concepts which may ( or may not ) work. I would be glad to correspond with anyone interested in or commenting on what I am doing. Dave Nelson ( California not New Zealand)

I purchased a CME 4111 (previously called a CME 2123) Russian MET seismometer back in the spring of 2002.  The unit had an advertised pass band of 60 seconds to 50 hz.  I have experienced some problems with the instrument over the time that I have owned it.  However, these problems have all been overcome and have not detracted from the overall usefulness of the instrument, and my pleasure with it.  I particularly like the fact that it is a plug and play instrument and does not require a mass lock.  The instrument also required the use of a differential receiver which Larry Cochrane was kind enough to put together.

 

While checking with other folks, including some professional seismologists, I found they had reviewed the MET instruments and that there are some problems in maintaining the accurate calibration required of professional instruments.  I have had to adjust the advertised sensitivity numbers to bring the instrument more in line with its current sensitivity.  However for the overall study of seismic waves on all three channels, and seismology in general, it’s a great instrument, and is virtually maintenance free.

 

Overall, I have been impressed with the instrument.  It is great as it does not require the periodic leveling adjustments of Lehman type instruments.  I dug a hole in the front yard, and set a 12 inch square, 2 inch thick cement block in the ground. I covered the instrument with a plastic bag and covered that with dirt.   The instrument is currently resting on the cement block doing its thing.  It is an extremely sensitive instrument and I like it.  I periodically have compared the wave forms received with nearby professional instruments and believe the instrument does a good job.

 

Bob Hancock

Tucson, AZ

 

From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Dave Nelson
Sent: Thursday, February 24, 2005 00:53
To: PSN-L@..............
Subject: Microseism filter

 

I have recently added a Russian ASMET -1V MET broadband seismometer to my setup. As I live near the coast the microseism level was dominating the noise backgrond to the extent that earthquakes of interest were being lost in the " noise". The microseism spectrum is very distinct and I felt  its elimination  would not seriously effect the earthquake detection capability .

 

 I have developed a simple filter based on switched capacitor technology that virtualy eliminates the microseism background. The filter has no critical componants or  capacitors and is tuned by a clock frequency. The Q is 0.5 which gives roughly an octave bandwidth centered at 0.015 hz or 6.6 seconds . Since the center frequncy is clock dependant it can be shifted arbitarily but 6.6 seconds seems to work very well. The filter is placed directly ahead of the A/D at the highest voltage swing  level in the system to avoid adding noise.  Just two wires -- in and out (plus power of course).

 

The results are very good, the harmonic like signal from microseism is gone and the effective signal to noise ratio of eathquakes is significantly better. The spectrum has a deep null at 6.6 seconds instead of a  dominant peak .

 

I know this kind of spectrum shaping can be easily done in software but that is usually beyond the scope of an amateur or computer dum- dum like me. The whole thing is  two IC's and a 15 hz clock generator. ( 100 times the center frequency)

 

The Russian seismometer is truely amazing. Virtually plug and play -- four wires ,no adjustments or critical setup. The respose is advertised to 20 seconds but seems to respond well to over 100 seconds on the low end and too well to be useful ,given the urban background noise ,at the high frequency end. I have another swiched capacitor low pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end cutoff.

 

My setup also includes 3 axes of short period based on HS-10-1  1 hz seismometers that I found in a surplus store. I am using Amaseis and experimenting with Seismowin for analysis and display.

 

I am a retired aerospace engineer who spent too much of my career in management and I am having a ball doing the seismology thing.Good to be back doing some development and putting the old brain to work. I intend to do some seismometer development as my next project -- I have some ideas for some different ,but not outrageous, concepts which may ( or may not ) work.

 

I would be glad to correspond with anyone interested in or commenting on what I am doing.

 

 

Dave Nelson   ( California not New Zealand)

Subject: Re: Microseism filter From: "Connie and Jim Lehman" lehmancj@........... Date: Thu, 24 Feb 2005 10:05:40 -0500 PSN & Davids/2 Regrets to hear of necessity to tune out microseisms. I have always considered them a friend,--they are always there--a quick check of system, performance-- and really quite entertaining as changes occur daily--sometimes hourly. Certainly in a classroom or a Science Center setting the presense of microseisms adds to the total picture of Earth activities. My location inland in Virginia about 100 miles from the Atlantic puts me in range of a host of activity on the Eastern Seaboard --based of course on long period performance that I havc used. Tropical storms show the moment they reach Florida and move northward to New England or North Atlantic-- and the normal flow of barometric highs & lows in the southeast to northeast trending storm tracks through VA. Then for whatever reason in summer months, microseismic amplitudes go low for weeks at a time--an opportunity to crank up the gain a bit. I try to keep microseisms about 1/4 in. in amplitude most of the time. Microseisms build to obnoxious amplitudes only as hurricanes move up the east coast usually east of us, and there have been times where I closed down recording for 10 hours or so. Perhaps you folks by oceanside locations have to live with more of this "pounding" a lot of the time. I am curious what affect filtering of microseisms would have on an earthquakes profile--expecially the first arrivals of P-waves that often don't appear to have periods too far removed from the cluster of 3-7sec periods of typical microseisms. ----- Original Message ----- From: "David H. Youden" To: Sent: Thursday, February 24, 2005 7:07 AM Subject: Re: Microseism filter > Dave, > > Tell me more about your filter. I live on the East coast, and am > troubled by the level of microseisms. I have messed a bit with switched > capacitor circuits in the past, but for different purposes. Could you > send a circuit diagram directly to me? Or point me to the chip you used > so I can puzzle out my own filter. > > Dave... > > Dave Nelson wrote: > > > I have recently added a Russian ASMET -1V MET broadband seismometer to > > my setup. As I live near the coast the microseism level was dominating > > the noise backgrond to the extent that earthquakes of interest were > > being lost in the " noise". The microseism spectrum is very distinct > > and I felt its elimination would not seriously effect the earthquake > > detection capability . > > > > I have developed a simple filter based on switched capacitor > > technology that virtualy eliminates the microseism background. The > > filter has no critical componants or capacitors and is tuned by a > > clock frequency. The Q is 0.5 which gives roughly an octave bandwidth > > centered at 0.015 hz or 6.6 seconds . Since the center frequncy is > > clock dependant it can be shifted arbitarily but 6.6 seconds seems to > > work very well. The filter is placed directly ahead of the A/D at the > > highest voltage swing level in the system to avoid adding noise. > > Just two wires -- in and out (plus power of course). > > > > The results are very good, the harmonic like signal from microseism is > > gone and the effective signal to noise ratio of eathquakes is > > significantly better. The spectrum has a deep null at 6.6 seconds > > instead of a dominant peak . > > > > I know this kind of spectrum shaping can be easily done in software > > but that is usually beyond the scope of an amateur or computer dum- > > dum like me. The whole thing is two IC's and a 15 hz clock generator. > > ( 100 times the center frequency) > > > > The Russian seismometer is truely amazing. Virtually plug and play -- > > four wires ,no adjustments or critical setup. The respose is > > advertised to 20 seconds but seems to respond well to over 100 seconds > > on the low end and too well to be useful ,given the urban background > > noise ,at the high frequency end. I have another swiched capacitor low > > pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end > > cutoff. > > > > My setup also includes 3 axes of short period based on HS-10-1 1 hz > > seismometers that I found in a surplus store. I am using Amaseis and > > experimenting with Seismowin for analysis and display. > > > > I am a retired aerospace engineer who spent too much of my career in > > management and I am having a ball doing the seismology thing.Good to > > be back doing some development and putting the old brain to work. I > > intend to do some seismometer development as my next project -- I have > > some ideas for some different ,but not outrageous, concepts which > > may ( or may not ) work. > > > > I would be glad to correspond with anyone interested in or commenting > > on what I am doing. > > > > > > Dave Nelson ( California not New Zealand) > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Microseism filter From: Bob Hancock Bob.Hancock@............ Date: Thu, 24 Feb 2005 08:41:55 -0700 One of the sources of microseism is wave action at shore lines. There is a public US Navy web site that gives current wave heights and projections from 12 hours to 144 hours, world wide. It is useful in seeing where the wave activity is when you see large microseisms. https://www.fnmoc.navy.mil/PUBLIC/WAM/all_glbl.html Bob Hancock -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Connie and Jim Lehman Sent: Thursday, February 24, 2005 08:06 To: psn-l@.............. Subject: Re: Microseism filter PSN & Davids/2 Regrets to hear of necessity to tune out microseisms. I have always considered them a friend,--they are always there--a quick check of system, performance-- and really quite entertaining as changes occur daily--sometimes hourly. Certainly in a classroom or a Science Center setting the presense of microseisms adds to the total picture of Earth activities. My location inland in Virginia about 100 miles from the Atlantic puts me in range of a host of activity on the Eastern Seaboard --based of course on long period performance that I havc used. Tropical storms show the moment they reach Florida and move northward to New England or North Atlantic-- and the normal flow of barometric highs & lows in the southeast to northeast trending storm tracks through VA. Then for whatever reason in summer months, microseismic amplitudes go low for weeks at a time--an opportunity to crank up the gain a bit. I try to keep microseisms about 1/4 in. in amplitude most of the time. Microseisms build to obnoxious amplitudes only as hurricanes move up the east coast usually east of us, and there have been times where I closed down recording for 10 hours or so. Perhaps you folks by oceanside locations have to live with more of this "pounding" a lot of the time. I am curious what affect filtering of microseisms would have on an earthquakes profile--expecially the first arrivals of P-waves that often don't appear to have periods too far removed from the cluster of 3-7sec periods of typical microseisms. ----- Original Message ----- From: "David H. Youden" To: Sent: Thursday, February 24, 2005 7:07 AM Subject: Re: Microseism filter > Dave, > > Tell me more about your filter. I live on the East coast, and am > troubled by the level of microseisms. I have messed a bit with switched > capacitor circuits in the past, but for different purposes. Could you > send a circuit diagram directly to me? Or point me to the chip you used > so I can puzzle out my own filter. > > Dave... > > Dave Nelson wrote: > > > I have recently added a Russian ASMET -1V MET broadband seismometer to > > my setup. As I live near the coast the microseism level was dominating > > the noise backgrond to the extent that earthquakes of interest were > > being lost in the " noise". The microseism spectrum is very distinct > > and I felt its elimination would not seriously effect the earthquake > > detection capability . > > > > I have developed a simple filter based on switched capacitor > > technology that virtualy eliminates the microseism background. The > > filter has no critical componants or capacitors and is tuned by a > > clock frequency. The Q is 0.5 which gives roughly an octave bandwidth > > centered at 0.015 hz or 6.6 seconds . Since the center frequncy is > > clock dependant it can be shifted arbitarily but 6.6 seconds seems to > > work very well. The filter is placed directly ahead of the A/D at the > > highest voltage swing level in the system to avoid adding noise. > > Just two wires -- in and out (plus power of course). > > > > The results are very good, the harmonic like signal from microseism is > > gone and the effective signal to noise ratio of eathquakes is > > significantly better. The spectrum has a deep null at 6.6 seconds > > instead of a dominant peak . > > > > I know this kind of spectrum shaping can be easily done in software > > but that is usually beyond the scope of an amateur or computer dum- > > dum like me. The whole thing is two IC's and a 15 hz clock generator. > > ( 100 times the center frequency) > > > > The Russian seismometer is truely amazing. Virtually plug and play -- > > four wires ,no adjustments or critical setup. The respose is > > advertised to 20 seconds but seems to respond well to over 100 seconds > > on the low end and too well to be useful ,given the urban background > > noise ,at the high frequency end. I have another swiched capacitor low > > pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end > > cutoff. > > > > My setup also includes 3 axes of short period based on HS-10-1 1 hz > > seismometers that I found in a surplus store. I am using Amaseis and > > experimenting with Seismowin for analysis and display. > > > > I am a retired aerospace engineer who spent too much of my career in > > management and I am having a ball doing the seismology thing.Good to > > be back doing some development and putting the old brain to work. I > > intend to do some seismometer development as my next project -- I have > > some ideas for some different ,but not outrageous, concepts which > > may ( or may not ) work. > > > > I would be glad to correspond with anyone interested in or commenting > > on what I am doing. > > > > > > Dave Nelson ( California not New Zealand) > > __________________________________________________________ > > 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) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Microseisms and the need for PSN to look closer From: Col Lynam lynam@................ Date: Fri, 25 Feb 2005 08:51:38 +1000 Dear PSN networkers, FYI; check out this story on Moon-quake analysis and a retro study yielding new conclusions AND the value of keeping our seismograms archived and preserved properly February 15, 2005 (NYT) Scientists Find Deeper Meaning for Moon Rumblings http://www.nytimes.com/2005/02/15/science/space/15moon.html?ex=1109221200&en=ccd4da907f98d966&ei=5070 I agree with the previous 2 contributors - Microseisms are not just "noise', they tell a story about our ocean/ weather environment and perhaps, we should be more closely logging the amplitude/ frequency (6 hourly) to see the effect of the "greenhouse phenomena" and comparing it to similar months, say 10 years ago. Historically speaking (pre radar) microseismic measurements were the forecaster for trcking Cyclones and hurricanes. With rising sea levels (increased water mass), perhaps the oceans will change their resonant frquency (7hz) ??? Perhaps PSN "amateur seismologists" could keep a watch on that? Just some thoughts...I find the pSN network is a great experimenter; something that is lost these days where everything seismological seems to be done on a VDU and off-the-shelf instrumentation kills experimentation. cheers col lynam volunteer observor, QUAKES group, ESSCC centre, University of Queensland, Australia http://www.esscc.uq.edu.au Bob Hancock wrote: >One of the sources of microseism is wave action at shore lines. There is a >public US Navy web site that gives current wave heights and projections from >12 hours to 144 hours, world wide. It is useful in seeing where the wave >activity is when you see large microseisms. > > https://www.fnmoc.navy.mil/PUBLIC/WAM/all_glbl.html > >Bob Hancock > > >-----Original Message----- >From: psn-l-request@.............. [mailto:psn-l-request@............... On >Behalf Of Connie and Jim Lehman >Sent: Thursday, February 24, 2005 08:06 >To: psn-l@.............. >Subject: Re: Microseism filter > >PSN & Davids/2 > Regrets to hear of necessity to tune out microseisms. I have always >considered them a friend,--they are always there--a quick check of system, >performance-- and really quite entertaining as changes occur >daily--sometimes hourly. Certainly in a classroom or a Science Center >setting the presense of microseisms adds to the total picture of Earth >activities. My location inland in Virginia about 100 miles >from the Atlantic puts me in range of a host of activity on the Eastern >Seaboard --based of course on long period performance that I havc used. >Tropical storms show the moment they reach Florida and move northward to New >England or North Atlantic-- and the normal flow of barometric highs & lows >in the southeast to northeast trending storm tracks through VA. Then for >whatever reason in summer months, microseismic amplitudes go low for weeks >at a time--an opportunity to crank up the gain a bit. I try to keep >microseisms about 1/4 in. in amplitude most of the time. > Microseisms build to obnoxious amplitudes only as hurricanes move up the >east coast usually east of us, and there have been times where I closed down >recording for 10 hours or so. Perhaps you folks by oceanside locations have >to live with more of this "pounding" a lot of the time. > I am curious what affect filtering of microseisms would have on an >earthquakes profile--expecially the first arrivals of P-waves that often >don't appear to have periods too far removed from the cluster of 3-7sec >periods of typical microseisms. >----- Original Message ----- >From: "David H. Youden" >To: >Sent: Thursday, February 24, 2005 7:07 AM >Subject: Re: Microseism filter > > > > >>Dave, >> >>Tell me more about your filter. I live on the East coast, and am >>troubled by the level of microseisms. I have messed a bit with switched >>capacitor circuits in the past, but for different purposes. Could you >>send a circuit diagram directly to me? Or point me to the chip you used >>so I can puzzle out my own filter. >> >>Dave... >> >>Dave Nelson wrote: >> >> >> >>>I have recently added a Russian ASMET -1V MET broadband seismometer to >>>my setup. As I live near the coast the microseism level was dominating >>>the noise backgrond to the extent that earthquakes of interest were >>>being lost in the " noise". The microseism spectrum is very distinct >>>and I felt its elimination would not seriously effect the earthquake >>>detection capability . >>> >>> I have developed a simple filter based on switched capacitor >>>technology that virtualy eliminates the microseism background. The >>>filter has no critical componants or capacitors and is tuned by a >>>clock frequency. The Q is 0.5 which gives roughly an octave bandwidth >>>centered at 0.015 hz or 6.6 seconds . Since the center frequncy is >>>clock dependant it can be shifted arbitarily but 6.6 seconds seems to >>>work very well. The filter is placed directly ahead of the A/D at the >>>highest voltage swing level in the system to avoid adding noise. >>>Just two wires -- in and out (plus power of course). >>> >>>The results are very good, the harmonic like signal from microseism is >>>gone and the effective signal to noise ratio of eathquakes is >>>significantly better. The spectrum has a deep null at 6.6 seconds >>>instead of a dominant peak . >>> >>>I know this kind of spectrum shaping can be easily done in software >>>but that is usually beyond the scope of an amateur or computer dum- >>>dum like me. The whole thing is two IC's and a 15 hz clock generator. >>>( 100 times the center frequency) >>> >>>The Russian seismometer is truely amazing. Virtually plug and play -- >>>four wires ,no adjustments or critical setup. The respose is >>>advertised to 20 seconds but seems to respond well to over 100 seconds >>>on the low end and too well to be useful ,given the urban background >>>noise ,at the high frequency end. I have another swiched capacitor low >>>pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end >>>cutoff. >>> >>>My setup also includes 3 axes of short period based on HS-10-1 1 hz >>>seismometers that I found in a surplus store. I am using Amaseis and >>>experimenting with Seismowin for analysis and display. >>> >>>I am a retired aerospace engineer who spent too much of my career in >>>management and I am having a ball doing the seismology thing.Good to >>>be back doing some development and putting the old brain to work. I >>>intend to do some seismometer development as my next project -- I have >>>some ideas for some different ,but not outrageous, concepts which >>>may ( or may not ) work. >>> >>>I would be glad to correspond with anyone interested in or commenting >>>on what I am doing. >>> >>> >>>Dave Nelson ( California not New Zealand) >>> >>> >>__________________________________________________________ >> >>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 >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 >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. > > Dear PSN networkers,

FYI; check out this story on Moon-quake analysis and a retro study yielding new conclusions AND the value of keeping our seismograms archived and preserved properly
February 15, 2005 (NYT) Scientists Find Deeper Meaning for Moon Rumblings
http://www.nytimes.com/2005/02/15/science/space/15moon.html?ex=1109221200&en=ccd4da907f98d966&ei=5070

I agree with the previous 2 contributors - Microseisms are not just "noise', they tell a story about our ocean/ weather environment and perhaps, we should be more closely logging the amplitude/ frequency (6 hourly) to see the effect of the "greenhouse phenomena"  and comparing it to similar months, say 10 years ago.

Historically speaking (pre radar) microseismic measurements were the forecaster for trcking Cyclones and hurricanes.
With rising sea levels (increased water mass), perhaps the oceans will change their resonant frquency (7hz) ???
Perhaps PSN "amateur seismologists" could keep a watch on that?

Just some thoughts...I find the pSN network is a great experimenter; something that is lost these days where everything seismological seems to be done on a VDU and off-the-shelf instrumentation kills experimentation.

cheers
col lynam
volunteer observor, QUAKES group, ESSCC centre, University of Queensland, Australia
http://www.esscc.uq.edu.au


Bob Hancock wrote:
One of the sources of microseism is wave action at shore lines.  There is a
public US Navy web site that gives current wave heights and projections from
12 hours to 144 hours, world wide.  It is useful in seeing where the wave
activity is when you see large microseisms.

	https://www.fnmoc.navy.mil/PUBLIC/WAM/all_glbl.html

Bob Hancock


-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@..............] On
Behalf Of Connie and Jim Lehman
Sent: Thursday, February 24, 2005 08:06
To: psn-l@..............
Subject: Re: Microseism filter

PSN & Davids/2
     Regrets to hear of necessity to tune out microseisms.  I have always
considered them a friend,--they are always there--a quick check of system,
performance-- and really quite entertaining as changes occur
daily--sometimes hourly.  Certainly in a classroom or a Science Center
setting the presense of microseisms adds to the total picture of Earth
activities.  My location inland in Virginia about 100 miles
from the Atlantic puts me in range of a host of activity on the Eastern
Seaboard --based of course on long period performance that I havc used.
Tropical storms show the moment they reach Florida and move northward to New
England or North Atlantic--  and  the normal flow of barometric highs & lows
in the southeast to northeast trending storm tracks through VA.  Then for
whatever reason in summer months, microseismic amplitudes go low for weeks
at a time--an opportunity to crank up the gain a bit.  I try to keep
microseisms about 1/4 in. in amplitude most of the time.
    Microseisms build to obnoxious amplitudes only as hurricanes move up the
east coast usually east of us, and there have been times where I closed down
recording for 10 hours or so.  Perhaps you folks by oceanside locations have
to live with more of this "pounding" a lot of the time.
   I am curious what affect filtering of microseisms would have on an
earthquakes profile--expecially the first arrivals of P-waves that often
don't appear to have periods too far removed from the cluster of 3-7sec
periods of typical microseisms.
----- Original Message -----
From: "David H. Youden" <dyouden@.............>
To: <psn-l@..............>
Sent: Thursday, February 24, 2005 7:07 AM
Subject: Re: Microseism filter


  
Dave,

Tell me more about your filter. I live on the East coast, and am
troubled by the level of microseisms. I have messed a bit with switched
capacitor circuits in the past, but for different purposes. Could you
send a circuit diagram directly to me? Or point me to the chip you used
so I can puzzle out my own filter.

Dave...

Dave Nelson wrote:

    
I have recently added a Russian ASMET -1V MET broadband seismometer to
my setup. As I live near the coast the microseism level was dominating
the noise backgrond to the extent that earthquakes of interest were
being lost in the " noise". The microseism spectrum is very distinct
and I felt  its elimination  would not seriously effect the earthquake
detection capability .

 I have developed a simple filter based on switched capacitor
technology that virtualy eliminates the microseism background. The
filter has no critical componants or  capacitors and is tuned by a
clock frequency. The Q is 0.5 which gives roughly an octave bandwidth
centered at 0.015 hz or 6.6 seconds . Since the center frequncy is
clock dependant it can be shifted arbitarily but 6.6 seconds seems to
work very well. The filter is placed directly ahead of the A/D at the
highest voltage swing  level in the system to avoid adding noise.
Just two wires -- in and out (plus power of course).

The results are very good, the harmonic like signal from microseism is
gone and the effective signal to noise ratio of eathquakes is
significantly better. The spectrum has a deep null at 6.6 seconds
instead of a  dominant peak .

I know this kind of spectrum shaping can be easily done in software
but that is usually beyond the scope of an amateur or computer dum-
dum like me. The whole thing is  two IC's and a 15 hz clock generator.
( 100 times the center frequency)

The Russian seismometer is truely amazing. Virtually plug and play --
four wires ,no adjustments or critical setup. The respose is
advertised to 20 seconds but seems to respond well to over 100 seconds
on the low end and too well to be useful ,given the urban background
noise ,at the high frequency end. I have another swiched capacitor low
pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end
cutoff.

My setup also includes 3 axes of short period based on HS-10-1  1 hz
seismometers that I found in a surplus store. I am using Amaseis and
experimenting with Seismowin for analysis and display.

I am a retired aerospace engineer who spent too much of my career in
management and I am having a ball doing the seismology thing.Good to
be back doing some development and putting the old brain to work. I
intend to do some seismometer development as my next project -- I have
some ideas for some different ,but not outrageous, concepts which
may ( or may not ) work.

I would be glad to correspond with anyone interested in or commenting
on what I am doing.


Dave Nelson   ( California not New Zealand)
      
__________________________________________________________

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 
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 
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.
Subject: microseism filter From: "Dave Nelson" davefnelson@....... Date: Thu, 24 Feb 2005 17:09:48 -0800 >Hi Steve > > I am going to document the filter as soon as possible. I will send the > info to anyone who requests it . I also will give it to John Lahr for his > website. > > In short-- The filter is based on the National Semiconductor LMF100 dual > switched capacitor filter operating as bandpass in "mode 3" Both sections > are operated in parallel with the clocks 180 degrees out of phase to > cancel clock noise feedthrough. Both filer outputs are then subtracted > from the original signal in an op amp to produce the notch . I am ac > coupling with long time constants into the op amp summer to avoid offset > voltages. This may not be necessary if an offset adjustment is included at > the summing point. The 15 hz clock comes from a 30 hz CMOS gate > oscillator and a divide by two counter to get two phases with 50% duty > cycle.It could also come from the 60 hz power line divided by 4. The notch > center frequency is then 15/100 hz or 0.15 hz. > > The filter IC runs on +_ 5 volts and the op amp at +- 12 or 15 volts to > give the full swing for the a/d ( Dataq DI 154RS in my case). > > The microeseism signature is virtualy gone in the helicorder display and > the spectrum shows a notch where there was a peak. Nothing else seems > effected.. > > I'll get going with the documentation. > > The ASMET 1V is nothing more than a can about the size of a quart paint > can with a connector at the top. I have it covered with insulation and a > plastic dust cover so I can't get at it to get a photo--I'll do it next > time I go into the box.. > > I am running two copies of Amasies simultaneosly -- one short period > vertical and the other the wideband vertical. I like the program very much > but am always looking to try others that may be availabe . I am really new > at this so have a lot to learn. > > Best, > Dave Nelson > Palos Verdes Peninsula California > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: microseism filter From: "Dave Nelson" davefnelson@....... Date: Thu, 24 Feb 2005 17:38:46 -0800 I have had several comments regarding the the necessity or desirability = of filtring out microseism. It is always true that one persons "noise' = is anothers "data" I have also been fascinated by the microseism phenomenon itself and = have watched the effects of weather on the signature. I have also been = frustrated by the my attempts to extract earthquakes from the background = of the microseism. I value you comments and perspective. I need the = advice of those with exprience in this field. I look at this as an experiment and learning experience as I am NOT an = expert in this field. (I also have a switch to turn the filter off.) I have wondered about possible masking effects of true seismic event = signatures. In that context I have considered an automatic switch which = would turn off the filter when the level in the filter bandwidth becomes = suddenly larger than the long term average.Of course techniques like = that always have the problem of having the signal of intrest gone by the = time you recognize it I appreciate the comments and thank you for them. Dave Nelson
I have had several comments regarding = the the=20 necessity or desirability of filtring out microseism. It is always = true=20 that one persons "noise' is anothers "data"
 I have also been fascinated by = the microseism=20 phenomenon itself and have watched the effects of weather on the = signature. I=20 have also been frustrated by the my attempts to extract earthquakes from = the=20 background of the microseism. I value you comments and perspective. I = need the=20 advice of those with exprience in this field.
I look at this as an experiment and = learning=20 experience as I am NOT an expert in this field. (I also have a switch to = turn=20 the filter off.)
 
I have wondered about possible masking = effects of=20 true seismic event signatures. In that context I have considered an = automatic=20 switch which would turn off the filter when the level in the filter = bandwidth=20 becomes suddenly larger than the long term average.Of course techniques = like=20 that always have the problem of having the signal of intrest gone by the = time=20 you recognize it
 
I appreciate the comments and thank you = for=20 them.
 
Dave Nelson
Subject: Re: Microseism filter From: ChrisAtUpw@....... Date: Thu, 24 Feb 2005 22:13:44 EST In a message dated 24/02/2005, dyouden@............. writes: Tell me more about your filter. I live on the East coast, and am troubled by the level of microseisms. I have messed a bit with switched capacitor circuits in the past, but for different purposes. Could you send a circuit diagram directly to me? Or point me to the chip you used so I can puzzle out my own filter. Dave... Dave Nelson wrote: > > I have developed a simple filter based on switched capacitor > technology that virtualy eliminates the microseism background. The > filter has no critical componants or capacitors and is tuned by a > clock frequency. The Q is 0.5 which gives roughly an octave bandwidth > centered at 0.015 hz or 6.6 seconds . Since the center frequncy is > clock dependant it can be shifted arbitarily but 6.6 seconds seems to > work very well. The filter is placed directly ahead of the A/D at the > highest voltage swing level in the system to avoid adding noise. > Just two wires -- in and out (plus power of course). > > The results are very good, the harmonic like signal from microseism is > gone and the effective signal to noise ratio of eathquakes is > significantly better. The spectrum has a deep null at 6.6 seconds > instead of a dominant peak . > > I know this kind of spectrum shaping can be easily done in software > but that is usually beyond the scope of an amateur or computer dum- > dum like me. The whole thing is two IC's and a 15 hz clock generator. > ( 100 times the center frequency) > > I would be glad to correspond with anyone interested in or commenting > on what I am doing. > Dave Nelson Hi Dave, An alternative approach is to use a twin Tee bandstop filter. You need to sharpen the frequency response up quite a bit over a simple twin Tee circuit, which has a Q of about 0.2 ! You can make the Q variable by feeding the output into a unity gain opamp connected to a potentiometer to earth. You use a second unity gain opamp connected to the pot slider to provide the normal 'earth' connection of the twin Tee. Since you have to vary three resistors to change the frequency, it is easiest to use switched resistors. An alternative is to use potentiometers and set up the values with an Ohmmeter to suit your measured dominant period. You get a maximum reduction of a bit over 50 dB. They can also be useful if there is a local constant frequency vibration source. See also filter books for 'band stop' filter circuits and Linear LTC1043. Switched filters usually need a good low pass analogue filter on the output to reduce chopper noise and this can also significantly limit your low signal range. I prefer to use analogue filters - very low noise amplifiers do not mix too easily with digital circuits. You can expect to see different dominant periods depending on the nearest ocean or sea and to some extent on the changing weather conditions. The microseism amplitudes are strongly dependant on the ocean weather. It is relatively easy to filter out microseisms digitally with analysis programmes such as WinQuake. If you live right on the coast, filtering can be desirable, but otherwise they can provide a monitor for the proper operation of the sensors and may be interesting in themselves. Roberts published a circuit for extending the response of geophones to 1/10 the natural frequency. Regards, Chris Chapman
In a message dated 24/02/2005, dyouden@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Tell me=20 more about your filter. I live on the East coast, and am
troubled by t= he=20 level of microseisms. I have messed a bit with switched
capacitor circ= uits=20 in the past, but for different purposes. Could you
send a circuit diag= ram=20 directly to me? Or point me to the chip you used
so I can puzzle out m= y=20 own filter.

Dave...

Dave Nelson wrote:
>  >&nb= sp;=20 I have developed a simple filter based on switched capacitor
>=20 technology that virtualy eliminates the microseism background. The
>= ;=20 filter has no critical componants or  capacitors and is tuned by a=20
> clock frequency. The Q is 0.5 which gives roughly an octave bandw= idth=20
> centered at 0.015 hz or 6.6 seconds . Since the center frequncy i= s=20
> clock dependant it can be shifted arbitarily but 6.6 seconds seem= s to=20
> work very well. The filter is placed directly ahead of the A/D at= the=20
> highest voltage swing  level in the system to avoid adding=20 noise. 
> Just two wires -- in and out (plus power of=20 course).
> 
> The results are very good, the harmonic li= ke=20 signal from microseism is
> gone and the effective signal to noise=20 ratio of eathquakes is
> significantly better. The spectrum has a d= eep=20 null at 6.6 seconds
> instead of a  dominant peak .
>&nb= sp;=20
> I know this kind of spectrum shaping can be easily done in softwa= re=20
> but that is usually beyond the scope of an amateur or computer du= m-=20
> dum like me. The whole thing is  two IC's and a 15 hz clock=20 generator.
> ( 100 times the center frequency)
> 
&g= t; I=20 would be glad to correspond with anyone interested in or commenting
&g= t;=20 on what I am doing.
> Dave Nelson 
Hi Dave,
 
    An alternative approach is to use a twin Tee=20 bandstop filter. You need to sharpen the frequency response up quite a bit o= ver=20 a simple twin Tee circuit, which has a Q of about 0.2 ! You can make the Q=20 variable by feeding the output into a unity gain opamp connected to a=20 potentiometer to earth. You use a second unity gain opamp connected to the p= ot=20 slider to provide the normal 'earth' connection of the twin Tee. Since you h= ave=20 to vary three resistors to change the frequency, it is easiest to use=20 switched resistors. An alternative is to use potentiometers and set up the=20 values with an Ohmmeter to suit your measured dominant period. You get=20= a=20 maximum reduction of a bit over 50 dB. They can also be useful if there= is=20 a local constant frequency vibration source.
    See also filter books for 'band stop' filter=20 circuits and Linear LTC1043. Switched filters usually need a good low pass=20 analogue filter on the output to reduce chopper noise and this can also=20 significantly limit your low signal range. I prefer to use analogue fil= ters=20 - very low noise amplifiers do not mix too easily with digital=20 circuits.  
    You can expect to see different=20 dominant periods depending on the nearest ocean or sea and to some exte= nt=20 on the changing weather conditions. The microseism amplitudes are strongly=20 dependant on the ocean weather. 
    It is relatively easy to filter out microseisms= =20 digitally with analysis programmes such as WinQuake. If you live right on th= e=20 coast, filtering can be desirable, but otherwise they can provide a monitor=20= for=20 the proper operation of the sensors and may be interesting in themselves.
 
    Roberts published a circuit for extending the=20 response of geophones to 1/10 the natural frequency.
 
    Regards,
 
    Chris Chapman
 Subject: Re: microseism filter From: Dave Nelson davenn@............... Date: Fri, 25 Feb 2005 20:52:42 +1100 At 05:09 PM 24/02/2005 -0800, you wrote: Snip >>I am running two copies of Amasies simultaneosly -- one short period >>vertical and the other the wideband vertical. I like the program very >>much but am always looking to try others that may be availabe . I am >>really new at this so have a lot to learn. >>Best, >>Dave Nelson >>Palos Verdes Peninsula California Yoiu have no idea how weird it is to see ones own name on this list and knowing its some one else :) welcome to the group Dave, If you would like ur station data added to the ststion map and database please forward me the info in the format at the lower part of the www page http://www.sydneystormcity.com/calif.htm cheers from Sydney (ex New Zealand) Dave Nelson ( middle name ... Andrew) -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 266.4.0 - Release Date: 22/02/2005 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Microseisms and the need for PSN to look closer From: Jack Ivey ivey@.......... Date: Fri, 25 Feb 2005 10:01:17 -0500 There's a different way to look at seismic records that is particularly interesting for microseisms. For a long time I've been using the specgram function of Matlab to look at both microseisms and quakes. Specgram essentially divides the signal record into blocks of time and performs an FFT on each block. It then displays the FFT amplitude as a gray scale (or other color map). The Y axis of the display is increasing frequency, the X-axis is time, and brightness of each pixel corresponds to the amplitude of the signal at that time and frequency. Essentially you get an image showing how each frequency component changes with time. This type of display is frequently used in speech analysis, passive sonar, and probably other fields. This is not to be confused with the simple FFT function implemented by many of the data acquisition programs that gives a line of amplitude versus frequency, and which is useless by comparison. I was amazed at the different information available in this type of display compared with looking at a time series. You can see amplitude and frequency shifts of the microseisms (presumably as storms change location and intensity). You can see frequency shifts of the (dispersed) surface waves of a quake as it arrives. I have identified quakes by looking at the specgram display that I couldn't make out looking at the time series because they were buried in high-frequency noise. You can also see interesting higher-frequency signals, including line spectra that shift and come and go mysteriously (probably cultural noise of some type). The representation allows you to easily distinguish body and surface waves by their spectra, but because the FFT is done on blocks of data it is not useful for calculating very accurate arrival times. If anyone's interested I can dig out some old data and post a picture. It would be pretty easy to implement the algorithms in one of the data acquisition/display programs.... Jack __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Microseisms and the need for PSN to look closer From: John or Jan Lahr johnjan@........ Date: Fri, 25 Feb 2005 07:19:42 -0800 Hi Jack,

We used "spectrograms" of the sort that you described in studying the 1989-1990 eruption of Mt. Redoubt, Alaska.  They were the best method that we found to monitor and distinguish "LP" events (with emergent arrivals and lower frequency content) from "VT" events (volcano-tectonic events with higher-frequency content and sharp arrivals).  Swarms of LP events tended to precede eruptions.

It would be great to have a tool available to amateur seismologists and educators that would allow spectrograms to be easily generated.  Do you think this could be done without the use of Matlab?

Cheers,
John

At 07:01 AM 2/25/2005, you wrote:
There's a different way to look at seismic records that is particularly
interesting for microseisms.  For a long time I've been using the
specgram function of Matlab to look at both microseisms and quakes. 
Specgram essentially divides the signal record into blocks of time
and performs an FFT on each block.  It then displays the FFT amplitude
as a gray scale (or other color map).  The Y axis of the display is
increasing frequency, the X-axis is time, and brightness of each pixel
corresponds to the amplitude of the signal at that time and frequency.
Essentially you get an image showing how each frequency component changes
with time. 

This type of display is frequently used in speech analysis, passive sonar,
and probably other fields.  This is not to be confused with the simple
FFT function implemented by many of the data acquisition programs that
gives a line of amplitude versus frequency, and which is useless
by comparison. 

I was amazed at the different information available in this type
of display compared with looking at a time series.  You can see
amplitude and frequency shifts of the microseisms (presumably as
storms change location and intensity).  You can see frequency shifts
of the (dispersed) surface waves of a quake as it arrives. 
I have identified quakes by looking at the specgram display that I
couldn't make out looking at the time series because they were buried
in high-frequency noise.

You can also see interesting higher-frequency signals, including line
spectra that shift and come and go mysteriously (probably cultural noise
of some type).

The representation allows you to easily distinguish body and surface waves
by their spectra, but because the FFT is done on blocks of data it is
not useful for calculating very accurate arrival times.

If anyone's interested I can dig out some old data and post a picture.  It
would be pretty easy to implement the algorithms in one of the data
acquisition/display programs....

Jack

__________________________________________________________

Public Seismic Network Mailing List (PSN-L)

http://www.seismicnet.com/maillist.html for more information.


##################################/ John C. Lahr
#################################/ Emeritus Seismologist
################################/ U.S. Geological Survey
===========================/ Geologic Hazards Team, MS966
##############################/ PO Box 25046
#############################//##############################
############################//###############################
     Denver, Colorado 80225-0046 /################################
             Phone: (303) 215-9913 /=============================
               Fax: (303) 273-8540 /##################################
                     lahr@........ /###################################
                                          /####################################
                                 http://jclahr.com/science/
 Subject: RE: Microseisms and the need for PSN to look closer From: Jack Ivey ivey@.......... Date: Fri, 25 Feb 2005 10:28:36 -0500 John, Yes, the algorithms are published and not difficult. A nice user interface would be a bit of work, but it's definitely doable. Jack _____ From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of John or Jan Lahr Sent: Friday, February 25, 2005 10:20 AM To: psn-l@.............. Subject: RE: Microseisms and the need for PSN to look closer Hi Jack, We used "spectrograms" of the sort that you described in studying the 1989-1990 eruption of Mt. Redoubt, Alaska. They were the best method that we found to monitor and distinguish "LP" events (with emergent arrivals and lower frequency content) from "VT" events (volcano-tectonic events with higher-frequency content and sharp arrivals). Swarms of LP events tended to precede eruptions. It would be great to have a tool available to amateur seismologists and educators that would allow spectrograms to be easily generated. Do you think this could be done without the use of Matlab? Cheers, John At 07:01 AM 2/25/2005, you wrote: There's a different way to look at seismic records that is particularly interesting for microseisms. For a long time I've been using the specgram function of Matlab to look at both microseisms and quakes. Specgram essentially divides the signal record into blocks of time and performs an FFT on each block. It then displays the FFT amplitude as a gray scale (or other color map). The Y axis of the display is increasing frequency, the X-axis is time, and brightness of each pixel corresponds to the amplitude of the signal at that time and frequency. Essentially you get an image showing how each frequency component changes with time. This type of display is frequently used in speech analysis, passive sonar, and probably other fields. This is not to be confused with the simple FFT function implemented by many of the data acquisition programs that gives a line of amplitude versus frequency, and which is useless by comparison. I was amazed at the different information available in this type of display compared with looking at a time series. You can see amplitude and frequency shifts of the microseisms (presumably as storms change location and intensity). You can see frequency shifts of the (dispersed) surface waves of a quake as it arrives. I have identified quakes by looking at the specgram display that I couldn't make out looking at the time series because they were buried in high-frequency noise. You can also see interesting higher-frequency signals, including line spectra that shift and come and go mysteriously (probably cultural noise of some type). The representation allows you to easily distinguish body and surface waves by their spectra, but because the FFT is done on blocks of data it is not useful for calculating very accurate arrival times. If anyone's interested I can dig out some old data and post a picture. It would be pretty easy to implement the algorithms in one of the data acquisition/display programs.... Jack __________________________________________________________ Public Seismic Network Mailing List (PSN-L) for more information. ##################################/ John C. Lahr #################################/ Emeritus Seismologist ################################/ U.S. Geological Survey ===========================/ Geologic Hazards Team, MS966 ##############################/ PO Box 25046 #############################//############################## ############################//############################### Denver, Colorado 80225-0046 /################################ Phone: (303) 215-9913 /============================= Fax: (303) 273-8540 /################################## lahr@........ /################################### /#################################### http://jclahr.com/science/

John,

Yes, the algorithms are published = and not difficult.  A nice user interface would be a =

bit of work, but it’s = definitely doable.

 

=

Jack

 

=

 

=

From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of John or Jan Lahr
Sent: Friday, February = 25, 2005 10:20 AM
To: psn-l@..............
Subject: RE: Microseisms = and the need for PSN to look closer

 

Hi Jack,

We used "spectrograms" of the sort that you described in = studying the 1989-1990 eruption of Mt. = Redoubt, Alaska.  They were = the best method that we found to monitor and distinguish "LP" events = (with emergent arrivals and lower frequency content) from "VT" = events (volcano-tectonic events with higher-frequency content and sharp arrivals).  Swarms of LP events tended to precede eruptions.

It would be great to have a tool available to amateur seismologists and educators that would allow spectrograms to be easily generated.  = Do you think this could be done without the use of Matlab?

Cheers,
John

At 07:01 AM 2/25/2005, you wrote:

There's a different way to look at seismic records that is = particularly
interesting for microseisms.  For a long time I've been using the =
specgram function of Matlab to look at both microseisms and = quakes. 
Specgram essentially divides the signal record into blocks of time
and performs an FFT on each block.  It then displays the FFT = amplitude
as a gray scale (or other color map).  The Y axis of the display = is
increasing frequency, the X-axis is time, and brightness of each pixel =
corresponds to the amplitude of the signal at that time and = frequency.
Essentially you get an image showing how each frequency component = changes
with time. 

This type of display is frequently used in speech analysis, passive = sonar,
and probably other fields.  This is not to be confused with the = simple
FFT function implemented by many of the data acquisition programs = that
gives a line of amplitude versus frequency, and which is useless
by comparison. 

I was amazed at the different information available in this type
of display compared with looking at a time series.  You can see =
amplitude and frequency shifts of the microseisms (presumably as
storms change location and intensity).  You can see frequency = shifts
of the (dispersed) surface waves of a quake as it arrives. 
I have identified quakes by looking at the specgram display that I
couldn't make out looking at the time series because they were buried =
in high-frequency noise.

You can also see interesting higher-frequency signals, including line =
spectra that shift and come and go mysteriously (probably cultural = noise
of some type).

The representation allows you to easily distinguish body and surface = waves
by their spectra, but because the FFT is done on blocks of data it is =
not useful for calculating very accurate arrival times.

If anyone's interested I can dig out some old data and post a = picture.  It
would be pretty easy to implement the algorithms in one of the data
= acquisition/display programs....

Jack

__________________________________________________________

Public Seismic Network Mailing List (PSN-L)

eudora=3Dautourl>http://www.seismicnet.com/maillist.html for more information.


##################################/ John C. Lahr
#################################/ Emeritus Seismologist
################################/ U.S. Geological = Survey
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D/ Geologic Hazards Team, MS966
##############################/ PO Box 25046
#############################//##############################
############################//###############################
     Denver, Colorado 80225-0046 /################################
            = Phone: (303) 215-9913 = /=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D
            =    Fax: (303) 273-8540 /##################################
            =          lahr@........ /###################################
            =             =             =       /####################################
            =             =          http://jclahr.com/science/

Subject: RE: Microseisms and the need for PSN to look closer From: "James Hannon" jmhannon@......... Date: Fri, 25 Feb 105 09:53:54 CST I have used this program before. http://www.visualizationsoftware.com/gram.html It used to be free but you can still find older free versions on download sites. Jim Hannon ---------- Original Message ---------------------------------- From: John or Jan Lahr Reply-To: psn-l@.............. Date: Fri, 25 Feb 2005 07:19:42 -0800 > > >Hi Jack,

>We used "spectrograms" of the sort that you described in >studying the 1989-1990 eruption of Mt. Redoubt, Alaska. They were >the best method that we found to monitor and distinguish "LP" >events (with emergent arrivals and lower frequency content) from >"VT" events (volcano-tectonic events with higher-frequency >content and sharp arrivals). Swarms of LP events tended to precede >eruptions.

>It would be great to have a tool available to amateur seismologists and >educators that would allow spectrograms to be easily generated. Do >you think this could be done without the use of Matlab?

>Cheers,
>John

> -- Jim Hannon http://www.fmtcs.com/web/jmhannon/ 42,11.90N,91,39.26W WB0TXL -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Microseisms and the need for PSN to look closer From: "James Hannon" jmhannon@......... Date: Fri, 25 Feb 105 09:55:25 CST I have used this program before. http://www.visualizationsoftware.com/gram.html It used to be free but you can still find older free versions on download sites. Jim Hannon ---------- Original Message ---------------------------------- From: John or Jan Lahr Reply-To: psn-l@.............. Date: Fri, 25 Feb 2005 07:19:42 -0800 > > >Hi Jack,

>We used "spectrograms" of the sort that you described in >studying the 1989-1990 eruption of Mt. Redoubt, Alaska. They were >the best method that we found to monitor and distinguish "LP" >events (with emergent arrivals and lower frequency content) from >"VT" events (volcano-tectonic events with higher-frequency >content and sharp arrivals). Swarms of LP events tended to precede >eruptions.

>It would be great to have a tool available to amateur seismologists and >educators that would allow spectrograms to be easily generated. Do >you think this could be done without the use of Matlab?

>Cheers,
>John

> -- Jim Hannon http://www.fmtcs.com/web/jmhannon/ 42,11.90N,91,39.26W WB0TXL -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Microseisms and the need for PSN to look closer From: Mauro Mariotti mariotti@......... Date: Tue, 01 Feb 2005 16:45:56 +0100 Hello, i used spectrograms many times. I confirm that GRAM from Richard Horne is very well made fast and reliable. I applied a FFT for both graph and spectrograph JTF to seismowin it can be used also for noise comparison with the Peterson's noise curve widely recognized as a standard noise model. People using DATAQ board could benefit of this seismowin's tool. www.infoeq.it regards Mauro Mariotti At 16:53 25/02/2005, you wrote: >I have used this program before. >http://www.visualizationsoftware.com/gram.html > It used to be free but you can still find older free versions on > download sites. > >Jim Hannon > > >---------- Original Message ---------------------------------- >From: John or Jan Lahr >Reply-To: psn-l@.............. >Date: Fri, 25 Feb 2005 07:19:42 -0800 > > > > > > >Hi Jack,

> >We used "spectrograms" of the sort that you described in > >studying the 1989-1990 eruption of Mt. Redoubt, Alaska. They were > >the best method that we found to monitor and distinguish "LP" > >events (with emergent arrivals and lower frequency content) from > >"VT" events (volcano-tectonic events with higher-frequency > >content and sharp arrivals). Swarms of LP events tended to precede > >eruptions.

> >It would be great to have a tool available to amateur seismologists and > >educators that would allow spectrograms to be easily generated. Do > >you think this could be done without the use of Matlab?

> >Cheers,
> >John

> > >-- >Jim Hannon >http://www.fmtcs.com/web/jmhannon/ >42,11.90N,91,39.26W >WB0TXL >-- > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Microseisms and the need for PSN to look closer From: Larry Conklin lconklin@............ Date: Fri, 25 Feb 2005 11:04:52 -0500 Jack, I would love to hear more about this idea. I worked for many years in sonar development, so I have a pretty good idea of the merits of the technique. I don't have Matlab or anything comparable around here to try it. Sounds like a good software project. Larry Conklin Liverpool, NY Jack Ivey wrote: > There's a different way to look at seismic records that is particularly > interesting for microseisms. For a long time I've been using the > specgram function of Matlab to look at both microseisms and quakes. > Specgram essentially divides the signal record into blocks of time > and performs an FFT on each block. It then displays the FFT amplitude > as a gray scale (or other color map). The Y axis of the display is > increasing frequency, the X-axis is time, and brightness of each pixel > corresponds to the amplitude of the signal at that time and frequency. > Essentially you get an image showing how each frequency component changes > with time. > > This type of display is frequently used in speech analysis, passive sonar, > and probably other fields. This is not to be confused with the simple > FFT function implemented by many of the data acquisition programs that > gives a line of amplitude versus frequency, and which is useless > by comparison. > > I was amazed at the different information available in this type > of display compared with looking at a time series. You can see > amplitude and frequency shifts of the microseisms (presumably as > storms change location and intensity). You can see frequency shifts > of the (dispersed) surface waves of a quake as it arrives. > I have identified quakes by looking at the specgram display that I > couldn't make out looking at the time series because they were buried > in high-frequency noise. > > You can also see interesting higher-frequency signals, including line > spectra that shift and come and go mysteriously (probably cultural noise > of some type). > > The representation allows you to easily distinguish body and surface waves > by their spectra, but because the FFT is done on blocks of data it is > not useful for calculating very accurate arrival times. > > If anyone's interested I can dig out some old data and post a picture. It > would be pretty easy to implement the algorithms in one of the data > acquisition/display programs.... > > Jack > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Microseisms and the need for PSN to look closer From: Frank Gentges fgentges@.............. Date: Fri, 25 Feb 2005 11:12:39 -0500 Hi all, Reaching across the desk to my ham radio stuff, we have been using spectral analysis for very low speed CW on experimental LF communications/beacons. They have to resolve down to the sub-hertz region. A popular program, ARGO, that is free and runs on the PC is available for download at http://www.weaksignals.com/ Look at the ARGO page. Alberto, I2PHD and Vittorio, IK2CZL, have done a lot of work to make this software run on most PCs without a lot of special sound cards etc. The seismo data may have to be modulated with an audio tone to get the data within the passband of the sound card. It could prove useful for examining microseisms. Frank K0BRA Larry Conklin wrote: > Jack, > > I would love to hear more about this idea. I worked for many years in > sonar development, so I have a pretty good idea > of the merits of the technique. I don't have Matlab or anything > comparable around here to try it. Sounds like a good > software project. > > Larry Conklin > Liverpool, NY > > Jack Ivey wrote: > >> There's a different way to look at seismic records that is particularly >> interesting for microseisms. For a long time I've been using the >> specgram function of Matlab to look at both microseisms and quakes. >> Specgram essentially divides the signal record into blocks of time >> and performs an FFT on each block. It then displays the FFT >> amplitude as a gray scale (or other color map). The Y axis of the >> display is increasing frequency, the X-axis is time, and brightness >> of each pixel corresponds to the amplitude of the signal at that time >> and frequency. >> Essentially you get an image showing how each frequency component >> changes >> with time. > > Snip snip __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Microseisms and the need for PSN to look closer From: "James Hannon" jmhannon@......... Date: Fri, 25 Feb 105 10:37:55 CST Looks like SPECTRAN also at http://www.weaksignals.com/ Will read from both a sound card and a .wav file. No need to modulate anything just read a wav file. Jim Hannon ---------- Original Message ---------------------------------- From: Frank Gentges Reply-To: psn-l@.............. Date: Fri, 25 Feb 2005 11:12:39 -0500 >Hi all, > >Reaching across the desk to my ham radio stuff, we have been using >spectral analysis for very low speed CW on experimental LF >communications/beacons. They have to resolve down to the sub-hertz >region. A popular program, ARGO, that is free and runs on the PC is >available for download at > >http://www.weaksignals.com/ > -- Jim Hannon http://www.fmtcs.com/web/jmhannon/ 42,11.90N,91,39.26W WB0TXL -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: "The russians are coming!"...err..seismo's that is... From: "Meredith Lamb" meredithlamb@............. Date: Fri, 25 Feb 2005 15:07:07 -0700 Bob Hancock & (California) Dave Nelson, Yes....it would be very interesting to see the mechanical makeup of both of these seismometers; or, how they mechanically/electrically "tick". The only russian instrument on a search engine I found (article, with no pictures) was a electroylte model. I also get the impression that one or both of your russian acquisitions are perhaps portables? Verticals? Sensor type? I.E., the CME4111 or CME2123, and the ASMET -1V Take care, Meredith Lamb
Bob Hancock & (California) Dave Nelson,
 
Yes....it would be very interesting to see the mechanical makeup of both of these seismometers;
or, how they mechanically/electrically "tick".  The only russian instrument on a search engine I
found (article, with no pictures) was a electroylte model.  I also get the impression that one or
both of your russian acquisitions are perhaps portables? Verticals?  Sensor type?
 
I.E., the CME4111 or CME2123, and the ASMET -1V
 
Take care, Meredith Lamb
 
 
 
 
Subject: Test From: Col Lynam lynam@................ Date: Sat, 26 Feb 2005 08:45:31 +1000 My messages are not being posted?? col lynam Meredith Lamb wrote: > Bob Hancock & (California) Dave Nelson, > > Yes....it would be very interesting to see the mechanical makeup of > both of these seismometers; > or, how they mechanically/electrically "tick". The only russian > instrument on a search engine I > found (article, with no pictures) was a electroylte model. I also get > the impression that one or > both of your russian acquisitions are perhaps portables? Verticals? > Sensor type? > > I.E., the CME4111 or CME2123, and the ASMET -1V > > Take care, Meredith Lamb > > > > > > My messages are not being posted??
col lynam

Meredith Lamb wrote:
Bob Hancock & (California) Dave Nelson,
 
Yes....it would be very interesting to see the mechanical makeup of both of these seismometers;
or, how they mechanically/electrically "tick".  The only russian instrument on a search engine I
found (article, with no pictures) was a electroylte model.  I also get the impression that one or
both of your russian acquisitions are perhaps portables? Verticals?  Sensor type?
 
I.E., the CME4111 or CME2123, and the ASMET -1V
 
Take care, Meredith Lamb
 
 
 
 
Subject: Re: "The russians are coming!"...err..seismo's that is... From: ChrisAtUpw@....... Date: Fri, 25 Feb 2005 19:33:11 EST In a message dated 25/02/2005, meredithlamb@............. writes: Yes....it would be very interesting to see the mechanical makeup of both of these seismometers; or, how they mechanically/electrically "tick". The only russian instrument on a search engine I found (article, with no pictures) was a electroylte model. Hi Meredith, These are listed on the Princeton PEPP site. _http://lasker.princeton.edu/index.shtml_ (http://lasker.princeton.edu/index.shtml) _http://quake.eas.gatech.edu/Instruments/InstrumentSurvey.htm_ (http://quake.eas.gatech.edu/Instruments/InstrumentSurvey.htm) PMD is now at _http://www.eentec.com/_ (http://www.eentec.com/) They are electrolytic devices. Regards, Chris Chapman
In a message dated 25/02/2005, meredithlamb@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
Yes....it would be very interesting to see the mechanical makeup of b= oth=20 of these seismometers; or, how they mechanically/electrically "tick". = ;=20 The only russian instrument on a search engine I found (article, with no=20 pictures) was a electroylte model. 
Hi Meredith,
 
    These are listed on the Princeton PEPP site. http://lasker.princeton.edu= /index.shtml
    http:/= /quake.eas.gatech.edu/Instruments/InstrumentSurvey.htm
    PMD is now at http://www.eentec.com/
    They are electrolytic devices.
 
    Regards,
 
    Chris Chapman
 Subject: Re: Microseisms and the need for PSN to look closer From: ChrisAtUpw@....... Date: Fri, 25 Feb 2005 20:06:43 EST Hi there, =20 The Spectrum Lab data analysis programme is available from=20 _people.freenet.de/dl4yhf_ (http://people.freenet.de/dl4yhf) This can han= dle a wide=20 range of tasks, reading sound cards, wav files, ADCs.... Wolfgang B=FCscher= is very=20 helpful! =20 Regards, =20 Chris Chapman
Hi there,
 
    The Spectrum Lab data analysis programme is=20 available from people.freenet.de/dl4yhf =20= This=20 can handle a wide range of tasks, reading sound cards, wav files, ADCs.= ....=20 Wolfgang B=FCscher is very helpful!
 
    Regards,
 
    Chris Chapman
 Subject: Re: microseism filter From: Stephen & Kathy skmort@.......... Date: Sat, 26 Feb 2005 10:02:43 -0800 Speaking of AmaSies, is anyone running it with the DataQ DI-150RS??? The RS was the two channel Radio Shack version!! I've tried the two dataq options and while it does record somewhat, it does not record properly,,, the time advances at about twice the proper rate and at the end of each trace it goes through a strange iteration and drops about the last half of the record,, anything recorded in that last half is lost!!!! A few months ago I tried emailing the person who wrote it, but no response! If I can find a way to use it, I'd like to try it for awhile!! Thanks in advance for any help! You may email me directly at: skmort@.......... Stephen Mortensen PSN Station #55 near Pilot Hill Ca. USA 38.828N 120.979W >>> I am running two copies of Amasies simultaneosly -- one short period >>> vertical and the other the wideband vertical. I like the program very >>> much but am always looking to try others that may be availabe . I am >>> really new at this so have a lot to learn. >>> Best, >>> Dave Nelson >>> Palos Verdes Peninsula California > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: microseism filter From: Richard Gagnon richg_1998@......... Date: Sat, 26 Feb 2005 11:47:00 -0800 (PST) You might try this Yahoo Group. I use the 194 and I have received reponses to my questions. http://groups.yahoo.com/group/windaqdataacqsoftware/ Richard --- Stephen & Kathy wrote: > Speaking of AmaSies, is anyone running it with the DataQ DI-150RS??? > The RS was the two channel Radio Shack version!! I've tried the two > dataq options and while it does record somewhat, it does not record > properly,,, the time advances at about twice the proper rate and at > the end of each trace it goes through a strange iteration and drops > about the last half of the record,, anything recorded in that last half > is lost!!!! A few months ago I tried emailing the person who wrote it, > but no response! If I can find a way to use it, I'd like to try it for > awhile!! Thanks in advance for any help! > You may email me directly at: skmort@.......... > Stephen Mortensen > PSN Station #55 > near Pilot Hill Ca. USA > 38.828N 120.979W > > >>> I am running two copies of Amasies simultaneosly -- one short period > >>> vertical and the other the wideband vertical. I like the program very > >>> much but am always looking to try others that may be availabe . I am > >>> really new at this so have a lot to learn. > >>> Best, > >>> Dave Nelson > >>> Palos Verdes Peninsula California __________________________________ Do you Yahoo!? Yahoo! Mail - You care about security. So do we. http://promotions.yahoo.com/new_mail __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: microseism filter From: Mauro Mariotti mariotti@......... Date: Wed, 02 Feb 2005 21:09:21 +0100 Hello, I would be glad to add to Seismowin also the DATAQ DI-150 there is any guys that can send me that interface for 2 weeks to makeup the driver? Actually seismowin support the DI194. regards mauro At 20:47 26/02/2005, you wrote: >You might try this Yahoo Group. I use the 194 and I have received reponses to >my questions. > >http://groups.yahoo.com/group/windaqdataacqsoftware/ > >Richard > > > >--- Stephen & Kathy wrote: > > > Speaking of AmaSies, is anyone running it with the DataQ DI-150RS??? > > The RS was the two channel Radio Shack version!! I've tried the two > > dataq options and while it does record somewhat, it does not record > > properly,,, the time advances at about twice the proper rate and at > > the end of each trace it goes through a strange iteration and drops > > about the last half of the record,, anything recorded in that last half > > is lost!!!! A few months ago I tried emailing the person who wrote it, > > but no response! If I can find a way to use it, I'd like to try it for > > awhile!! Thanks in advance for any help! > > You may email me directly at: skmort@.......... > > Stephen Mortensen > > PSN Station #55 > > near Pilot Hill Ca. USA > > 38.828N 120.979W > > > > >>> I am running two copies of Amasies simultaneosly -- one short period > > >>> vertical and the other the wideband vertical. I like the program very > > >>> much but am always looking to try others that may be availabe . I am > > >>> really new at this so have a lot to learn. > > >>> Best, > > >>> Dave Nelson > > >>> Palos Verdes Peninsula California > > > > > >__________________________________ >Do you Yahoo!? >Yahoo! Mail - You care about security. So do we. >http://promotions.yahoo.com/new_mail >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Test From: Col Lynam lynam@................ Date: Sun, 27 Feb 2005 09:56:50 +1000 Thanks Chris, I am not "seeing" these at my end (posted 2 - seeing none). If the "moderator" is tuned in, can you check my member email address please and see if they're bouncing? Sorry for annoying everyone else. cheers col Lynam Volunteer Observor, QUAKES group, ESSCC Centre, Uni of Qld Australia http://www.esscc.uq.edu.au ChrisAtUpw@....... wrote: > In a message dated 25/02/2005 22:37:26 GMT Standard Time, > lynam@................ writes: > > My messages are not being posted?? > col lynam > > This one certainly got through! > > Regards, > > Chris Chapman Thanks Chris,
I am not "seeing" these at my end (posted 2 - seeing none).
If the "moderator" is tuned in, can you check my member email address please and see if they're bouncing?
Sorry for annoying everyone else.
cheers
col Lynam
Volunteer Observor, QUAKES group, ESSCC Centre, Uni of Qld Australia
http://www.esscc.uq.edu.au

ChrisAtUpw@....... wrote:
In a message dated 25/02/2005 22:37:26 GMT Standard Time, lynam@................ writes:
My messages are not being posted??
col lynam
This one certainly got through!
 
    Regards,
 
    Chris Chapman
Subject: Re: Test From: Mark Robinson mark.robinson@............... Date: Sun, 27 Feb 2005 13:16:36 +1300 Col Lynam wrote: > Thanks Chris, > I am not "seeing" these at my end (posted 2 - seeing none). > If the "moderator" is tuned in, can you check my member email address > please and see if they're bouncing? Hi Col, This list is slightly unusual in that mails you post to it are not returned to you, you may instead see an email that says something like "your mail has been received by the PSN-L list". regards Mark __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: microseism filter From: John or Jan Lahr johnjan@........ Date: Sat, 26 Feb 2005 17:27:43 -0800 Hi Stephen, I don't think that AmaSeis can handle two data streams from a single DATAQ AD. However, if you use two AD's and attach each to a different com port, then I believe you can run two copies of AmaSeis at the same time. Of course each copy must be run in it's own directory. Cheers, John Lahr At 10:02 AM 2/26/2005, you wrote: >Speaking of AmaSies, is anyone running it with the DataQ DI-150RS??? >The RS was the two channel Radio Shack version!! I've tried the two >dataq options and while it does record somewhat, it does not record >properly,,, the time advances at about twice the proper rate and at the >end of each trace it goes through a strange iteration and drops about the >last half of the record,, anything recorded in that last half is >lost!!!! A few months ago I tried emailing the person who wrote it, but >no response! If I can find a way to use it, I'd like to try it for >awhile!! Thanks in advance for any help! >You may email me directly at: skmort@.......... > Stephen Mortensen > PSN Station #55 > near Pilot Hill Ca. USA > 38.828N 120.979W > >>>>I am running two copies of Amasies simultaneosly -- one short period >>>>vertical and the other the wideband vertical. I like the program very >>>>much but am always looking to try others that may be availabe . I am >>>>really new at this so have a lot to learn. >>>>Best, >>>>Dave Nelson >>>>Palos Verdes Peninsula California >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with the body of the >message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Microseism filter From: "rem11560@............ rem11560@netzero.com Date: Sun, 27 Feb 2005 04:25:33 GMT For those of you who want to try notch filtering, why not experiment with the FFT notch filter in WinQuake? If you use analog filtering before A/D conversion, you will never know what the raw data looks like. My recommendation is to use an octave bandwidth, with the geometric mean of the high pass and low pass filters at the frequency you want to suppress. Suppose the period of the microseisms is 6 seconds, corresponding to 0.167 Hz. The upper frequency corner of the notch will then be 0.167 * 1.414 = 0.236 Hz. The lower frequency corner will be 0.167 / 1.414 = 0.118 Hz. I will leave it to you to experiment with the number of poles to use. The default 6 poles seems OK. Personally, I would not use notch filtering, as it can mask or distort the phases of the event. Bob McClure ______________________________________________________________________ Speed up your surfing with NetZero HiSpeed. Now includes pop-up blocker! Only $14.95/month -visit http://www.netzero.com/surf to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Switched Capacitor filters From: "Doug Crice" dcrice@............ Date: Sun, 27 Feb 2005 05:58:51 -0800 Switched capacitor filters are very nice to work with, easy to design = and control, but they have limited dynamic range, typically less than 80 dB. = Now that's a lot if you're just looking at an analog trace, but only = equivalent to a 12 or 13 bit A/D converter. If anybody is using a 16-bit or one of = the 24-bit delta-sigma converters, you should use digital filtering to = maintain your dynamic range. =20 Doug Crice Wireless Seismic http://www.wirelessSeismic.com 12996 Somerset Drive phone 1-530-274-4445 Grass Valley, CA 95945 USA fax 1-530-274-4446 =20

Switched capacitor filters are very nice to work = with, easy to design and control, but they have limited dynamic range, typically = less than 80 dB. Now that’s a lot if you’re just looking at an analog = trace, but only equivalent to a 12 or 13 bit A/D converter. If anybody is using = a 16-bit or one of the 24-bit delta-sigma converters, you should use = digital filtering to maintain your dynamic range.

 

Doug Crice

Wireless Seismic           = http://www.wirelessSeismic.com

12996 Somerset Drive       &nbs= p;        phone 1-530-274-4445

Grass Valley,  CA  95945  USA    fax = 1-530-274-4446

 

Subject: New subscriber From: John Popelish jpopelish@........ Date: Sun, 27 Feb 2005 15:48:22 -0500 I am a new subscriber to PSN-L and look forward to learning from, and perhaps, contributing to the group. I am an electrical engineer residing in the Shenandoah valley in central Virginia. Analog circuit design is my forte, but I have not been using it much for the last 20 something years of my career as an industrial maintenance and control consultant. I have been interested in geology, volcanism and earthquakes for a long time. After discussing seismometer amplifiers with someone, recently, in sci.electronics.design, I started searching the web for home built seismometer and sensor designs. One thing that struck me about many of the sensor designs is their lack of optimization and sophistication. Either this means that the sensor is not the limiting part of most designs or else it means that considerable improvement is possible. After puzzling a bit over how I might design an inductive sensor that would improve upon the simple solenoidal coil and horse shoe magnet approach, I think I have come up with a more sensitive design that also has noise canceling capability that will help it reject line generated fields (AC hum), variations in the Earth's magnetic field caused by the solar wind and lightning magnetic fields. This is based on making two similar coils that produce equal and opposite signals when exposed to large, common, external fields, but produce equal and aiding signals when exposed to the relative movement between the coils and magnet structure. The magnet structure also has no net external field to interact with the geo field that might interact with the seismometer boom. I have purchased a batch of NeFeB magnets on EBAY and am awaiting a quote for construction of the 6 iron pole pieces to make one of these fist sized sensors. I will make the coil forms and wind the coils, myself. I will also make the signal amplifier and filter. If that all comes together, I will take a shot at building a Lehman type horizontal, long period pendulum. I also have a DATAQ DI-194-RS to hook it up to a computer but no software other than what came with that unit. Eventually I want to add an optical beam sensor that will make the unit act as a tilt meter (true DC operation, similar to the differential capacitive bridge type pickup, but with much simpler support circuits) and allow experiments with feedback using the original inductive sensor as a linear motor. This should keep me busy for a year or more. I am looking forward to not only seeing signals from world wide seismic events, but seeing what local signals come through. Train traffic passes a few miles away in two directions. Your suggestions, questions, advice and comments are certainly welcome. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: New subscriber From: ChrisAtUpw@....... Date: Sun, 27 Feb 2005 22:52:33 EST In a message dated 27/02/2005, jpopelish@........ writes: I am an electrical engineer residing in the Shenandoah valley in central Virginia. Analog circuit design is my forte. I have been interested in geology, volcanism and earthquakes for a long time. After discussing seismometer amplifiers with someone, recently, in sci.electronics.design, I started searching the web for home built seismometer and sensor designs. One thing that struck me about many of the sensor designs is their lack of optimisation and sophistication. Either this means that the sensor is not the limiting part of most designs or else it means that considerable improvement is possible. Hi John, Welcome! I can't comment on your discussions - I can't find the website you quote. Seismometer amplifiers do need quite specialised design with low noise, low drift, high gain and good filters with a low pulse overshoot. I don't know where you are finding the 'many' amplifier designs? There is one on Larry's website which uses LT1007s and is optimised. You need to optimise both current and voltage noise sources. LT1007s, OP07s and OP27s can all give satisfactory performance. If you wish to use very long periods where 1/f noise is a limitation, MAX432 and chopper amp circuits are available. Don't confuse apparently simple with unsophisticated! You are trying to get the amplifier noise a factor of 10 lower than the seismic noise. The ready availability of inexpensive but powerful NdFeB magnets has allowed the use of smaller sensor coils and magnets with increased sensitivity. After puzzling a bit over how I might design an inductive sensor that would improve upon the simple solenoidal coil and horse shoe magnet approach, I think I have come up with a more sensitive design that also has noise cancelling capability that will help it reject line generated fields (AC hum), variations in the Earth's magnetic field caused by the solar wind and lightning magnetic fields. This is based on making two similar coils that produce equal and opposite signals when exposed to large, common, external fields, but produce equal and aiding signals when exposed to the relative movement between the coils and magnet structure. The magnet structure also has no net external field to interact with the geo field that might interact with the seismometer boom. I have purchased a batch of NeFeB magnets on EBAY and am awaiting a quote for construction of the 6 iron pole pieces to make one of these fist sized sensors. I will make the coil forms and wind the coils, myself. I will also make the signal amplifier and filter. If that all comes together, I will take a shot at building a Lehman type horizontal, long period pendulum. I suggest that you consider 1" square NdFeB magnets in a quad formation, NS opposing SN, in between two 1/4" thick rectangular mild steel plates, say 3.5" long by 2" wide. You wind a flat rectangular coil to half cover the magnet poles, say ~1" square. The coil is completely screened by the soft iron backing plates, which should be earthed to the same point as the seismometer frame and the amplifier inputs. You can use the same layout, but with thicker rectangular 1" x 1/2" magnets for an Al or Cu inductive damping plate. This design gives very low stray external magnetic fields. Try it - you will like it! AC hum is fairly low and is strongly filtered by your 3 to 10 Hz amplifier filters. You should use woven screen connecting cable. The main problem in domestic situations is in limiting interference coming in through the utility supply and from various domestic sources. Fridges, cookers and electrical heating systems can produce large surges. You may benefit from a line filter. It is preferable to make the seismometer arm and weight using non magnetic materials. Stainless steel water pipe is quite useful for the arm and you can buy brass screw clamp fittings quite easily, to fit. Don't use a knife blade or a point suspension. Ball on a flat, crossed cylinder, crossed wire and crossed foil suspensions are all OK. Single wire and single foil (Cardan hinge) may also be OK. See _http://pages.prodigy.net/fxc/_ (http://pages.prodigy.net/fxc/) _http://pages.prodigy.net/fxc/JC.html_ (http://pages.prodigy.net/fxc/JC.html) _http://www.jclahr.com/science/psn/gldn_psn.html_ (http://www.jclahr.com/science/psn/gldn_psn.html) & _http://physics.mercer.edu/petepag/MKXVII.pdf_ (http://physics.mercer.edu/petepag/MKXVII.pdf) I also have a DATAQ DI-194-RS to hook it up to a computer but no software other than what came with that unit. You won't be very happy with a 194 for very long, but it is a start. You do really need 16 bits resolution for this type of work. Remember that you also need good triggering, recording, display and data analysis software. And you do need 0.1 sec timing accuracy. Calculate how much storage space you would need at 20 sps for a single day? Eventually I want to add an optical beam sensor that will make the unit act as a tilt meter (true DC operation, similar to the differential capacitive bridge type pickup, but with much simpler support circuits) and allow experiments with feedback using the original inductive sensor as a linear motor. This should keep me busy for a year or more. You might find some information to interest you at _http://jclahr.com/science/psn/index.html_ (http://jclahr.com/science/psn/index.html) You can make OK optical sensors using large area photodiode pairs (7sq mm) and a tungsten filament lamp with either a resistance or a voltage stabilisation circuit. Infra red LEDS change their output by about a factor of 5 at constant current between 0 and 100 C, so you would need to use additional photodiode stabilisation if you used one of them. I can get down to about +/- 15 nano metres of noise, or less if I reduce the bandwidth below 10 Hz. You can also use NdFeB magnet quads and an A3515 Hall Effect sensor. See _http://www.geocities.com/meredithlamb/page003.html_ (http://www.geocities.com/meredithlamb/page003.html) Two pairs of rectangular magnets, one SN and the other NS, are mounted on parallel soft iron backing plates connected by mild steel bolts. The sensor is suspended in the central field join. There are also differential capacitor designs available - if you need sub nanometre resolution. These are a subject in themselves. Anyway, here is some "food for thought". Can I suggest that you visit _http://psn.quake.net/maillist.html#archives_ (http://psn.quake.net/maillist.html#archives) and download the last few years' letters? There is a great deal of good information and experience detailed therein. Regards, Chris Chapman
In a message dated 27/02/2005, jpopelish@........ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I am an=20 electrical engineer residing in the Shenandoah valley in central=20 Virginia.  Analog circuit design is my forte. I have been intere= sted=20 in geology, volcanism and earthquakes for a long time.  After discuss= ing=20 seismometer amplifiers with someone, recently, in sci.electronics.design,=20= I=20 started searching the web for home built seismometer and sensor designs.&n= bsp;=20

One thing that struck me about many of the sensor designs is their= =20 lack of optimisation and sophistication.  Either this means that the=20 sensor is not the limiting part of most designs or else it means that=20 considerable improvement is possible.
Hi John,
 
    Welcome! I can't comment on your discussions -=20= I=20 can't find the website you quote. Seismometer amplifiers do need quite=20 specialised design with low noise, low drift, high gain and good filters wit= h a=20 low pulse overshoot.  
 
    I don't know where you are finding the 'many'=20 amplifier designs? There is one on Larry's website which uses LT1007s and is= =20 optimised. You need to optimise both current and voltage noise sources. LT10= 07s,=20 OP07s and OP27s can all give satisfactory performance. If you wish to u= se=20 very long periods where 1/f noise is a limitation, MAX432 and chopper amp=20 circuits are available. Don't confuse apparently simple with unsophisticated= !=20 You are trying to get the amplifier noise a factor of 10 lower than the seis= mic=20 noise. The ready availability of inexpensive but powerful NdFeB magnets= has=20 allowed the use of smaller sensor coils and magnets with increased=20 sensitivity. 
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>After=20 puzzling a bit over how I might design an inductive sensor that would impr= ove=20 upon the simple solenoidal coil and horse shoe magnet approach, I think I=20= have=20 come up with a more sensitive design that also has noise cancelling capabi= lity=20 that will help it reject line generated fields (AC hum), variations in the= =20 Earth's magnetic field caused by the solar wind and lightning magnetic fie= lds.=20 This is based on making two similar coils that produce equal and opposite=20 signals when exposed to large, common, external fields, but produce equal=20= and=20 aiding signals when exposed to the relative movement between the coils and= =20 magnet structure.  The magnet structure also has no net external fiel= d to=20 interact with the geo field that might interact with the seismometer=20 boom.

I have purchased a batch of NeFeB magnets on EBAY and am awai= ting=20 a quote for construction of the 6 iron pole pieces to make one of these fi= st=20 sized sensors.  I will make the coil forms and wind the coils,=20 myself.  I will also make the signal amplifier and filter.  If t= hat=20 all comes together, I will take a shot at building a Lehman=20 type
horizontal, long period pendulum. 
    I suggest that you consider 1" square NdFe= B=20 magnets in a quad formation, NS opposing SN, in between two 1/4" thick=20 rectangular mild steel plates, say 3.5" long by 2" wide. You wind a flat=20 rectangular coil to half cover the magnet poles, say ~1" square. The coil is= =20 completely screened by the soft iron backing plates, which should be earthed= to=20 the same point as the seismometer frame and the amplifier inputs. You can us= e=20 the same layout, but with thicker rectangular 1" x 1/2" magnets for an=20= Al=20 or Cu inductive damping plate. This design gives very low stray external=20 magnetic fields. Try it - you will like it!
    AC hum is fairly low and is strongly filtered b= y=20 your 3 to 10 Hz amplifier filters. You should use woven screen=20 connecting cable. The main problem in domestic situations is in limiting=20 interference coming in through the utility supply and from various domestic=20 sources. Fridges, cookers and electrical heating systems can produ= ce=20 large surges. You may benefit from a line filter. It is preferable to make t= he=20 seismometer arm and weight using non magnetic materials. Stainless steel wat= er=20 pipe is quite useful for the arm and you can buy brass screw clamp fittings=20 quite easily, to fit.
 <= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I also=20 have a DATAQ DI-194-RS to hook it up to a computer but no software other t= han=20 what came with that unit.
    You won't be very happy with a 194 for very lon= g,=20 but it is a start. You do really need 16 bits resolution for this type of wo= rk.=20 Remember that you also need good triggering, recording, display and data=20 analysis software. And you do need 0.1 sec timing accuracy. Calculate how mu= ch=20 storage space you would need at 20 sps for a single day?
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Eventually I want to add an optical beam sensor that will make th= e unit=20 act as a tilt meter (true DC operation, similar to the differential capaci= tive=20 bridge type pickup, but with much simpler support circuits) and allow=20 experiments with feedback using the
original inductive sensor as a line= ar=20 motor.  This should keep me busy for a year or more.
    You might find some information to interest you= at=20 http://jclahr.com/science/= psn/index.html You=20 can make OK optical sensors using large area photodiode pairs (7sq mm) and a= =20 tungsten filament lamp with either a resistance or a voltage stabilisat= ion=20 circuit. Infra red LEDS change their output by about a factor of 5 at consta= nt=20 current between 0 and 100 C, so you would need to use additional photod= iode=20 stabilisation if you used one of them. I can get down to about +/- 15 nano=20 metres of noise, or less if I reduce the bandwidth below 10 Hz.
 
    You can also use NdFeB magnet quads and an A351= 5=20 Hall Effect sensor. See http://www.geoci= ties.com/meredithlamb/page003.html Two=20 pairs of rectangular magnets, one SN and the other NS, are mounted on=20 parallel soft iron backing plates connected by mild steel bolts. The sensor=20= is=20 suspended in the central field join.
 
    There are also differential capacitor designs=20 available - if you need sub nanometre resolution. These are a subject in=20 themselves.
 
    Anyway, here is some "food for thought".
 
    Can I suggest that you visit http://psn.quake.net/ma= illist.html#archives and=20 download the last few years' letters? There is a great deal of good informat= ion=20 and experience detailed therein.
 
    Regards,
 
    Chris Chapman
Subject: Re: Switched Capacitor filters From: ChrisAtUpw@....... Date: Sun, 27 Feb 2005 23:33:50 EST =20 In a message dated 27/02/2005 13:59:22 GMT Standard Time, =20 dcrice@............ writes: Switched capacitor filters are very nice to work with, easy to design and=20 control, but they have limited dynamic range, typically less than 80 dB. No= w=20 that=E2=80=99s a lot if you=E2=80=99re just looking at an analog trace, but= only equivalent to=20 a 12 or 13 bit A/D converter. If anybody is using a 16-bit or one of the=20 24-bit delta-sigma converters, you should use digital filtering to maintain= your=20 dynamic range. Doug Crice Hi Doug, =20 Or use analogue filters? You can download a filter calculation program=20 called Filterpro from the Texas website=20 _http://focus.ti.com/analog/docs/sampleutilities.tsp?path=3Dtemplatedata/cm/= utilities/data/filterpro&templateId=3D3&family Id=3D57&navigationId=3D9742_=20 (http://focus.ti.com/analog/docs/sampleutilities.tsp?path=3Dtemplatedata/cm/= utilities/data/filterpro&templateId=3D3&familyId=3D57&navigat ionId=3D9742)=20 Switched capacitor filters should come with a wealth warning notice.... =20 Regards, =20 Chris Chapman
In a message dated 27/02/2005 13:59:22 GMT Standard Time,=20 dcrice@............ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>

Switched capacitor filters a= re=20 very nice to work with, easy to design and control, but they have limited=20 dynamic range, typically less than 80 dB. Now that=E2=80=99s a lot if you= =E2=80=99re just=20 looking at an analog trace, but only equivalent to a 12 or 13 bit A/D=20 converter. If anybody is using a 16-bit or one of the 24-bit delta-sigma=20 converters, you should use digital filtering to maintain your dynamic rang= e.=20 Doug Crice

=
Hi Doug,
 
    Or use analogue filters? You can download a fil= ter=20 calculation program called Filterpro from the Texas website http://focus.ti.com/analog/docs/sampleutilities.tsp?path= =3Dtemplatedata/cm/utilities/data/filterpro&templateId=3D3&familyId= =3D57&navigationId=3D9742
    Switched capacitor filters should come with a=20 wealth warning notice....
 
    Regards,
 
    Chris Chapman
Subject: RE: New subscriber From: John Popelish jpopelish@........ Date: Mon, 28 Feb 2005 10:35:58 -0500 ChrisAtUpw@....... wrote: > John Popelish wrote: (snip) > > One thing that struck me about many of the sensor designs is their > > lack of optimisation and sophistication. > > Either this means that the sensor is not the limiting part > > of most designs or else it means that considerable improvement > > is possible. (snip) > I don't know where you are finding the 'many' amplifier designs? There > is one on Larry's website which uses LT1007s and is optimised. You need to > optimise both current and voltage noise sources. LT1007s, OP07s and OP27s can > all give satisfactory performance. If you wish to use very long periods where > 1/f noise is a limitation, MAX432 and chopper amp circuits are available. I have my eye on the LT1007 for the front end amplifier. > Don't confuse apparently simple with unsophisticated! > You are trying to get the amplifier noise a factor of 10 lower > than the seismic noise. The ready > availability of inexpensive but powerful NdFeB magnets has allowed the use of > smaller sensor coils and magnets with increased sensitivity. I haven't addressed the amplifier design, yet. I am focused on getting the largest, cleanest possible signal out of the sensor before thinking about amplification. (snip) > > I think I have come up with a more sensitive design > > that also has noise cancelling capability (snip) > I suggest that you consider 1" square NdFeB magnets in a quad formation, > NS opposing SN, in between two 1/4" thick rectangular mild steel plates, say > 3.5" long by 2" wide. You wind a flat rectangular coil to half cover the > magnet poles, say ~1" square. I played around with this sort of approach, including using two guitar pickup coils, but even those long rectangular coils do not use all the wire to generate signal. I think I can get more output with a dual voice coil design, with one having the north pole in the center and one having the south pole in the center. I think I may be able to approach 10,000 gauss field over the entire coil, with every bit of the wire generating voltage. This will also surround the coils with the outer iron pole pieces as part of the shielding. If I figure out the file system, here, I may be able to upload a sketch of the magnet and coil structure. (snip) > AC hum is fairly low and is strongly filtered by your 3 to 10 Hz > amplifier filters. (snip) Agreed, but I hope to eliminate most of the usual noise pickup (had with the single coil sensor) with the dual coil approach. > It is preferable to make the seismometer arm and weight using > non magnetic materials. Stainless steel water pipe is quite useful > for the arm and you can buy brass screw clamp fittings quite easily, > to fit. Don't use a knife blade or a point suspension. > Ball on a flat, crossed cylinder, crossed wire and crossed foil > suspensions are all OK. Single wire and single foil (Cardan hinge) > may also be OK. See > http://pages.prodigy.net/fxc/ > http://pages.prodigy.net/fxc/JC.html > http://www.jclahr.com/science/psn/gldn_psn.html > http://physics.mercer.edu/petepag/MKXVII.pdf (snip) Thank you for these links. I haven't yet gotten very far into the design of the pendulum system. What do you dislike about the knife edge hinges? (re: optical beam sensors) > You might find some information to interest you at > http://jclahr.com/science/psn/index.html > You can make OK optical sensors using large area photodiode pairs > (7sq mm) and a tungsten filament lamp with either a resistance > or a voltage stabilisation circuit. > Infra red LEDS change their output by about a factor of 5 > at constant current between 0 and 100 C, so you would need > to use additional photodiode stabilisation if you used one of them. > I can get down to about +/- 15 nano metres of > noise, or less if I reduce the bandwidth below 10 Hz. Thanks. I will get back to this problem, later. > You can also use NdFeB magnet quads and an A3515 Hall Effect sensor. > See > http://www.geocities.com/meredithlamb/page003.html > Two pairs of rectangular magnets, one SN > and the other NS, are mounted on parallel soft iron backing plates > connected by mild steel bolts. The sensor is suspended in the > central field join. I haven't considered Hall effect devices. Do you have any idea how stable and clean these are, compared to the optical approach, you describe, above? > There are also differential capacitor designs available > - if you need sub nanometre resolution. These are a subject > in themselves. > > Anyway, here is some "food for thought". > > Can I suggest that you visit > http://psn.quake.net/maillist.html#archives > and download the last few years' letters? > There is a great deal of good information and experience > detailed therein. I have been wading in, hip deep the last few days, but with many people posting in multi part mime and html, the signal to noise ration is pretty low. Thank you for your advice. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: AmaSeis, thanks From: Stephen & Kathy skmort@.......... Date: Mon, 28 Feb 2005 09:12:40 -0800 WOW,, Many thanks to all who have responded to my question about AmaSeis and DataQ 150RS,, the info and suggestions are very helpful and will keep me busy for weeks!!!!! I will also try emailing Alan again,, I'm very hopeful that I will get it to work,, it will hold my interest until I get Larry's board in the next year, or two!!! Thanks again,, Stephen PSN Station #55 near Pilot Hill Ca. USA 38.828N 120.979W __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: New subscriber From: "Steve Hammond" shammon1@............. Date: Mon, 28 Feb 2005 11:05:13 -0800 Hi John, Hi Chris and others, You can find what many consider to be the original PSN amp design at http://pw2.netcom.com/~shammon1/equip.htm#Plans in the right column. In my document files, I also have an older design done by Jan Froom which dates back before 1989 which includes a 12-bit A/D. Pete Row designed the amp and filter found on the website and freely gave it to the members of the PSN group in 1990 at one of the first PSN meetings we held. That was at a time when the group was less than 20 members. Pete does analog design as a profession and spent an hour describing the circuit operation in detail. I'm not a designer so I wont even attempt to go there... Below that, on the same web page, you will find another design which came from Sean Morrissey. Sean has passed as may know and was also a world class designer. I have been using Pete's design for 15 years and it is easy to build and diagnose when an op-amp fails. I currently have five amp/filter sets connected to Larry's serial A/D board. You can find example seismic data on Larry's site under the ATx prefix from Aptos, CA. The ATZ, ATN and ATE are HS-10 geophones and the data from AT1 and AT2 are from Lehman's. Regards, Steve Hammond PSN San Jose Aptos, CA www.publicseismicnetwork.com -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of ChrisAtUpw@....... Sent: Sunday, February 27, 2005 7:53 PM To: psn-l@.............. Subject: Re: New subscriber In a message dated 27/02/2005, jpopelish@........ writes: I am an electrical engineer residing in the Shenandoah valley in central Virginia. Analog circuit design is my forte. I have been interested in geology, volcanism and earthquakes for a long time. After discussing seismometer amplifiers with someone, recently, in sci.electronics.design, I started searching the web for home built seismometer and sensor designs. One thing that struck me about many of the sensor designs is their lack of optimisation and sophistication. Either this means that the sensor is not the limiting part of most designs or else it means that considerable improvement is possible. Hi John, Welcome! I can't comment on your discussions - I can't find the website you quote. Seismometer amplifiers do need quite specialised design with low noise, low drift, high gain and good filters with a low pulse overshoot. I don't know where you are finding the 'many' amplifier designs? There is one on Larry's website which uses LT1007s and is optimised. You need to optimise both current and voltage noise sources. LT1007s, OP07s and OP27s can all give satisfactory performance. If you wish to use very long periods where 1/f noise is a limitation, MAX432 and chopper amp circuits are available. Don't confuse apparently simple with unsophisticated! You are trying to get the amplifier noise a factor of 10 lower than the seismic noise. The ready availability of inexpensive but powerful NdFeB magnets has allowed the use of smaller sensor coils and magnets with increased sensitivity. After puzzling a bit over how I might design an inductive sensor that would improve upon the simple solenoidal coil and horse shoe magnet approach, I think I have come up with a more sensitive design that also has noise cancelling capability that will help it reject line generated fields (AC hum), variations in the Earth's magnetic field caused by the solar wind and lightning magnetic fields. This is based on making two similar coils that produce equal and opposite signals when exposed to large, common, external fields, but produce equal and aiding signals when exposed to the relative movement between the coils and magnet structure. The magnet structure also has no net external field to interact with the geo field that might interact with the seismometer boom. I have purchased a batch of NeFeB magnets on EBAY and am awaiting a quote for construction of the 6 iron pole pieces to make one of these fist sized sensors. I will make the coil forms and wind the coils, myself. I will also make the signal amplifier and filter. If that all comes together, I will take a shot at building a Lehman type horizontal, long period pendulum. I suggest that you consider 1" square NdFeB magnets in a quad formation, NS opposing SN, in between two 1/4" thick rectangular mild steel plates, say 3.5" long by 2" wide. You wind a flat rectangular coil to half cover the magnet poles, say ~1" square. The coil is completely screened by the soft iron backing plates, which should be earthed to the same point as the seismometer frame and the amplifier inputs. You can use the same layout, but with thicker rectangular 1" x 1/2" magnets for an Al or Cu inductive damping plate. This design gives very low stray external magnetic fields. Try it - you will like it! AC hum is fairly low and is strongly filtered by your 3 to 10 Hz amplifier filters. You should use woven screen connecting cable. The main problem in domestic situations is in limiting interference coming in through the utility supply and from various domestic sources. Fridges, cookers and electrical heating systems can produce large surges. You may benefit from a line filter. It is preferable to make the seismometer arm and weight using non magnetic materials. Stainless steel water pipe is quite useful for the arm and you can buy brass screw clamp fittings quite easily, to fit. Don't use a knife blade or a point suspension. Ball on a flat, crossed cylinder, crossed wire and crossed foil suspensions are all OK. Single wire and single foil (Cardan hinge) may also be OK. See http://pages.prodigy.net/fxc/ http://pages.prodigy.net/fxc/JC.html http://www.jclahr.com/science/psn/gldn_psn.html & http://physics.mercer.edu/petepag/MKXVII.pdf I also have a DATAQ DI-194-RS to hook it up to a computer but no software other than what came with that unit. You won't be very happy with a 194 for very long, but it is a start. You do really need 16 bits resolution for this type of work. Remember that you also need good triggering, recording, display and data analysis software. And you do need 0.1 sec timing accuracy. Calculate how much storage space you would need at 20 sps for a single day? Eventually I want to add an optical beam sensor that will make the unit act as a tilt meter (true DC operation, similar to the differential capacitive bridge type pickup, but with much simpler support circuits) and allow experiments with feedback using the original inductive sensor as a linear motor. This should keep me busy for a year or more. You might find some information to interest you at http://jclahr.com/science/psn/index.html You can make OK optical sensors using large area photodiode pairs (7sq mm) and a tungsten filament lamp with either a resistance or a voltage stabilisation circuit. Infra red LEDS change their output by about a factor of 5 at constant current between 0 and 100 C, so you would need to use additional photodiode stabilisation if you used one of them. I can get down to about +/- 15 nano metres of noise, or less if I reduce the bandwidth below 10 Hz. You can also use NdFeB magnet quads and an A3515 Hall Effect sensor. See http://www.geocities.com/meredithlamb/page003.html Two pairs of rectangular magnets, one SN and the other NS, are mounted on parallel soft iron backing plates connected by mild steel bolts. The sensor is suspended in the central field join. There are also differential capacitor designs available - if you need sub nanometre resolution. These are a subject in themselves. Anyway, here is some "food for thought". Can I suggest that you visit http://psn.quake.net/maillist.html#archives and download the last few years' letters? There is a great deal of good information and experience detailed therein. Regards, Chris Chapman
Hi John, Hi Chris and = others,
You can find what many consider to = be the=20 original PSN amp design at http://pw2.netco= m.com/~shammon1/equip.htm#Plans in=20 the right column. In my document files,  I also have an older = design done=20 by Jan Froom which dates back before 1989 which includes a 12-bit = A/D. Pete=20 Row designed the amp and filter found on the website and freely gave it = to the=20 members of the PSN group in 1990 at one of the first PSN meetings we = held. That=20 was at a time when the group was less than 20 members. Pete does analog=20 design as a profession and spent an hour describing the circuit = operation=20 in detail. I'm not a designer so I wont even attempt to go there... = Below that,=20 on the same web page, you will find another design which came from = Sean=20 Morrissey. Sean has passed as may know and was also a world = class=20 designer. I have been using Pete's design for 15 years and it is easy to = build=20 and diagnose when an op-amp fails. I currently have five amp/filter sets = connected to Larry's serial A/D board. You can find example seismic data = on=20 Larry's site under the ATx prefix from Aptos, CA. The ATZ, ATN and ATE = are HS-10=20 geophones and the data from AT1 and AT2 are from Lehman's.
 
Regards, Steve Hammond PSN San=20 Jose
    Aptos, CA=20
www.publicseismicnetwork.com=
 
 
-----Original Message-----
From:=20 psn-l-request@.............. = [mailto:psn-l-request@...............On Behalf=20 Of ChrisAtUpw@.......
Sent: Sunday, February 27, 2005 = 7:53=20 PM
To: psn-l@..............
Subject: Re: New=20 subscriber

In a message dated 27/02/2005, jpopelish@........ writes:
I am an = electrical engineer=20 residing in the Shenandoah valley in central Virginia.  Analog = circuit=20 design is my forte. I have been interested in geology, = volcanism and=20 earthquakes for a long time.  After discussing seismometer = amplifiers=20 with someone, recently, in sci.electronics.design, I started = searching the=20 web for home built seismometer and sensor designs. 

One = thing=20 that struck me about many of the sensor designs is their lack of=20 optimisation and sophistication.  Either this means that the = sensor is=20 not the limiting part of most designs or else it means that = considerable=20 improvement is possible.
Hi John,
 
    Welcome! I can't comment on your = discussions - I=20 can't find the website you quote. Seismometer amplifiers do need quite = specialised design with low noise, low drift, high gain and good = filters with=20 a low pulse overshoot.  
 
    I don't know where you are finding the = 'many'=20 amplifier designs? There is one on Larry's website which uses LT1007s = and is=20 optimised. You need to optimise both current and voltage noise = sources.=20 LT1007s, OP07s and OP27s can all give satisfactory = performance. If you=20 wish to use very long periods where 1/f noise is a limitation, MAX432 = and=20 chopper amp circuits are available. Don't confuse apparently simple = with=20 unsophisticated! You are trying to get the amplifier noise a factor of = 10=20 lower than the seismic noise. The ready availability of inexpensive = but=20 powerful NdFeB magnets has allowed the use of smaller sensor = coils and=20 magnets with increased sensitivity. 
After puzzling = a bit over=20 how I might design an inductive sensor that would improve upon the = simple=20 solenoidal coil and horse shoe magnet approach, I think I have come = up with=20 a more sensitive design that also has noise cancelling capability = that will=20 help it reject line generated fields (AC hum), variations in the = Earth's=20 magnetic field caused by the solar wind and lightning magnetic = fields. This=20 is based on making two similar coils that produce equal and opposite = signals=20 when exposed to large, common, external fields, but produce equal = and aiding=20 signals when exposed to the relative movement between the coils and = magnet=20 structure.  The magnet structure also has no net external field = to=20 interact with the geo field that might interact with the seismometer = boom.

I have purchased a batch of NeFeB magnets on EBAY and = am=20 awaiting a quote for construction of the 6 iron pole pieces to make = one of=20 these fist sized sensors.  I will make the coil forms and wind = the=20 coils, myself.  I will also make the signal amplifier and = filter. =20 If that all comes together, I will take a shot at building a Lehman=20 type
horizontal, long period pendulum. 
    I suggest that you consider 1" = square NdFeB=20 magnets in a quad formation, NS opposing SN, in between two 1/4" = thick=20 rectangular mild steel plates, say 3.5" long by 2" wide. You wind a = flat=20 rectangular coil to half cover the magnet poles, say ~1" square. The = coil is=20 completely screened by the soft iron backing plates, which should be = earthed=20 to the same point as the seismometer frame and the amplifier inputs. = You can=20 use the same layout, but with thicker rectangular 1" x 1/2" = magnets for=20 an Al or Cu inductive damping plate. This design gives very low stray = external=20 magnetic fields. Try it - you will like it!
    AC hum is fairly low and is strongly = filtered by=20 your 3 to 10 Hz amplifier filters. You should use woven = screen=20 connecting cable. The main problem in domestic situations is in = limiting=20 interference coming in through the utility supply and from various = domestic=20 sources. Fridges, cookers and electrical heating systems can = produce=20 large surges. You may benefit from a line filter. It is preferable to = make the=20 seismometer arm and weight using non magnetic materials. Stainless = steel water=20 pipe is quite useful for the arm and you can buy brass screw clamp = fittings=20 quite easily, to fit.
    Don't use a knife blade or a point=20 suspension. Ball on a flat, crossed cylinder, crossed wire and crossed = foil=20 suspensions are all OK. Single wire and single foil (Cardan hinge) may = also be=20 OK. See http://pages.prodigy.net/fxc/&= nbsp;   http://pages.prodigy.net/fx= c/JC.html =20 http://www.jclah= r.com/science/psn/gldn_psn.html &=20 http://physics.merc= er.edu/petepag/MKXVII.pdf
I also have a=20 DATAQ DI-194-RS to hook it up to a computer but no software other = than what=20 came with that unit.
    You won't be very happy with a 194 for = very long,=20 but it is a start. You do really need 16 bits resolution for this type = of=20 work. Remember that you also need good triggering, recording, display = and data=20 analysis software. And you do need 0.1 sec timing accuracy. Calculate = how much=20 storage space you would need at 20 sps for a single day?
Eventually I=20 want to add an optical beam sensor that will make the unit act as a = tilt=20 meter (true DC operation, similar to the differential capacitive = bridge type=20 pickup, but with much simpler support circuits) and allow = experiments with=20 feedback using the
original inductive sensor as a linear = motor. =20 This should keep me busy for a year or more.
    You might find some information to = interest you=20 at http://jclahr.com/scien= ce/psn/index.html You=20 can make OK optical sensors using large area photodiode pairs (7sq mm) = and a=20 tungsten filament lamp with either a resistance or a voltage=20 stabilisation circuit. Infra red LEDS change their output by about a = factor of=20 5 at constant current between 0 and 100 C, so you would need to = use=20 additional photodiode stabilisation if you used one of them. I can get = down to=20 about +/- 15 nano metres of noise, or less if I reduce the bandwidth = below 10=20 Hz.
 
    You can also use NdFeB magnet quads and = an A3515=20 Hall Effect sensor. See http://www.ge= ocities.com/meredithlamb/page003.html Two=20 pairs of rectangular magnets, one SN and the other NS, are = mounted on=20 parallel soft iron backing plates connected by mild steel bolts. The = sensor is=20 suspended in the central field join.
 
    There are also differential capacitor = designs=20 available - if you need sub nanometre resolution. These are a subject = in=20 themselves.
 
    Anyway, here is some "food for thought". =
 
    Can I suggest that you visit http://psn.quake.net= /maillist.html#archives and=20 download the last few years' letters? There is a great deal of good=20 information and experience detailed therein.
 
    Regards,
 
    Chris=20 Chapman
Subject: RE: New subscriber From: John Popelish jpopelish@........ Date: Tue, 01 Mar 2005 04:42:09 -0500 "Steve Hammond" wrote: > Hi John, Hi Chris and others, > You can find what many consider to be the original PSN amp design > at http://pw2.netcom.com/~shammon1/equip.htm#Plans in the right column. > In my document files, I also have an older design done by Jan Froom > which dates back before 1989 which includes a 12-bit A/D. > Pete Row designed the amp and filter found on the website > and freely gave it to the members of the PSN group in 1990 > at one of the first PSN meetings we held. (snip) > Below that, on the same web page, you will find another design > which came from Sean Morrissey. Sean has passed as may know > and was also a world class designer. I have been using Pete's design > for 15 years and it is easy to build and diagnose when an op-amp fails. (snip) Thank you, Steve, for this information. I will review these amplifier and filter designs, in detail, including all filter responses. Are you interested in seeing my critique of these when I get to that? I am sure my design will steal from them, though I think I might be able to slightly improve upon some aspects, based on a quick look. I will make available to the group anything that I design, including a parts list, theory of operation, and schematic. If you have any other schematics in emailable form that you would like me to consider, you may email them to me at jpopelish@......... I am not worried about this address appearing in public, since it is what I have used on usenet for a few years. I often tutor, there, on sci.electronics.basics. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Seismic detector circuit schematics From: John or Jan Lahr JohnJan@........ Date: Tue, 01 Mar 2005 07:56:14 -0700 Hi John,

I've posted some schematics on my web site as well.

Amplifier/Filter circuit from Chris Chapman:
http://jclahr.com/science/psn/amp_filt/

Linear Variable Differential Transformer sensor from Chris Chapman:
http://jclahr.com/science/psn/chapman/lvdt/lvdt1.html
 http://jclahr.com/science/psn/chapman/lvdt/lvdt2.html

Folded pendulum seismometer electronics package from David H. Youden:
http://jclahr.com/science/psn/youden/electronics/fpelectronics.html

Basic optical sensor circuit for a self-centering SG type pendulum system
from Chris Chapman:
http://jclahr.com/science/psn/chapman/photo_detect/

Micorphone amplifier for use with gunshot location system using
a TLE2426ILP to avoid need for dual power supply from Fred Fischer :
http://jclahr.com/science/psn/gunshots/of93221/fig1.gif

Is the use of a 1/2 rail virtual ground a good idea for seismic
amplifiers?  What is a newer part for this purpose?  See:
< http://www.digikey.com/scripts/dksearch/dksus.dll?KeywordSearch?Mpart=TLE2426ILP&site=us >

Symmetric differential capacitive sensor from Randall Peters:
http://jclahr.com/science/psn/capacitive/

Folded pendulum design from Brady Romberg's team at the
Colorado School of Mines:
http://jclahr.com/science/psn/epics/reports/folded/

Cheers,
John Lahr


At 02:42 AM 3/1/2005, you wrote:
"Steve Hammond" <shammon1@.............> wrote:

> Hi John, Hi Chris and others,
> You can find what many consider to be the original PSN amp design
> at http://pw2.netcom.com/~shammon1/equip.htm#Plans in the right column.
> In my document files,  I also have an older design done by Jan Froom
> which dates back before 1989 which includes a 12-bit A/D.
> Pete Row designed the amp and filter found on the website
> and freely gave it to the members of the PSN group in 1990
> at one of the first PSN meetings we held.
(snip)
> Below that, on the same web page, you will find another design
> which came from Sean Morrissey. Sean has passed as may know
> and was also a world class designer. I have been using Pete's design
> for 15 years and it is easy to build and diagnose when an op-amp fails.
(snip)

Thank you, Steve, for this information. 
I will review these amplifier and filter designs, in detail,
including all filter responses.

Are you interested in seeing my critique of these when I get to that?

I am sure my design will steal
from them, though I think I might be able to slightly improve
upon some aspects, based on a quick look. 
I will make available to the group anything that I design,
including a parts list, theory of operation, and schematic. 

If you have any other schematics in emailable form that you would
like me to consider, you may email them to me at jpopelish@.........
I am not worried about this address appearing in public,
since it is what I have used on usenet for a few years.
I often tutor, there, on sci.electronics.basics.

--
John Popelish
__________________________________________________________

Public Seismic Network Mailing List (PSN-L)

http://www.seismicnet.com/maillist.html for more information.


##################################/ John C. Lahr
#################################/ Emeritus Seismologist
################################/ U.S. Geological Survey
===========================/ Geologic Hazards Team, MS966
##############################/ PO Box 25046
#############################//##############################
############################//###############################
     Denver, Colorado 80225-0046 /################################
             Phone: (303) 215-9913 /=============================
               Fax: (303) 273-8540 /##################################
                     lahr@........ /###################################
                                          /####################################
                                 http://jclahr.com/science/
 Subject: RE: New subscriber From: "Steve Hammond" shammon1@............. Date: Tue, 1 Mar 2005 09:19:21 -0800 Sure John. We can also post your additional design to the site along with the others if you want to do this. Send the design directly to me with PSN: in the start of the subject line so I don't trash it in the spam mail whenever you finish it. Regards, Steve -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of John Popelish Sent: Tuesday, March 01, 2005 1:42 AM To: PSN-L@.............. Subject: RE: New subscriber "Steve Hammond" wrote: > Hi John, Hi Chris and others, > You can find what many consider to be the original PSN amp design > at http://pw2.netcom.com/~shammon1/equip.htm#Plans in the right column. > In my document files, I also have an older design done by Jan Froom > which dates back before 1989 which includes a 12-bit A/D. > Pete Row designed the amp and filter found on the website > and freely gave it to the members of the PSN group in 1990 > at one of the first PSN meetings we held. (snip) > Below that, on the same web page, you will find another design > which came from Sean Morrissey. Sean has passed as may know > and was also a world class designer. I have been using Pete's design > for 15 years and it is easy to build and diagnose when an op-amp fails. (snip) Thank you, Steve, for this information. I will review these amplifier and filter designs, in detail, including all filter responses. Are you interested in seeing my critique of these when I get to that? I am sure my design will steal from them, though I think I might be able to slightly improve upon some aspects, based on a quick look. I will make available to the group anything that I design, including a parts list, theory of operation, and schematic. If you have any other schematics in emailable form that you would like me to consider, you may email them to me at jpopelish@......... I am not worried about this address appearing in public, since it is what I have used on usenet for a few years. I often tutor, there, on sci.electronics.basics. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismic detector circuit schematics From: John Popelish jpopelish@........ Date: Tue, 01 Mar 2005 18:42:07 -0500 > John Lahr wrote: (I have edited your post to plain test to make it read easier in the archive, since it contains so much useful information. Hope that is okay.) > Hi John, > I've posted some schematics on my web site as well. > > Amplifier/Filter circuit from Chris Chapman: > http://jclahr.com/science/psn/amp_filt/ > > Linear Variable Differential Transformer sensor from Chris Chapman: > http://jclahr.com/science/psn/chapman/lvdt/lvdt1.html > http://jclahr.com/science/psn/chapman/lvdt/lvdt2.html > > Folded pendulum seismometer electronics package from David H. Youden: > http://jclahr.com/science/psn/youden/electronics/fpelectronics.html > > Basic optical sensor circuit for a self-centering > SG type pendulum from Chris Chapman: > http://jclahr.com/science/psn/chapman/photo_detect/ > > Micorphone amplifier for use with gunshot location system using > a TLE2426ILP to avoid need for dual power supply from Fred Fischer: > http://jclahr.com/science/psn/gunshots/of93221/fig1.gif > > Is the use of a 1/2 rail virtual ground a good idea for seismic > amplifiers? I don't see why not. > What is a newer part for this purpose? (snip Digikey search) That is the only single part rail splitter I have seen, but any rail-to-rail or single supply opamp that tolerates a fair amount of capacitance on its output will do this job with a two resistor divider across the rails fed into a follower configuration. An opamp that don't tolerate capacitance so well needs an additional low value resistor between the opamp output and the derived ground rail to make sure it is stable, since there will be bypass caps between the positive and negative rails and this derived ground, scattered around the board. No special part needed, unless you are going for the absolute minimum number of components. You just have to add up the worst case total ground current and make sure the opamp is capable of supplying that without current limiting. > Symmetric differential capacitive sensor from Randall Peters: > http://jclahr.com/science/psn/capacitive/ > > Folded pendulum design from Brady Romberg's team at the > Colorado School of Mines: > http://jclahr.com/science/psn/epics/reports/folded/ > > Cheers, > John Lahr Thanks for this library of links. I have something to study for the next few days. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: AmaSeis & DataQ 150RS From: Stephen & Kathy skmort@.......... Date: Tue, 01 Mar 2005 20:25:34 -0800 FYI,, Good news,,, the most often stated advice from the PSN was to get the latest Update for AmaSeis,, which was the first thing I did!! I was very surprised to see that there had been 4 or 5 updates since I downloaded the program last October,,,,, the bottom line, I've been recording for about 24 hours now and everything seems to be working just fine!!! I'm using the DataQ 151 option,,, haven't tried any of the other options yet,,, had to set up the ini file as per instructions in the help file for the DataQ, which I had already done last Oct.!! It didn't require me to set the DataQ to single channel,, which makes it convienent if I want to go back to the DataQ software!! It even went through an automatic 12 sec. time adjust at 11:00 UTC (03:00 local) without a hitch,,, (my computer gains about 12 sec per day) I probably lost 12 sec. of data, but I can live with that!! Now all we need is a quake,,, not too big of course,, ha!!! Many thanks again for all the help, Stephen PSN Station #55 near Pilot Hill Ca. USA 38.828N 120.979W __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: posting From: "RANDY KIMBALL" randy.kimball@........... Date: Sun, 06 Mar 2005 17:28:55 -0600 I have a few event files I would like to post to the quake data files. I guess I need to learn what to do first and then how to post/to what = location from my WinQuake data. Could someone be kind enough to lead me through that process? I have three sensors: Two Lehmans I built with Frank Coopers and John Cole's e-mail = assistance. Using John's wonderful big wire wound coils. They are of aluminum construction with Neonib magnets, oil = dampened. The third is a Z axis prototype I am messing with, using magnet = repulsion in a horizontal beam with a pivot at one end. All sensors are run through Larry's A/D and Amp boards to WinSDR. I've been away to New Zealand and just returned, There are a few files = I'd like to post. -randy- in Keller, Texas 32.93N - 97.23W

I have a few event files I would like = to post to=20 the quake data files.
 
I guess I need to learn what to do = first and then=20 how to post/to what location from my WinQuake data.
 
Could someone be kind enough to lead me = through=20 that process?
 
I have three sensors:
    Two Lehmans I built = with Frank=20 Coopers and John Cole's e-mail assistance.   Using John's = wonderful=20 big wire wound coils.
        = They are of=20 aluminum construction with Neonib magnets, oil dampened.
 
    The third is a Z = axis prototype=20 I am messing with, using magnet repulsion in a horizontal beam with a = pivot at=20 one end.
 
All sensors are run through Larry's A/D = and Amp=20 boards to WinSDR.
 
I've been away to New Zealand and just = returned,=20 There are a few files I'd like to post.
 
-randy- in Keller, Texas  32.93N - = 97.23W
 
 
Subject: From: "Dewayne Hill" n0ssy@........... Date: Sun, 6 Mar 2005 19:51:05 -0700 I am thinking of building an AS-1 type seismometer. Can anyone tell me what type of spring I should use and where it can be = obtained from? Dewayne Hill=20 Westminster, Co.
I am thinking of building an AS-1 type=20 seismometer.
 
Can anyone tell me what type of spring = I should use=20 and where it can be obtained from?
 
 
Dewayne Hill
Westminster,=20 Co.
Subject: Re: From: "RANDY KIMBALL" randy.kimball@........... Date: Sun, 06 Mar 2005 21:13:43 -0600 I think John cole can help with that info... I bet he is listening in. = he wound his own spring. -randy- ----- Original Message -----=20 From: Dewayne Hill=20 To: psn-l@................. Sent: Sunday, March 06, 2005 8:51 PM I am thinking of building an AS-1 type seismometer. Can anyone tell me what type of spring I should use and where it can = be obtained from? Dewayne Hill=20 Westminster, Co.
I think John cole can help with that = info... I bet=20 he is listening in.  he wound his own spring.
 
-randy-
----- Original Message -----
From:=20 Dewayne = Hill=20
Sent: Sunday, March 06, 2005 = 8:51=20 PM

I am thinking of building an AS-1 = type=20 seismometer.
 
Can anyone tell me what type of = spring I should=20 use and where it can be obtained from?
 
 
Dewayne Hill
Westminster,=20 Co.
Subject: Re: posting From: Larry Cochrane lcochrane@.............. Date: Sun, 06 Mar 2005 22:59:50 -0800 Randy, First you need a unique station / sensor ID for event files. This is the file name extension just before the .psn. I checked and *.rk*.psn has not been used, so you could use *.rk1, *.rk2 etc for your sensor IDs. To archive them on my system send the event files as attachments to event@............... You can also setup WinQuake to send in your files. See http://www.seismicnet.com/wqdocs/dlghelp.html#Send%20EMail for more information. Larry Cochrane Redwood City, PSN RANDY KIMBALL wrote: > I have a few event files I would like to post to the quake data files. > > I guess I need to learn what to do first and then how to post/to what location from my WinQuake data. > > Could someone be kind enough to lead me through that process? > > I have three sensors: > Two Lehmans I built with Frank Coopers and John Cole's e-mail assistance. Using John's wonderful big wire wound coils. > They are of aluminum construction with Neonib magnets, oil dampened. > > The third is a Z axis prototype I am messing with, using magnet repulsion in a horizontal beam with a pivot at one end. > > All sensors are run through Larry's A/D and Amp boards to WinSDR. > > I've been away to New Zealand and just returned, There are a few files I'd like to post. > > -randy- in Keller, Texas 32.93N - 97.23W > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Op amp front end noise From: John Popelish jpopelish@........ Date: Wed, 09 Mar 2005 20:57:24 -0500 I am getting pretty deeply into the design process for a velocity coil seismometer amplifier and filter and have decided to try ot quantify the relative noise performance of various candidate opamps versus coil resistance. Here is the list of low noise and general purpose types (which I have on hand) that I am comparing: AD706 AD708 AD820 AD822 ICL6750S LF411 LMC6062 LMC6462 LMC6482 LT1007 LI1115 LT1124 LT1128 LT1677 LT1047 LTC1051 LTC1151 MAX400 MAX410 MAX420 MAX427 MAX430 MCP6022 OP07 OP177 OP2604 OP27 OP97 Do you have any suggestions for other candidates I might evaluate? My biggest difficulty in completing this task has been resolving the wide variation in noise specifications for the various types to produce a valid comparison in the DC to 10 Hz frequency range, especially comparing the chopper types to the others. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: ChrisAtUpw@....... Date: Wed, 9 Mar 2005 23:35:44 EST In a message dated 10/03/2005, jpopelish@........ writes: I am getting pretty deeply into the design process for a velocity coil seismometer amplifier and filter and have decided to try to quantify the relative noise performance of various candidate opamps versus coil resistance. Here is the list of low noise and general purpose types (which I have on hand) that I am comparing: LT1007 OP27 OP07 ` Good luck! OPA604? LT1028 LT1677 Linear have noise tables for opamps. These are the commonly used ones for coil / magnet systems. The choice very much depends on the source resistance that you need to match. Coil systems do not normally sense down to DC, but to some maximum period. You put in a high pass filter to remove the 1/f noise and any drift. The 1/f noise can be very significant. The MAX432 has about the best specifications of the CAZ group. These are useful if you want very long periods, since they do not have any 1/f noise, but they are essentially best for high impedance inputs. They work quite well for DC systems, since they have very low thermal drift. You can get very significantly improved noise performance using discrete transistor inputs, either fet, npn or pnp and also by using a true chopper amplifier. My biggest difficulty in completing this task has been resolving the wide variation in noise specifications for the various types to produce a valid comparison in the DC to 10 Hz frequency range, especially comparing the chopper types to the others. The chopper types quoted seem to be all fet input, which have high impedance inputs. The current noise is very low, but the voltage noise is significant. There is a paper from the 90's? comparing noise in seismometer amplifier systems, but it is now a bit out of date. I can't remember the reference off hand - I think it was bull seis soc am. I am away from home at the moment, so I can't look it up. I am sure that this sort of choice has been described in psn.quake.net Archives - try putting in a query? Sean Morrissey? Regards, Chris Chapman
In a message dated 10/03/2005, jpopelish@........ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I am=20 getting pretty deeply into the design process for a velocity coil seismome= ter=20 amplifier and filter and have decided to try to quantify the relative nois= e=20 performance of various candidate opamps versus coil resistance.  Here= is=20 the list of low noise and general purpose types (which I have on hand) tha= t I=20 am comparing:

LT1007
OP27
OP07
`    Good luck!
 
    OPA604?
    LT1028
    LT1677
    Linear have noise tables for opamps.
 
    These are the commonly used ones for coil / mag= net=20 systems. The choice very much depends on the source=20 resistance that you need to match.
    Coil systems do not normally sense down to=20 DC, but to some maximum period. You put in a high pass filter to remove=20= the=20 1/f noise and any drift. The 1/f noise can be very significant.
    The MAX432 has about the best specificat= ions=20 of the CAZ group. These are useful if you want very long periods, since they= do=20 not have any 1/f noise, but they are essentially best for high impedance=20 inputs. They work quite well for DC systems, since they have very low=20 thermal drift.
    You can get very significantly improved noise=20 performance using discrete transistor inputs, either fet, npn or= =20 pnp and also by using a true chopper amplifier.
    
   My biggest difficulty in completing this task has b= een=20 resolving the wide variation in noise specifications for the various types t= o=20 produce a valid comparison in the DC to 10 Hz frequency range, especially=20 comparing the chopper types to the others.
 
    The chopper types quoted seem to be all fet= =20 input, which have high impedance inputs. The current noise is very low,= but=20 the voltage noise is significant.
 
    There is a paper from the 90's? comparing=20 noise in seismometer amplifier systems, but it is now a bit out of= =20 date. I can't remember the reference off hand - I think it was bull sei= s=20 soc am. I am away from home at the moment, so I can't look it up. I am sure=20= that=20 this sort of choice has been described in psn.quake.net Archives - try=20 putting in a query? Sean Morrissey?
 
    Regards,
 
    Chris Chapman
Subject: Re: Op amp front end noise From: George Bush ke6pxp@....... Date: Wed, 09 Mar 2005 20:48:08 -0800 I am building a mercury-cup tiltmeter and it uses the INA121 opamp. I would be interested in seeing your analysis of it's noise also. At 08:57 PM 3/9/05 -0500, you wrote: >I am getting pretty deeply into the design process for a velocity coil >seismometer amplifier and filter and have decided to try ot quantify >the relative noise performance of various candidate opamps versus coil >resistance. Here is the list of low noise and general purpose types >(which I have on hand) that I am comparing: > >AD706 >AD708 >AD820 >AD822 >ICL6750S >LF411 >LMC6062 >LMC6462 >LMC6482 >LT1007 >LI1115 >LT1124 >LT1128 >LT1677 >LT1047 >LTC1051 >LTC1151 >MAX400 >MAX410 >MAX420 >MAX427 >MAX430 >MCP6022 >OP07 >OP177 >OP2604 >OP27 >OP97 > >Do you have any suggestions for other candidates I might evaluate? > >My biggest difficulty in completing this task has been resolving the >wide variation in noise specifications for the various types to >produce a valid comparison in the DC to 10 Hz frequency range, >especially comparing the chopper types to the others. > >-- >John Popelish >__________________________________________________________ > >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. > George __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: akr@......... Date: Wed, 9 Mar 2005 21:30:44 -0800 (PST) John and all others - I would add the quad OP-400 to the list. It is essentially a low power quad OP-07/77. It also has the added advantage of being able to drive large capacitive loads - I use it as a driver for the long cable run leading from my seismograph to the AtoD card in my computer in addition to using it for amplifying and filter applications. The data shows the OP-400 driving a 1nF load without oscillation - I took the picture when writing the OP-400 data sheet in my previous career in new product development and applications at PMI/ADI (we were bought out by ADI in 1990.) Art > I am getting pretty deeply into the design process for a velocity coil > seismometer amplifier and filter and have decided to try ot quantify > the relative noise performance of various candidate opamps versus coil > resistance. Here is the list of low noise and general purpose types > (which I have on hand) that I am comparing: > > AD706 > AD708 > AD820 > AD822 > ICL6750S > LF411 > LMC6062 > LMC6462 > LMC6482 > LT1007 > LI1115 > LT1124 > LT1128 > LT1677 > LT1047 > LTC1051 > LTC1151 > MAX400 > MAX410 > MAX420 > MAX427 > MAX430 > MCP6022 > OP07 > OP177 > OP2604 > OP27 > OP97 > > Do you have any suggestions for other candidates I might evaluate? > > My biggest difficulty in completing this task has been resolving the > wide variation in noise specifications for the various types to > produce a valid comparison in the DC to 10 Hz frequency range, > especially comparing the chopper types to the others. > > -- > John Popelish > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: Brett Nordgren Brett3kg@............. Date: Thu, 10 Mar 2005 07:51:41 -0500 John, Another factor that you may want to consider is thermal variation. At very low frequencies, below 1Hz, the effects of micro-variations in the device temperature can add additional "noise". I would imagine that in characterizing low-frequency noise, the op-amp manufacturers take pains to hold the temperature very steady, which is not what you're going to see in the real world. In real world conditions, it is possible that a device with very good temperature properties will perform better (less low frequency "noise") than one with much better noise specs, but having larger temperature coefficients. Just an aside, but related, in building very long time-constant RC filters, say 1000sec or so, if you use the lowest leakage capacitors, the largest noise source seems to be due to the variation of capacitor value with temperature and is proportional to the DC voltage on the capacitor. The capacitor charge Q=CV, and in the steady-state can be assumed to be constant. If C goes down due to a temperature change, V goes up--and the effect is fairly large. At very low frequencies, temperature effects look a lot like noise. Brett At 08:57 PM 3/9/2005 -0500, you wrote: >I am getting pretty deeply into the design process for a velocity coil >seismometer amplifier and filter and have decided to try ot quantify >the relative noise performance of various candidate opamps versus coil >resistance. Here is the list of low noise and general purpose types >(which I have on hand) that I am comparing: If my e-mail address above is not working you can always reach my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Op amp front end noise From: Jack Ivey ivey@.......... Date: Thu, 10 Mar 2005 08:32:09 -0500 I've seen this effect with thermocouple amplifiers, where moving your hand near the circuit would move the air enough to create low-frequency noise. It can be almost eliminated by pressing the circuit board between pieces of foam rubber. Jack -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Brett Nordgren Sent: Thursday, March 10, 2005 7:52 AM To: psn-l@.............. Subject: Re: Op amp front end noise John, Another factor that you may want to consider is thermal variation. At very low frequencies, below 1Hz, the effects of micro-variations in the device temperature can add additional "noise". I would imagine that in characterizing low-frequency noise, the op-amp manufacturers take pains to hold the temperature very steady, which is not what you're going to see in the real world. In real world conditions, it is possible that a device with very good temperature properties will perform better (less low frequency "noise") than one with much better noise specs, but having larger temperature coefficients. Just an aside, but related, in building very long time-constant RC filters, say 1000sec or so, if you use the lowest leakage capacitors, the largest noise source seems to be due to the variation of capacitor value with temperature and is proportional to the DC voltage on the capacitor. The capacitor charge Q=CV, and in the steady-state can be assumed to be constant. If C goes down due to a temperature change, V goes up--and the effect is fairly large. At very low frequencies, temperature effects look a lot like noise. Brett At 08:57 PM 3/9/2005 -0500, you wrote: >I am getting pretty deeply into the design process for a velocity coil >seismometer amplifier and filter and have decided to try ot quantify >the relative noise performance of various candidate opamps versus coil >resistance. Here is the list of low noise and general purpose types >(which I have on hand) that I am comparing: If my e-mail address above is not working you can always reach my mail form at: http://bnordgren.org/contactB.html using your Web browser. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Op amp front end noise From: akr@......... Date: Thu, 10 Mar 2005 08:14:36 -0800 (PST) Surrounding the amp and filter circuits with some type of material to reduce air flow is a very good idea - especially for very high gain circuits. I enclosed my entire setup with 2 inch thick panels of foam insulation. For a while I kept the chamber at a constant 70 degrees (the seismograph is located under my house which stays relatively temp stable already) but decided that the cost of eclectricity to maintain the temp was not worth it. Art > I've seen this effect with thermocouple amplifiers, where moving your hand > near the circuit would move the air enough to create low-frequency noise. > It can be almost eliminated by pressing the circuit board between pieces > of foam rubber. > > Jack > > -----Original Message----- > From: psn-l-request@.............. [mailto:psn-l-request@............... > On > Behalf Of Brett Nordgren > Sent: Thursday, March 10, 2005 7:52 AM > To: psn-l@.............. > Subject: Re: Op amp front end noise > > John, > > Another factor that you may want to consider is thermal variation. At > very > low frequencies, below 1Hz, the effects of micro-variations in the device > temperature can add additional "noise". I would imagine that in > characterizing low-frequency noise, the op-amp manufacturers take pains to > hold the temperature very steady, which is not what you're going to see in > the real world. In real world conditions, it is possible that a device > with very good temperature properties will perform better (less low > frequency "noise") than one with much better noise specs, but having > larger > temperature coefficients. > > Just an aside, but related, in building very long time-constant RC > filters, > say 1000sec or so, if you use the lowest leakage capacitors, the largest > noise source seems to be due to the variation of capacitor value with > temperature and is proportional to the DC voltage on the capacitor. The > capacitor charge Q=CV, and in the steady-state can be assumed to be > constant. If C goes down due to a temperature change, V goes up--and the > effect is fairly large. > > At very low frequencies, temperature effects look a lot like noise. > > Brett > > > At 08:57 PM 3/9/2005 -0500, you wrote: >>I am getting pretty deeply into the design process for a velocity coil >>seismometer amplifier and filter and have decided to try ot quantify >>the relative noise performance of various candidate opamps versus coil >>resistance. Here is the list of low noise and general purpose types >>(which I have on hand) that I am comparing: > > If my e-mail address above is not working > you can always reach my mail form at: http://bnordgren.org/contactB.html > using your Web browser. > > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: John Popelish jpopelish@........ Date: Thu, 10 Mar 2005 11:23:19 -0500 Jack Ivey wrote: > Bret Nordgren wrote: > >> Another factor that you may want to consider is thermal variation. At very >> low frequencies, below 1Hz, the effects of micro-variations in the device >> temperature can add additional "noise". (snip) > > I've seen this effect with thermocouple amplifiers, where moving your hand > near the circuit would move the air enough to create low-frequency noise. > It can be almost eliminated by pressing the circuit board between pieces > of foam rubber. It also helps a lot to keep the internal temperature rise of the front end opamp to a minimum. Reducing the opamp supply voltage as much as possible without degrading the performance of the amp helps keep the chip cool and reduce the thermal effect of changes in air currents. For this reason, if two amp choices have similar noise specs, but one may be operated at lower supply voltage or draws less supply current, its lower self heating may allow it to out perform its hotter competition in the low frequency realm. Thanks to both of you for reminding me of this subtlety. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op-Amps From: Douglas Gavilanes gavilan1@............. Date: Thu, 10 Mar 2005 15:37:12 -0800 psn-l-digest-request@.............. wrote: >.------ ------ ------ ------ ------ ------ ------ ------ ------ ------. >| Message 1 | >'------ ------ ------ ------ ------ ------ ------ ------ ------ ------' >Subject: Op amp front end noise >From: John Popelish >Date: Wed, 09 Mar 2005 20:57:24 -0500 > >I am getting pretty deeply into the design process for a velocity coil >seismometer amplifier and filter and have decided to try ot quantify >the relative noise performance of various candidate opamps versus coil >resistance. Here is the list of low noise and general purpose types >(which I have on hand) that I am comparing: > >AD706 >AD708 >AD820 >AD822 >ICL6750S >LF411 >LMC6062 >LMC6462 >LMC6482 >LT1007 >LI1115 >LT1124 >LT1128 >LT1677 >LT1047 >LTC1051 >LTC1151 >MAX400 >MAX410 >MAX420 >MAX427 >MAX430 >MCP6022 >OP07 >OP177 >OP2604 >OP27 >OP97 > >Do you have any suggestions for other candidates I might evaluate? > >My biggest difficulty in completing this task has been resolving the >wide variation in noise specifications for the various types to >produce a valid comparison in the DC to 10 Hz frequency range, >especially comparing the chopper types to the others. > > > You might try the OP80A, which is very low noise and has a high input impedance. A decent second could be the LF356, unless you're locked into another package. Just a thought. Of course, the OP80 is out of production now, I believe, but if you can find some, let me know! Seriously... Doug Gavilanes Garden Grove, CA. gavilan1@............. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: John Popelish jpopelish@........ Date: Thu, 10 Mar 2005 19:17:49 -0500 akr@......... wrote: > John and all others - > > I would add the quad OP-400 to the list. It is essentially a low power > quad OP-07/77. It also has the added advantage of being able to drive > large capacitive loads - I use it as a driver for the long cable run > leading from my seismograph to the AtoD card in my computer in addition to > using it for amplifying and filter applications. The data shows the > OP-400 driving a 1nF load without oscillation - I took the picture when > writing the OP-400 data sheet in my previous career in new product > development and applications at PMI/ADI (we were bought out by ADI in > 1990.) Cool! I will include it, but it pales in comparison to some of the quietest amplifiers as a front end, especially with low impedance sources. It looks fine for second and later stages of gain and filtering, though. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: John Popelish jpopelish@........ Date: Thu, 10 Mar 2005 19:20:23 -0500 George Bush wrote: > > I am building a mercury-cup tiltmeter and it uses the INA121 opamp. I would > be interested in seeing your analysis of it's noise also. I will include it in my survey, but it appears to be better with very high impedance signal sources. I am interested in how the tiltmeter connects to the amplifier. What sort of signal source impedance does this represent? Do you need the instrumentation amplifier differential configuration? -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op-Amps From: John Popelish jpopelish@........ Date: Thu, 10 Mar 2005 19:39:45 -0500 Douglas Gavilanes wrote: > You might try the OP80A, which is very low noise and has a high input > impedance. A decent second could be the LF356, unless you're locked > into another package. Just a thought. Of course, the OP80 is out of > production now, I believe, but if you can find some, let me know! > Seriously... Not only can't I find a source for the OP80A, I can't locate a data sheet. If you have a PDF datasheet file, you are welcome to email it to me. I will include the LF356 in the survey, because it is well suited for second and later filter stages where high value input resistors (low bias current and low current noise) may be involved and its fairly large offset voltage is not so important. It really needs nearly a full +-15 volt supply to produce a perfect +-10 volt output, though. There are others that do as well with a +-12 volt supply. I hope to produce a graphical comparison of many types that are optimum choices for various source impedances, at around 1 hertz (lower than the frequency considered in many comparison charts I have seen). That 1/f corner frequency where the noise starts to rise as frequency falls makes all the difference. Looks like I may have to build a web page. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: ChrisAtUpw@....... Date: Thu, 10 Mar 2005 19:39:30 EST In a message dated 10/03/2005, ke6pxp@....... writes: I am building a mercury-cup tiltmeter and it uses the INA121 opamp. I would be interested in seeing your analysis of it's noise also. Hi George, I don't know if you could tolerate an input current of 5 nano Amps, rather than 4 pico Amps? The INA118 has about 1/3 the 0.1 to 10 Hz voltage noise and about twice the CMRR range. This is the one that I use with differential photocells. Regards, Chris Chapman
In a message dated 10/03/2005, ke6pxp@....... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I am=20 building a mercury-cup tiltmeter and it uses the INA121 opamp. I would
= be=20 interested in seeing your analysis of it's noise=20 also.
Hi George,
 
    I don't know if you could tolerate an input cur= rent=20 of 5 nano Amps, rather than 4 pico Amps? The INA118 has abo= ut=20 1/3 the 0.1 to 10 Hz voltage noise and about twice the CMRR range. This is t= he=20 one that I use with differential photocells.
 
    Regards,
 
    Chris Chapman
Subject: Re: Op-Amps From: akr@......... Date: Thu, 10 Mar 2005 16:54:56 -0800 (PST) Doug and all - The OP-80 was PMI's first attempt at a CMOS op amp - hence the high input impedance. Other than that its spec's weren't that great compared to the other PMI op amps so those of us in marketing didn't think too much of it - we had a hard time getting our sales force to sell it because we couldn't give them too much guidance on how to sell it. More on the OP-400 - it wasn't meant to have the lowest noise because it was also a low power quad amp (op map voltage noise is directly related to the collector current in the input differential pair). The OP-470 was designed as a quad OP-27 and runs at several ma per device - everything in life is a tradeoff. Art > Douglas Gavilanes wrote: > >> You might try the OP80A, which is very low noise and has a high input >> impedance. A decent second could be the LF356, unless you're locked >> into another package. Just a thought. Of course, the OP80 is out of >> production now, I believe, but if you can find some, let me know! >> Seriously... > > Not only can't I find a source for the OP80A, I can't locate a data > sheet. If you have a PDF datasheet file, you are welcome to email it > to me. > > I will include the LF356 in the survey, because it is well suited for > second and later filter stages where high value input resistors (low > bias current and low current noise) may be involved and its fairly > large offset voltage is not so important. It really needs nearly a > full +-15 volt supply to produce a perfect +-10 volt output, though. > There are others that do as well with a +-12 volt supply. > > I hope to produce a graphical comparison of many types that are > optimum choices for various source impedances, at around 1 hertz > (lower than the frequency considered in many comparison charts I have > seen). That 1/f corner frequency where the noise starts to rise as > frequency falls makes all the difference. > > Looks like I may have to build a web page. > > -- > John Popelish > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: ChrisAtUpw@....... Date: Thu, 10 Mar 2005 20:33:08 EST In a message dated 10/03/2005 16:11:50 GMT Standard Time, jpopelish@........ writes: Jack Ivey wrote: > Bret Nordgren wrote: >> Another factor that you may want to consider is thermal variation. At very >> low frequencies, below 1Hz, the effects of micro-variations in the device >> temperature can add additional "noise". > I've seen this effect with thermocouple amplifiers, where moving your hand > near the circuit would move the air enough to create low-frequency noise. > It can be almost eliminated by pressing the circuit board between pieces > of foam rubber. It also helps a lot to keep the internal temperature rise of the front end opamp to a minimum. Reducing the opamp supply voltage as much as possible without degrading the performance of the amp helps keep the chip cool and reduce the thermal effect of changes in air currents. For this reason, if two amp choices have similar noise specs, but one may be operated at lower supply voltage or draws less supply current, its lower self heating may allow it to out perform its hotter competition in the low frequency realm. Hi John, Assuming that you are using a 16 bit ADC with a range of +/-10V, one count is 305 micro volts. Normal amplifier gains can result in very significant count drifts with temperature unless great care is taken in the design and construction. There are two different factors operating here. One is the temperature sensitivity of the opamp input circuit in micro V / C Deg. Remember that this relates to temperatures on the IC chip itself, so it is effected by the chip dissipation. The CAZ type opamps have very greatly reduced thermal input drifts and 1/f noise. The other is the signals derived from external thermo electric junctions and are rarely less than a few micro V / C Deg. These can be between the chip header and the socket or the wiring, or between cables and the input clamps, or even between different cables or connections. You will see differences across the circuit board, if there is a thermal gradient across it. Some resistors, like the metal oxide types, generate high EMFs if there is a temperature difference between the two ends. Don't even try to use carbon resistors, either composition or film. It can be an advantage to stick a strip of soft Al or Cu to the top, or even to both sides, of the input amplifier chip and bolt this onto the outer Al Screening Case. Another alternative is to use double sided circuit board. This greatly reduces temperature variations across the board. You can bolt a Cu chip cover strip onto the board. This is preferable to trying to reduce the dissipation by reducing the supply voltage. Having said this, it may be desirable to use separate IC regulators for the input opamp supply, to give low noise and drift and high AC supply rejection. The first amplifier does need very good supply noise decoupling. Seismometer amplifiers often have two distinct gain stages, with a high pass filter set to maybe 20 to 30 sec in between. This will greatly reduce thermal error signals and 1/f noise at the output. For geophone circuits, the filter maybe set to 1/10 the resonant frequency. The seismometer amplifier case is preferably made of metal and earthed. It should be kept dry, screened from drafts and any temperature variations should be minimised. It can be an advantage to fill the case with glass wool to inhibit convection. You might include the LF412 for second amplifiers. They have quite low drift. The INA118 is very useful as a low noise true differential input opamp. For information, noise calculation and selection of your photo diodes See _http://usa.hamamatsu.com/assets/applications/SSD/photodiode_technical_information.pdf_ (http://usa.hamamatsu.com/assets/applications/SSD/photodiode_technical_information.pdf) Regards, Chris Chapman
In a message dated 10/03/2005 16:11:50 GMT Standard Time,=20 jpopelish@........ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Jack=20 Ivey wrote:
> Bret Nordgren wrote:
>> Another factor that y= ou=20 may want to consider is thermal variation.  At very
>> low=20 frequencies, below 1Hz, the effects of micro-variations in the=20 device
>> temperature can add additional "noise".

> I'= ve=20 seen this effect with thermocouple amplifiers, where moving your hand
&= gt;=20 near the circuit would move the air enough to create low-frequency=20 noise.
> It can be almost eliminated by pressing the circuit board=20 between pieces
> of foam rubber.

It also helps a lot to keep=20= the=20 internal temperature rise of the front
end opamp to a minimum. =20 Reducing the opamp supply voltage as much as
possible without degrading= the=20 performance of the amp helps keep the
chip cool and reduce the thermal=20 effect of changes in air currents.

For this reason, if two amp choi= ces=20 have similar noise specs, but one
may be operated at lower supply volta= ge=20 or draws less supply current,
its lower self heating may allow it to ou= t=20 perform its hotter
competition in the low frequency=20 realm.
    Hi John,
 
    Assuming that you are using a 16 bit ADC with a= =20 range of +/-10V, one count is 305 micro volts. Normal amplifier gains can re= sult=20 in very significant count drifts with temperature unless great care is taken= in=20 the design and construction.
 
        There are two different= =20 factors operating here. One is the temperature sensitivity of the opamp inpu= t=20 circuit in micro V / C Deg. Remember that this relates to temperatures=20 on the IC chip itself, so it is effected by the chip dissipation.
 
    The CAZ type opamps have very greatly reduce= d=20 thermal input drifts and 1/f noise.
 
    The other is the signals derived from external=20 thermo electric junctions and are rarely less than a few micro V / C De= g.=20 These can be between the chip header and the socket or the wiring,=20 or between cables and the input clamps, or even between different cable= s or=20 connections. You will see differences across the circuit board, if there is=20= a=20 thermal gradient across it.
 
    Some resistors, like the metal oxide types,=20 generate high EMFs if there is a temperature difference between the two=20 ends. Don't even try to use carbon resistors, either composition or=20 film. 
 
    It can be an advantage to stick a strip of soft= Al=20 or Cu to the top, or even to both sides, of the input amplifier chip and bol= t=20 this onto the outer Al Screening Case. Another alternative is to use double=20 sided circuit board. This greatly reduces temperature variations across the=20 board. You can bolt a Cu chip cover strip onto the board. This is=20 preferable to trying to reduce the dissipation by reducing the supply voltag= e.=20 Having said this, it may be desirable to use separate IC regulators for the=20 input opamp supply, to give low noise and drift and high AC supply=20 rejection. The first amplifier does need very good supply noise decoupl= ing.=20
 
    Seismometer amplifiers often have two distin= ct=20 gain stages, with a high pass filter set to maybe 20 to 30 sec in between.=20 This will greatly reduce thermal error signals and 1/f noise at the out= put.=20 For geophone circuits, the filter maybe set to 1/10 the resonant=20 frequency.
 
    The seismometer amplifier case is preferably ma= de=20 of metal and earthed. It should be kept dry, screened from drafts and any=20 temperature variations should be minimised. It can be an advantage to f= ill=20 the case with glass wool to inhibit convection.
 
    You might include the LF412 fo= r=20 second amplifiers. They have quite low drift.
 
    The INA118 is very useful as a= low=20 noise true differential input opamp. 
 
    For information, noise calculation and=20 selection of your photo diodes See http://usa.hamamatsu.com/assets/applications/SSD/photodio= de_technical_information.pdf
 
    Regards,
 
    Chris Chapman
Subject: Re: Op amp front end noise From: John Popelish jpopelish@........ Date: Thu, 10 Mar 2005 21:03:10 -0500 > ChrisAtUpw@....... wrote: > jpopelish@........ writes: >> It also helps a lot to keep the internal temperature rise >> of the front end opamp to a minimum. Reducing the opamp >> supply voltage as much as possible without degrading the >> performance of the amp helps keep the chip cool and reduce >> the thermal effect of changes in air currents. (snip) > There are two different factors operating here. One is the > temperature sensitivity of the opamp input circuit in micro V / C > Deg. Remember that this relates to temperatures on the IC chip > itself, so it is effected by the chip dissipation. On this, we agree. > The CAZ type opamps have very greatly reduced thermal > input drifts and 1/f noise. No argument here, either. Eliminating the 1/f noise is essentially the reason they were invented. (snip advice on wiring, circuit board and resistor thermoelectric effects) > You can bolt a Cu chip cover strip onto the board. > This is preferable to trying to reduce the dissipation by > reducing the supply voltage. How so? Preferable for what reasons? > Having said this, it may be desirable > to use separate IC regulators for the input opamp supply, to give > low noise and drift and high AC supply rejection. The first > amplifier does need very good supply noise decoupling. Makes good sense to me. > Seismometer amplifiers often have two distinct gain stages, with > a high pass filter set to maybe 20 to 30 sec in between. This will > greatly reduce thermal error signals and 1/f noise at the output. > For geophone circuits, the filter maybe set to 1/10 the resonant > frequency. I am looking at using an integrator as negative feedback from the output back to the second or third stage to actively null the output drift, instead of putting a large capacitor in the forward signal path. This reduces the net offset to the offset of the integrator, instead of being the amplifier offset of the input where a series capacitor would normally be used. I think it is also easier to get a low noise, low frequency high pass corner frequency this way. Have you any criticism of this technique? > The seismometer amplifier case is preferably made of metal and > earthed. It should be kept dry, screened from drafts and any > temperature variations should be minimised. It can be an advantage > to fill the case with glass wool to inhibit convection. Agreed, but keeping all internal heat sources to a minimum should also help. > You might include the LF412 for second amplifiers. They have > quite low drift. I have included the equivalent LF411 in the survey. > The INA118 is very useful as a low noise true differential input > opamp. I'll add that. > For information, noise calculation and selection of your photo > diodes See > http://usa.hamamatsu.com/assets/applications/SSD/photodiode_technical_information.pdf I'll give it a read. This is the sort of thing I am designing at work. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Power supply questions From: "Randy" rpratt@............. Date: Thu, 10 Mar 2005 21:23:42 -0600 Has anyone operated the PSN amp filter on 5 - 6 volts? I recall someone on the list using 2 wall wart power supplies back to = back for the positive and negative supplies. Did you filter or = stabilize any further and if so how? Thank you for any advice. Randy
Has anyone operated the PSN amp filter = on 5 - 6=20 volts?
 
I recall someone on the list using 2 = wall wart=20 power supplies back to back for the positive and negative = supplies.  Did=20 you filter or stabilize any further and if so how?
 
Thank you for any advice.
 
Randy
Subject: Re: Power supply questions From: ChrisAtUpw@....... Date: Thu, 10 Mar 2005 22:56:56 EST In a message dated 11/03/2005, rpratt@............. writes: Has anyone operated the PSN amp filter on 5 - 6 volts? I recall someone on the list using 2 wall wart power supplies back to back for the positive and negative supplies. Did you filter or stabilize any further and if so how? Randy Dear Randy, Not successfully! The psn amplifiers have wall wort AC supplies recommended. This is rectified and +ve and -ve stabilised supply rails are generated on the boards. If you had looked at the equipment offered you would have seen this. Regards, /chris Chapman
In a message dated 11/03/2005, rpratt@............. writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
Has anyone operated the PSN amp filter on= 5 - 6=20 volts?
 
I recall someone on the list using 2 wall= wart=20 power supplies back to back for the positive and negative supplies. =20= Did=20 you filter or stabilize any further and if so how?
Randy
Dear Randy,
 
    Not successfully!
 
    The psn amplifiers have wall wort AC supplies=20 recommended. This is rectified and +ve and -ve stabilised supply rails are=20 generated on the boards. If you had looked at the equipment offered you woul= d=20 have seen this.
 
    Regards,
 
    /chris Chapman 
Subject: Re: Power supply questions From: "RANDY KIMBALL" randy.kimball@........... Date: Thu, 10 Mar 2005 22:38:30 -0600 Not really an answer to this question, but an FYI that I am using with = Larry's PSN boards. I found a discarded HP DeskJet power supply became useful again as the = PS for the Amp/filter stack and that the plug is the right size and = ready as if intended to fit. Another perfect find in the old junk = boxes, additional justification and fuel to the junk box growth habbit. -a different randy- ----- Original Message -----=20 From: Randy=20 To: psn-l@................. Sent: Thursday, March 10, 2005 9:23 PM Subject: Power supply questions Has anyone operated the PSN amp filter on 5 - 6 volts? I recall someone on the list using 2 wall wart power supplies back to = back for the positive and negative supplies. Did you filter or = stabilize any further and if so how? Thank you for any advice. Randy
Not really an answer to this question, = but an FYI=20 that I am using with Larry's PSN boards.
 
I found a discarded HP DeskJet power = supply became=20 useful again as the PS for the Amp/filter stack and that the plug is the = right=20 size and ready as if intended to fit.  Another perfect find in the = old junk=20 boxes, additional justification and fuel to the junk box = growth=20 habbit.
 
-a different = randy-
----- Original Message -----
From:=20 Randy=20
Sent: Thursday, March 10, 2005 = 9:23=20 PM
Subject: Power supply = questions

Has anyone operated the PSN amp = filter on 5 - 6=20 volts?
 
I recall someone on the list using 2 = wall wart=20 power supplies back to back for the positive and negative = supplies.  Did=20 you filter or stabilize any further and if so how?
 
Thank you for any = advice.
 
Randy
Subject: Re: Op amp front end noise From: ChrisAtUpw@....... Date: Fri, 11 Mar 2005 08:02:55 EST In a message dated 11/03/2005, jpopelish@........ writes: (snip advice on wiring, circuit board and resistor thermoelectric effects) > You can bolt a Cu chip cover strip onto the board. > This is preferable to trying to reduce the dissipation by > reducing the supply voltage. How so? Preferable for what reasons? Hi John, You are at most going to make a 50% reduction in the power, which is better controlled by efficient heat sinking. What you definitely do not want to do is to operate near the lower voltage limit with degraded performance and less 'headroom'. > Seismometer amplifiers often have two distinct gain stages, with > a high pass filter set to maybe 20 to 30 sec in between. This will > greatly reduce thermal error signals and 1/f noise at the output. I am looking at using an integrator as negative feedback from the output back to the second or third stage to actively null the output drift, instead of putting a large capacitor in the forward signal path. This reduces the net offset to the offset of the integrator, instead of being the amplifier offset of the input where a series capacitor would normally be used. I think it is also easier to get a low noise, low frequency high pass corner frequency this way. Have you any criticism of this technique? Yes. You will still see the large 1/f deviations at the output, which are of no interest and contain no information. You may find it difficult to make it stable over several opamps, especially if the gain is variable. If you want a sharper cutoff, why not use a two pole high pass filter? Regards, Chris Chapman
In a message dated 11/03/2005, jpopelish@........ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>(snip=20 advice on wiring, circuit board and resistor thermoelectric
effects)=20
> You can bolt a Cu chip cover strip onto the board.
> This=20= is=20 preferable to trying to reduce the dissipation by
> reducing the sup= ply=20 voltage.

How so?  Preferable for what reasons?
Hi John,
 
    You are at most going to make a 50% reduction i= n=20 the power, which is better controlled by efficient heat sinking. What you=20 definitely do not want to do is to operate near the lower voltage limit with= =20 degraded performance and less 'headroom'.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>>=20 Seismometer amplifiers often have two distinct gain stages, with
> a= =20 high pass filter set to maybe 20 to 30 sec in between. This will
>=20 greatly reduce thermal error signals and 1/f noise at the output.

I= am=20 looking at using an integrator as negative feedback from the
output bac= k to=20 the second or third stage to actively null the output
drift, instead of= =20 putting a large capacitor in the forward signal
path.  This reduce= s=20 the net offset to the offset of the integrator,
instead of being the=20 amplifier offset of the input where a series
capacitor would normally b= e=20 used.  I think it is also easier to get a
low noise, low frequency= =20 high pass corner frequency this way.  Have
you any criticism of th= is=20 technique?
    Yes. You will still see the large 1/f deviation= s at=20 the output, which are of no interest and contain no information. You may fin= d it=20 difficult to make it stable over several opamps, especially if the gain is=20 variable. If you want a sharper cutoff, why not use a two pole high pass=20 filter?
 
    Regards,
 
    Chris Chapman
Subject: RE: Power supply questions From: "John D Nelson" jnelson@................. Date: Fri, 11 Mar 2005 08:12:34 -0600 There is a lot of variance in "walwart" supplies. Some are AC out, some DC and a few DC regulated. Typically the dc ones are pretty poorly regulated due to really cheap transformers. I always make the assumption that the DC ones are pretty much unfiltered DC and add filtration and regulation accordingly. It is a good idea to check them to see if the rated current capability is really there by loading them down in a test. =20 =20 John Nelson =20 ________________________________ From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Randy Sent: Thursday, March 10, 2005 9:24 PM To: psn-l@.............. Subject: Power supply questions =20 Has anyone operated the PSN amp filter on 5 - 6 volts? =20 I recall someone on the list using 2 wall wart power supplies back to back for the positive and negative supplies. Did you filter or stabilize any further and if so how? =20 Thank you for any advice. =20 Randy

There is a lot of variance in = “walwart” supplies.  Some are AC out, some DC and a few DC regulated.  = Typically the dc ones are pretty poorly regulated due to really cheap transformers.  = I always make the assumption that the DC ones are pretty much unfiltered DC and = add filtration and regulation accordingly.  It is a good idea to check = them to see if the rated current capability is really there by loading them down in = a test. 

 

John = Nelson

 

From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Randy
Sent: Thursday, March 10, = 2005 9:24 PM
To: = psn-l@..............
Subject: Power supply = questions

 

Has anyone operated the PSN amp filter on 5 - 6 = volts?

 

I recall someone on the list using 2 wall wart power supplies back to back for the positive and negative supplies.  Did = you filter or stabilize any further and if so = how?

 

Thank you for any = advice.

 

Randy

Subject: Re: Op amp front end noise - termal variation control From: "Charles R. Patton" charles.r.patton@........ Date: Fri, 11 Mar 2005 09:51:33 -0800 Hi-stability oscillators use proportional oven control techniques such as a copper container that has a heater coil and sensing. Then the ckt is inside with some insulation. Very high quality variations of this do two containers with separate heaters and sensing – one inside the other with insulator between the containers. The idea is to have high thermal conductivity containers separated by insulation to reduce gradients and thermal transients. A cheaper variation would be to use aluminum pipe rather than copper – not as good in the thermal mass dept., but still pretty good thermal conductivity. There are lots of examples of these in the amateur radio community – see issues of QEX for several examples. A very simple way to reduce air current variation is to put your circuit in a small, open-top box and pour in clean, dry, sand. I like #30 silica sand (the fine, white sand you see in hotel lobby ash-tray cans), about $4 for a 50 lb. sack at Home Depot. Also helps with microphonics – if you have them. Just pour out the sand to work on the circuit. Regards, Charles Patton ChrisAtUpw@....... wrote: > >In a message dated 10/03/2005 16:11:50 GMT Standard Time, jpopelish@........ >writes: > >Jack Ivey wrote: > > >>Bret Nordgren wrote: >> >> >>>Another factor that you may want to consider is thermal variation. At >>> >>> >very > > >>>low frequencies, below 1Hz, the effects of micro-variations in the device >>>temperature can add additional "noise". >>> >>> > > > >>I've seen this effect with thermocouple amplifiers, where moving your hand >> near the circuit would move the air enough to create low-frequency noise. >>It can be almost eliminated by pressing the circuit board between pieces >>of foam rubber. >> >> > >It also helps a lot to keep the internal temperature rise of the front >end opamp to a minimum. Reducing the opamp supply voltage as much as >possible without degrading the performance of the amp helps keep the >chip cool and reduce the thermal effect of changes in air currents. > >For this reason, if two amp choices have similar noise specs, but one >may be operated at lower supply voltage or draws less supply current, >its lower self heating may allow it to out perform its hotter >competition in the low frequency realm. > > > >Hi John, > > Assuming that you are using a 16 bit ADC with a range of +/-10V, one >count is 305 micro volts. Normal amplifier gains can result in very significant >count drifts with temperature unless great care is taken in the design and >construction. > > There are two different factors operating here. One is the >temperature sensitivity of the opamp input circuit in micro V / C Deg. Remember that >this relates to temperatures on the IC chip itself, so it is effected by the >chip dissipation. > > The CAZ type opamps have very greatly reduced thermal input drifts and >1/f noise. > > The other is the signals derived from external thermo electric junctions >and are rarely less than a few micro V / C Deg. These can be between the >chip header and the socket or the wiring, or between cables and the input >clamps, or even between different cables or connections. You will see differences >across the circuit board, if there is a thermal gradient across it. > > Some resistors, like the metal oxide types, generate high EMFs if there >is a temperature difference between the two ends. Don't even try to use >carbon resistors, either composition or film. > > It can be an advantage to stick a strip of soft Al or Cu to the top, or >even to both sides, of the input amplifier chip and bolt this onto the outer >Al Screening Case. Another alternative is to use double sided circuit board. >This greatly reduces temperature variations across the board. You can bolt a >Cu chip cover strip onto the board. This is preferable to trying to reduce >the dissipation by reducing the supply voltage. Having said this, it may be >desirable to use separate IC regulators for the input opamp supply, to give low >noise and drift and high AC supply rejection. The first amplifier does need >very good supply noise decoupling. > > Seismometer amplifiers often have two distinct gain stages, with a high >pass filter set to maybe 20 to 30 sec in between. This will greatly reduce >thermal error signals and 1/f noise at the output. For geophone circuits, the >filter maybe set to 1/10 the resonant frequency. > > The seismometer amplifier case is preferably made of metal and earthed. >It should be kept dry, screened from drafts and any temperature variations >should be minimised. It can be an advantage to fill the case with glass wool to >inhibit convection. > > You might include the LF412 for second amplifiers. They have quite low >drift. > > The INA118 is very useful as a low noise true differential input opamp. > > For information, noise calculation and selection of your photo diodes >See >_http://usa.hamamatsu.com/assets/applications/SSD/photodiode_technical_information.pdf_ >(http://usa.hamamatsu.com/assets/applications/SSD/photodiode_technical_information.pdf) > > Regards, > > Chris Chapman > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise - termal variation control From: ChrisAtUpw@....... Date: Fri, 11 Mar 2005 20:26:11 EST In a message dated 11/03/2005, charles.r.patton@........ writes: Hi-stability oscillators use proportional oven control techniques such as a= =20 copper container that has a heater coil and sensing. Then the ckt is inside= =20 with some insulation. A cheaper variation would be to use aluminum pipe rat= her=20 than copper =E2=80=93 not as good in the thermal mass dept., but still prett= y good=20 thermal conductivity. Hi Charles, =20 The thermal mass per unit volume shows much less variation than one=20 might expect - 2.6 for Al and 3.5 for Cu. However, the thermal conductivity= may=20 be quite a bit lower for alloys than for pure metals. A lot of metal sold a= s=20 'Aluminum' is actually an Al + Silicon alloy. A very simple way to reduce air current variation is to put your circuit in= =20 a small, open-top box and pour in clean, dry, sand. I like #30 silica sand=20 (the fine, white sand you see in hotel lobby ash-tray cans), about $4 for a= 50=20 lb. sack at Home Depot. Also helps with microphonics =E2=80=93 if you have=20= them. Just=20 pour out the sand to work on the circuit. Do check to see that the sand is washed free of any salts. The circuit=20 board may be protected with a coat of single pack polyurethane varnish. Thi= s=20 melts under a soldering iron, so the circuit can be repaired if necessary.=20 Putting the board inside a thin polythene bag is an alternative to to varni= shing=20 and keeps sand out of any connectors, IC sockets. Another method is to fill the container with melted paraffin wax - at about= =20 58 C. This will make the circuit water proof and allows reasonably good=20 thermal contact. A mixture of half and half candle wax and bee's wax may al= so be=20 used, giving less shrinkage. =20 =20 Regards, =20 Chris Chapman
In a message dated 11/03/2005, charles.r.patton@........ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Hi-stability oscillators use proportional oven control techniques= such=20 as a copper container that has a heater coil and sensing. Then the ckt is=20 inside with some insulation. A cheaper variation would be to use aluminum=20= pipe=20 rather than copper =E2=80=93 not as good in the thermal mass dept., but st= ill pretty=20 good thermal conductivity.
Hi Charles,
 
    The thermal mass per unit volume shows much les= s=20 variation than one might expect - 2.6 for Al and 3.5 for Cu. However, the=20 thermal conductivity may be quite a bit lower for alloys than for pure=20 metals. A lot of metal sold as 'Aluminum' is actually an Al + Silicon=20 alloy.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>A very=20 simple way to reduce air current variation is to put your circuit in a sma= ll,=20 open-top box and pour in clean, dry, sand. I like #30 silica sand (the fin= e,=20 white sand you see in hotel lobby ash-tray cans), about $4 for a 50 lb. sa= ck=20 at Home Depot. Also helps with microphonics =E2=80=93 if you have them. Ju= st pour out=20 the sand to work on the circuit.
    Do check to see that the sand is washed free of= any=20 salts. The circuit board may be protected with a coat of single pack=20 polyurethane varnish. This melts under a soldering iron, so the circuit= can=20 be repaired if necessary. Putting the board inside a thin polythene bag is a= n=20 alternative to to varnishing and keeps sand out of any connectors, IC=20 sockets.

 
    Another method is to fill the container with me= lted=20 paraffin wax - at about 58 C. This will make the circuit water proof and all= ows=20 reasonably good thermal contact. A mixture of half and half candle wax and b= ee's=20 wax may also be used, giving less shrinkage.  
 
    Regards,
 
    Chris Chapman
Subject: Lowest noise opamps versus source resistance From: John Popelish jpopelish@........ Date: Fri, 11 Mar 2005 23:34:27 -0500 The following is a brief list of amplifiers ordered from lower noise to higher noise for a wide range of source resistances. This list was ordered based on the voltage and current effective input noise at 0.1 hertz the best I could extract those values from the data sheets. Please note that these are not all interchangeable, since some are singles, some are duals, most are opamps but some are instrumentation amplifiers (effectively 3 amplifiers set up as a high input impedance differential fixed gain amplifier), some are available in dip cases and some are available only in surface mount cases. Many operate from +- 15 volt supplies but some are low voltage units that work down to 2.7 volts, total, (including several of the best choices for the lower source resistances). So before you order any parts, down load the data sheets and make sure they are what you think they are. This represents several days of data sheet collection and data extraction. I hope it is some use to somebody besides me. Source 10 ohms LT1128 CS3001 CD3301 LT1007 MAX427 CS3011 LT1124 AD797 OP27 LT1115 AD708 Source 30 ohms LT1128 CS3001 CD3301 LT1007 MAX427 CS3011 LT1124 OP27 AD797 LT1115 AD708 Coil 100 ohms LT1128 CS3001 CD3301 LT1007 MAX427 CS3011 LT1124 OP27 AD797 LT1115 AD708 Source 300 ohms CS3001 CS3301 CS3011 LT1007 MAX427 LT1124 LT1128 OP27 OP270 LT1115 AD708 LT1677 Source 1k CS3001 CS3301 CS3011 LT1007 LT1124 OP27 OP270 AD708 MAX400 OP77 OP07 LT1677 OP97 LT1792 AD706 LT1013 Coil 3k ohms CS3001 CS3301 CS3011 AD708 LT1124 OP270 OP77 OP07 LT1007 OP27 LT1677 OP97 LT1792 AD706 LT1013 Coil 10k CS3001 CS3301 CS3011 OP177 AD708 OP07 OP77 OP97 MAX400 LT1792 AD706 LT1013 OP200 OP400 MAX430 MAX420 Source 30k CS3301 CS3001 CS3011 OP177 OP97 LT1792 AD706 AD708 OP07 OP77 LT1013 OP200 OP400 MAX430 MAX420 MAX400 Coil 100k CS3301 CS3001 CS3011 OP97 LT1792 AD706 MAX430 MAX420 LTC1151 LTC1051 CS3302 INA121 AD822 AD820 ICL7650S Coil 300k CS3301 OP97 CS3011 CS3001 LT1792 AD706 MAX430 MAX420 LTC1051 LTC1151 CS3302 INA121 AD820 AD822 Coil 1 Meg CS3301 LT1792 MAX430 MAX420 OP97 OP2604 OPA604 LTC1051 LTC1151 CS3302 INA121 ICL7650S AD820 AD822 LTC1047 Coil 3 Meg MAX430 MAX420 OP2604 OPA604 LTC1051 LTC1151 CS3302 CS3301 LT1792 ICL7650S AD820 AD822 INA121 OP97 LTC1047 Source 10 Meg MAX430 MAX420 OPA604 OP2604 LTC1051 LTC1151 ICL7650S LTC1047 AD820 AD822 CS3301 INA121 LMC6062 Coil 30 Meg OPA604 AD820 AD822 OP2604 MAX430 MAX420 ICL7650 LTC1047 LMC6062 AD820 AD822 CS3301 INA121 Source 100 Meg LTC1051 LTC1151 OPA604 LTC1047 OP2604 MAX430 MAX420 ICL7650S LMC6062 AD820 AD822 CS3301 INA121 -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: George Bush ke6pxp@....... Date: Sat, 12 Mar 2005 10:00:09 -0800 At 07:20 PM 3/10/05 -0500, you wrote: >George Bush wrote: >> >> I am building a mercury-cup tiltmeter and it uses the INA121 opamp. I would >> be interested in seeing your analysis of it's noise also. > >I will include it in my survey, but it appears to be better with very >high impedance signal sources. Yes, the tiltmeter application is high impedance differential. >I am interested in how the tiltmeter >connects to the amplifier. What sort of signal source impedance does >this represent? Do you need the instrumentation amplifier >differential configuration? It uses RF connected to the mercury to excite antenna plates just above two connected pools 24" apart. The antenna signals are detected (rectified) and fed into the INA121 in a differential configuration. The DC impedance is high (back impedance of the diodes), but since they are charging .1 uf caps, the AC impedance is low. The mechanical design is old and originally appeared in an early 1970's "Scientific American" Amatuer Scientist article "A Sensitive mercury tiltmeter that serves as a seismometer". I still have a copy of the pages (pp. 124-129), but SA didn't print the date on the pages. Recently Ron Newton modernized the electronics and published an article on the May 2003 "Nuts n Volts" magazine, pp. 47-51, "Measure Earth Tides with a Tiltometer" I appreciate the OP-amp survey that you are doing, it will really help in the construction of ametuer seismometers. > >-- >John Popelish >__________________________________________________________ > >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. > George Bush Sea Ranch, CA, USA 38.73775N, 123.48882W __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: John Popelish jpopelish@........ Date: Sat, 12 Mar 2005 13:55:04 -0500 George Bush wrote: > > John Popelish wrote: > >I am interested in how the tiltmeter > >connects to the amplifier. (snip) > It uses RF connected to the mercury to excite antenna plates just above > two connected pools 24" apart. The antenna signals are detected (rectified) > and fed into the INA121 in a differential configuration. The DC impedance > is high (back impedance of the diodes), but since they are charging .1 uf > caps, the AC impedance is low. The mechanical design is old and originally > appeared in an early 1970's "Scientific American" Amatuer Scientist article > "A Sensitive mercury tiltmeter that serves as a seismometer". I still have > a copy of the pages (pp. 124-129), but SA didn't print the date on the > pages. Recently Ron Newton modernized the electronics and published an > article on the May 2003 "Nuts n Volts" magazine, pp. 47-51, "Measure Earth > Tides with a Tiltometer" If you have a scanner, I would very much like to get a look at those articles. I have a big email inbox. Perhaps we can get permission to copy them on a web page. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: From: apsn apsn@........... Date: Sat, 12 Mar 2005 14:07:24 -0900 unsubscribe __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: Ben Bradley benbradley@............... Date: Sat, 12 Mar 2005 19:58:13 -0500 George Bush wrote: > ... > caps, the AC impedance is low. The mechanical design is old and originally > appeared in an early 1970's "Scientific American" Amatuer Scientist article > "A Sensitive mercury tiltmeter that serves as a seismometer". I still have > a copy of the pages (pp. 124-129), but SA didn't print the date on the > pages. That article ia dated November, 1973. I've got the whole collection of Amateur Scientist columns on CD from . I think this is a great deal for $29 and recommend it highly, even though several of the early articles are just descriptions and pictures of amateur-made telescopes and how that hobby was growing at the time, with very little technical info. The articles in the most recent five decades more than make up for the earlier ones. > Recently Ron Newton modernized the electronics and published an > article on the May 2003 "Nuts n Volts" magazine, pp. 47-51, "Measure Earth > Tides with a Tiltometer" > > I appreciate the OP-amp survey that you are doing, it will really help in > the construction of ametuer seismometers. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise / tiltmeter From: ChrisAtUpw@....... Date: Sat, 12 Mar 2005 21:47:12 EST In a message dated 12/03/2005, ke6pxp@....... writes: At 07:20 PM 3/10/05 -0500, you wrote: >George Bush wrote: >> I am building a mercury-cup tiltmeter and it uses the INA121 opamp. I would >> be interested in seeing your analysis of it's noise also. >I am interested in how the tiltmeter connects to the amplifier. What sort of signal >source impedance does this represent? Do you need the instrumentation amplifier >differential configuration? It uses RF connected to the mercury to excite antenna plates just above two connected pools 24" apart. The antenna signals are detected (rectified) and fed into the INA121 in a differential configuration. The DC impedance is high (back impedance of the diodes), but since they are charging .1 uf caps, the AC impedance is low. The mechanical design is old and originally appeared in an early 1970's "Scientific American" Amatuer Scientist article "A Sensitive mercury tiltmeter that serves as a seismometer". I still have a copy of the pages (pp. 124-129), but SA didn't print the date on the pages. Recently Ron Newton modernized the electronics and published an article on the May 2003 "Nuts n Volts" magazine, pp. 47-51, "Measure Earth Tides with a Tiltometer" George Bush Sea Ranch, CA, USA 38.73775N, 123.48882W Hi George, The circuit in _http://www.nutsvolts.com/toc_Pages/may03toc.htm_ (http://www.nutsvolts.com/toc_Pages/may03toc.htm) seems to be flawed. It appears to depend on the reverse leakage current of the rectifier diodes to provide the DC level stability and this is both variable and highly temperature dependant. A resistor needs to be connected across both capacitors to provide a fixed impedance to earth. You do need a true differential opamp for this type of circuit to get the very high CMRR required. The inherent weakness of this type of circuit is that the properties of the tuned circuits and the diodes are temperature sensitive and this limits both the accuracy and the drift. The temperature drift on a Si diode is about 2.5 milli V /C Deg. I note that there is no low pass filter at the amplifier output! This will allow greatly increased output noise. An INA118 amplifier could give better performance. This type of circuit was used on seismometers for a short period during the 1970s before being replaced by fet switch technology. Short length tiltmeters are also sensitive to surface ground heave, wind noise and to movements caused by temperature and rain / ground water level changes. There is now absolutely NO necessity to go to such high frequencies (4 MHz), or to use resonant circuits and diodes, to generate highly sensitive displacement signals using moving capacitor plates. This can be done quite easily at about 20 KHz using fet switches. See "Bridge Measures Small Capacitance" by Jeff Witt, Linear Technology Corp, in Electronic Design, Nov. 4, 1996, pg. 110. This is also available on the Linear Technology site in the second circuit compendium and uses the LTC1043 quad switch / oscillator. DO NOTE that liquid mercury has an appreciable vapour pressure at room temperature and that the vapour is highly toxic. It will also react strongly with many metals giving 'amalgams', which 'corrode' the surface. Both Copper and Aluminum are highly susceptible. Steel and glass may be used for the containment. Mercury is very dense and quite expensive. Details of more modern tiltmeters are given in papers and references by Nicolas d'Oreye at the Walferdange site. Type Walferdange tiltmeter or seismometer into _www.google.com_ (http://www.google.com) See _http://www.ecgs.lu/index.php?option=displaypage&Itemid=51&op=page&SubMenu_ (http://www.ecgs.lu/index.php?option=displaypage&Itemid=51&op=page&SubMenu) Water with a layer of silicone oil on top has also been used very successfully in tiltmeters. The silicone oil prevents evaporation and condensation problems with the water. The high dielectric constant of water vs the low value for oil, is a great help. If you can find the full reference for the Sci Am article, you ought to be able to get a photocopy through your local library, although this may take a couple of weeks. Regards, Chris Chapman
In a message dated 12/03/2005, ke6pxp@....... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>At 07:20=20 PM 3/10/05 -0500, you wrote:
>George Bush wrote: 
>> I= am=20 building a mercury-cup tiltmeter and it uses the INA121 opamp. I=20 would
>> be interested in seeing your analysis of it's noise=20 also.

>I am interested in how the tiltmeter connects to the=20 amplifier.  What sort of signal >source impedance does this=20 represent?  Do you need the instrumentation amplifier
>differen= tial=20 configuration?

    It uses RF connected to the mercury to= =20 excite antenna plates just above
two connected pools 24" apart. The ant= enna=20 signals are detected (rectified)
and fed into the INA121 in a different= ial=20 configuration. The DC impedance
is high (back impedance of the diodes),= but=20 since they are charging .1 uf
caps, the AC impedance is low. The mechan= ical=20 design is old and originally
appeared in an early 1970's "Scientific=20 American" Amatuer Scientist article
"A Sensitive mercury tiltmeter that= =20 serves as a seismometer". I still have
a copy of the pages (pp. 124-129= ),=20 but SA didn't print the date on the
pages. Recently Ron Newton moderniz= ed=20 the electronics and published an
article on the May 2003 "Nuts n Volts"= =20 magazine, pp. 47-51, "Measure Earth
Tides with a Tiltometer"

Geo= rge=20 Bush
Sea Ranch, CA, USA
38.73775N, 123.48882W
Hi George,
 
    The circuit in http://www.nutsvolt= s.com/toc_Pages/may03toc.htm seems=20 to be flawed. It appears to depend on the reverse leakage current of th= e=20 rectifier diodes to provide the DC level stability and this is both variable= and=20 highly temperature dependant. A resistor needs to be connected across b= oth=20 capacitors to provide a fixed impedance to earth. You do need a true=20 differential opamp for this type of circuit to get the very high CMRR requir= ed.=20
    The inherent weakness of this type of circuit i= s=20 that the properties of the tuned circuits and the diodes are temperature=20 sensitive and this limits both the accuracy and the drift. The temperature d= rift=20 on a Si diode is about 2.5 milli V /C Deg. I note that there is no low pass=20 filter at the amplifier output! This will allow greatly increased output noi= se.=20 An INA118 amplifier could give better performance. This type of circuit was=20= used=20 on seismometers for a short period during the 1970s before being replaced by= fet=20 switch technology.
    Short length tiltmeters are also sensitive to=20 surface ground heave, wind noise and to movements caused by temperature= and=20 rain / ground water level changes. 
    There is now absolutely NO necessity to go to s= uch=20 high frequencies (4 MHz), or to use resonant circuits and diodes, to generat= e=20 highly sensitive displacement signals using moving capacitor plates. Th= is=20 can be done quite easily at about 20 KHz using fet switches. See "Bridg= e=20 Measures Small Capacitance" by Jeff Witt, Linear Technology Corp, in Electro= nic=20 Design, Nov. 4, 1996, pg. 110. This is also available on the Linea= r=20 Technology site in the second circuit compendium and uses the LTC1043 q= uad=20 switch / oscillator. 
    DO NOTE that liquid mercury has an appreciable=20 vapour pressure at room temperature and that the vapour is highly toxic.=20 It will also react strongly with many metals giving 'amalgams', which 'corro= de'=20 the surface. Both Copper and Aluminum are highly susceptible. Steel a= nd=20 glass may be used for the containment. Mercury is very dense and q= uite=20 expensive.
    Details of more modern tiltmeters are given&nbs= p;in=20 papers and references by Nicolas d'Oreye at the Walferdange site. Type=20 Walferdange tiltmeter or seismometer into www.google.com See http://www.ecgs.lu/index.php?option=3Ddisplaypage&a= mp;Itemid=3D51&op=3Dpage&SubMenu Water=20 with a layer of silicone oil on top has also been used very successfully in=20 tiltmeters. The silicone oil prevents evaporation and condensation problems=20= with=20 the water. The high dielectric constant of water vs the low value for oil, i= s a=20 great help.
    If you can find the full reference for the Sci=20= Am=20 article, you ought to be able to get a photocopy through your local library,= =20 although this may take a couple of weeks.
    
    Regards,
 
    Chris Chapman
Subject: Thanks for tiltmeter help/info From: George Bush ke6pxp@....... Date: Sun, 13 Mar 2005 12:56:32 -0800 I was not planning on mentioning the tiltmeter to the list until I got some construction pictures on my website. But when John Popelish requested additions to his list to study I submitted the INA121 used on the tiltmeter to add to the list for for evaluation. Thank all of the rest of you for your comments. John requested more information on how the INA121 was used in the tiltmeter, so I sent a schematic and the two references. Thank you who offered info on getting these references. I have the original pages I tore out of the Scientific American back when I subscribed, and same for the Nuts n Volts article. I also have the Ametuer Scientist CD and have used it to "mine" many articles on seismometers and wierd pendulums. I would recommend it as a resource to anyone interested in constructing seismometers. Chris Chapman wrote: >Hi George, > > The circuit in http://www.nutsvolts.com/toc_Pages/may03toc.htm seems to be flawed. It appears to depend on the reverse leakage current of the rectifier diodes to provide the DC level stability and this is both variable and highly temperature dependant. A resistor needs to be connected across both capacitors to provide a fixed impedance to earth. You do need a true differential opamp for this type of circuit to get the very high CMRR required. > The inherent weakness of this type of circuit is that the properties of the tuned circuits and the diodes are temperature sensitive and this limits both the accuracy and the drift. The temperature drift on a Si diode is about 2.5 milli V /C Deg. I note that there is no low pass filter at the amplifier output! This will allow greatly increased output noise. An INA118 amplifier could give better performance. This type of circuit was used on seismometers for a short period during the 1970s before being replaced by fet switch technology. > Chris, I appreciate your comments about the toxicity of mercury and I will be taking appropriate steps to minimize exposure (instrument will be located in the garage, ventalated and away from human habitation). I also appreciate your comments about the circuit as I have not been able to get it to work. I have experienced high frequency "ringing" on the two cables from the antennas to the detectors, very high output noise (.5v.), grounding problems, noise on power busses, sensitivity to light (I suspect the diodes), and capacitive sensitivity if I bring a hand near the cables that connect to the cup antennas. I was planning on changing the topology of the circuit and separating the osc into a metal box, same for the amp, and put the detectors into the antennas on top of the cups. I may be better off in investigating another circuit. I will now start to look for circuit information on capacitance-based seismometer position sensors. I am delighted to see the tiltmeter interest and will report my progress to the list. George __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Thanks for tiltmeter help/info From: ChrisAtUpw@....... Date: Sun, 13 Mar 2005 19:16:58 EST
            = ;
 Subject: Re: Op amp front end noise From: ChrisAtUpw@....... Date: Mon, 14 Mar 2005 11:05:47 EST > John Popelish wrote: Hi John, You might take a look at:- Op Amp Selection Guide for Optimum Noise Performance _http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1009,C1021,P2 440,D6539_ (http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1009,C1021,P2440,D6539) See also _www.linear.com_ (http://www.linear.com/) AN87 pp87-89 BRIDGE MEASURES SMALL CAPACITANCE IN PRESENCE OF LARGE STRAYS by Jeff Witt. It should work fine with seismometer capacitor plates, but will need a low pass output filter added. Regards, Chris Chapman
> John Popelish wrote:
 
Hi John,
 
    You might take a look at:-
 
    Op Amp Selection Guide for Optimum Noise=20 Performance
http://www.linear.com/pc/downloadDocument.do?navId=3DH= 0,C1,C1154,C1009,C1021,P2440,D6539
 
     See also www.linear.com AN87 pp87-89 BRIDGE MEASU= RES=20 SMALL CAPACITANCE
IN PRESENCE OF LARGE STRAYS by Jeff Witt. It should wor= k=20 fine with seismometer capacitor plates, but will need a low pass output filt= er=20 added.
 
    Regards,
 
    Chris Chapman
 Subject: Re: Op amp front end noise From: John Popelish jpopelish@........ Date: Mon, 14 Mar 2005 12:05:05 -0500 > ChrisAtUpw@....... wrote: > You might take a look at:- > > Op Amp Selection Guide for Optimum Noise Performance > http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1009,C1021,P2440,D6539 I have this, but am trying to be able to reproduce it from the data sheets (so far, I think my results do not contradict this, so I think I am doing it right), and referenced to the much lower frequency range we need, as well as include other brands. Something interesting to me that does not show up in the list I posted, but in the graphs is the fact that the overall signal to noise ratio climbs as the coil wire size is reduced, even though it results in more resistive noise. But some opamps have such low current noise and the extra turns provide more signal voltage, so that there is a steady climb in signal to noise ratio to coil resistances around 100k, and then there is a second, even bigger peak for coil resistances of 100 meg ohms, but I wouldn't want to handle the wire. ;-) But the graph does show that there is signal to noise value in going with the smallest size wire you can deal with. > See also www.linear.com AN87 pp87-89 BRIDGE MEASURES SMALL > CAPACITANCE > IN PRESENCE OF LARGE STRAYS by Jeff Witt. It should work fine with > seismometer capacitor plates, but will need a low pass output filter > added. Will do. Thanks. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: PSN-Shackleford-Gundersen Seismometer Electronics Board From: George Bush ke6pxp@....... Date: Mon, 14 Mar 2005 21:23:25 -0800 Larry- As you have probably noticed on the list, I am having problems getting the circuit board working for the tiltmeter I am building. The Shackleford-Gundersen Seismometer capacitive displacement detector looks like it would work quite well on the mercury-cup tiltmeter I am building. Have you had any experience with using your board to detect mercury pool displacements? It seems like they should have about the same capacatance and spacing as the S-G instrument. I would appreciate your thoughts as I am very frustrated with the present circuit board from the Nuts n Volts Tiltometer article. George __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Op amp front end noise From: ChrisAtUpw@....... Date: Tue, 15 Mar 2005 11:12:13 EST In a message dated 14/03/2005 16:53:43 GMT Standard Time, jpopelish@........ writes: Something interesting to me that does not show up in the list I posted, but in the graphs is the fact that the overall signal to noise ratio climbs as the coil wire size is reduced, even though it results in more resistive noise. But some opamps have such low current noise and the extra turns provide more signal voltage, so that there is a steady climb in signal to noise ratio to coil resistances around 100k, and then there is a second, even bigger peak for coil resistances of 100 meg ohms, but I wouldn't want to handle the wire. Hi John, The opamps have a design impedance when the current and voltage noise levels are about equal. If the coil resistance is less than this, it pays to add turns. Are you taking the 1/f noise into account? This is usually fairly critical for seismic sensors, particularly when you are considering long period types. But the graph does show that there is signal to noise value in going with the smallest size wire you can deal with. It will usually pay to choose a fairly low amplifier impedance for inductive systems. The coils are much easier to make and physically smaller, which allows you to take full advantage of the very high fields that can be produced by 'modern' NdFeB magnet systems. The larger the coil, the more difficult it is to screen it from environmental noise. In general, most of us do not have the luxury of quiet seismic sites. The larger the inductance, the more susceptible is the wiring to picking up stray signals. It can pay to put a ceramic capacitor across the input to the opamp. The use of screened cable with a large dielectric loss can be an advantage. Regards, Chris Chapman
In a message dated 14/03/2005 16:53:43 GMT Standard Time,=20 jpopelish@........ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Something interesting to me that does not show up in the list I p= osted,=20 but in the graphs is the fact that the overall signal to noise ratio climb= s as=20 the coil wire size is reduced, even though it results in more resistive=20 noise.  But some opamps have such low current noise and the extra tur= ns=20 provide more signal voltage, so that there is a steady climb in signal to=20 noise ratio to coil resistances around 100k, and then there is a second, e= ven=20 bigger peak for coil resistances of 100 meg ohms, but I
wouldn't want t= o=20 handle the wire. 
Hi John,
 
    The opamps have a design impedance when the cur= rent=20 and voltage noise levels are about equal. If the coil resistance is less tha= n=20 this, it pays to add turns. 
 
    Are you taking the 1/f noise into account? This= is=20 usually fairly critical for seismic sensors, particularly when you are=20 considering long period types.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>But the=20 graph does show that there is signal to noise value in going
with the=20 smallest size wire you can deal with.
    It will usually pay to choose a fairly low=20 amplifier impedance for inductive systems. The coils are much easier to make= and=20 physically smaller, which allows you to take full advantage of the very high= =20 fields that can be produced by 'modern' NdFeB magnet systems.
 
    The larger the coil, the more difficult it=20= is to=20 screen it from environmental noise. In general, most of us do not have the=20 luxury of quiet seismic sites. The larger the inductance, the more susceptib= le=20 is the wiring to picking up stray signals. It can pay to put a ceramic capac= itor=20 across the input to the opamp. The use of screened cable with a large dielec= tric=20 loss can be an advantage.
 
    Regards,
 
    Chris Chapman

 Subject: Re: Op amp front end noise From: John Popelish jpopelish@........ Date: Tue, 15 Mar 2005 12:05:01 -0500 > ChrisAtUpw@....... wrote: > > John Popelish wrote: > > Something interesting to me that does not show up in the > > list I posted, but in the graphs is the fact that the > > overall signal to noise ratio climbs as the coil wire size > > is reduced, even though it results in more resistive > > noise. But some opamps have such low current noise and > > the extra turns provide more signal voltage, so that there > > is a steady climb in signal to noise ratio to coil > > resistances around 100k, and then there is a second, even > > bigger peak for coil resistances of 100 meg ohms, but I > > wouldn't want to handle the wire. > > The opamps have a design impedance when the current and voltage > noise levels are about equal. If the coil resistance is less than > this, it pays to add turns. Agreed. Processing the opamp data to take the turns count (in a given winding volume) into account and displaying this graphically makes this very clear. I need to get set up to post these pictures to the web. > Are you taking the 1/f noise into account? This is usually > fairly critical for seismic sensors, particularly when you are > considering long period types. Yes. I selected or extrapolated all device specs to 0.1 hertz for this comparison. Amplifiers that have a low 1/f corner frequency or chopper amps that actively correct 1/f noise do better in this range than if you compare amplifiers at higher frequencies. I selected this frequency as representative of what long period instruments measure. > > But the graph does show that there is signal to noise > > value in going with the smallest size wire you can deal with. > > It will usually pay to choose a fairly low amplifier impedance > for inductive systems. The coils are much easier to make and > physically smaller, which allows you to take full advantage of the > very high fields that can be produced by 'modern' NdFeB magnet > systems. My list is valid for any signal source, but the rising signal to noise effect with impedance mentioned in that last paragraph refers to coils that fit in a given volume. This implies that doubling the turns count raises the DC resistance by a factor of 4. > The larger the coil, the more difficult it is to screen it from > environmental noise. My comments referred to coils of similar dimensions. > In general, most of us do not have the luxury > of quiet seismic sites. The larger the inductance, the more > susceptible is the wiring to picking up stray signals. This is a separate problem. I think it is a good idea to electrostatically shielded any pickup coil. And the inductive pickup problem can be addresses with a hum bucking coil design. I am presently in the middle of building a dual voice coil pickup that is an attempt to buck out the effect of any external magnetic field changes, like those from power distribution, lightning strikes and aurora. I finally got my 6 iron pole pieces from the machine shop and assembled them with 20 ferocious NeFeB magnets. I am creating the coil bobbin now. The Lehman pendulum is almost done and I may have everything but the amplifier together by April fools day. > It can pay to put a ceramic capacitor across the input to the opamp. I concur about the capacitor, but you have to be careful with ceramics. Some of them are quite microphonic, especially the larger values in the high K class, like Y5V and Z5U. I think I prefer film capacitors. I also like a pair of non light sensitive diodes across the input to protect the front end from static when wires are not connected or excessive generated voltage when the coil is bumped. > The use of > screened cable with a large dielectric loss can be an advantage. I think there is value in getting at least the first stage of amplification close to the coil, to lower the chance of stray signals getting into the input. I may mount the whole amplifier-filter right beside the pendulum. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: The coil has been wound! From: John Popelish jpopelish@........ Date: Sat, 19 Mar 2005 19:24:04 -0500 After a week of bobbin making and winder preparation, and with lots of help from my wife counting off the turns at the hundreds beeper, my dual voice coil is wound and terminated. It consists of two coils, each 3/4" wide, ID of about 1.1" and OD about 1.4" and they are separated by 3/4". The spool says 44 ga., but it measures only 2 mils, insulation included, so it is a bit small. Each coil has 32,000 turns for a total of 64,000 turns and a total resistance of 90,500 ohms. By wire table, that works out to about 6.6 miles of 44 ga., but by physical size, it comes out to about 4 miles. This also makes me think that the wire is a bit smaller than 44 ga., or it became smaller after I stretched it to make the spool turn. :) About 7/8th of the way to the end, I broke the wire and had to solder a splice to be buried in the coil. Talk about having big hands and crude tools! Next step is to add the support rods that hold it up inside the magnet structure and seal the whole thing in a protective layer of wax. Then I can exhale. I am looking forward to measuring the sensitivity in volts seconds per meter, to see how it this design measures up, compared to others that I have been reading about. The highest sensitivity unit I have seen has a sensitivity of over 2400 volt seconds per meter. See HS-10-1 @ 210,000 ohms also with a dual coil. http://www.geosys.co.jp/GEO/Sensor/hs-10.html -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: The coil has been wound! From: John Popelish jpopelish@........ Date: Sat, 19 Mar 2005 21:40:43 -0500 > ChrisAtUpw@....... wrote: > In a message dated 20/03/2005, jpopelish@........ writes: > > > Next step is to add the support rods that hold it up > > inside the magnet structure and seal the whole thing > > in a protective layer of wax. > > Can you not use it dry as wound? Sure. But I am afraid it might bump the wire while assembling the magnet structure or while aligning the pendulum. This wire is so fragile that a bump could easily nick or break the wire. > Try hot candle wax? (snip) That is what the phrase, "protective layer of wax" refers to. I will probably dunk the whole thing in a cup of melted paraffin and wipe all of it off, except for over the coils. The wire is supposed rated for 140 C. > It is the linear motion output which is of interest. I use much > smaller ready wound coils with flat quad magnets. What is the self > resonant frequency of your coils in their magnet housing? (snip) I haven't tried to predict this but will measure the characteristics (both electrical resonance of the coil inductance with its and the cable capacitance and the pendulum resonance after the magnets are mounted on the pendulum and aligned around the coil. > I use a small coil winder with a five figure digital counter - a > magnet and a reed relay. The very large coils that I used to use > were made by dipping a wood former in hot wax, turning it off in a > lathe and then adding a paper layer and cloth layers + polyester > resin. I then turned off the cloth to give a slotted coil with a ~10 > thou substrate. After winding the coil, I warmed the whole thing > with a hair dryer to soften the wax and slid the coil off the wood > former. It was a bit fiddly, but satisfactory. The largest coil that > I wound was about 80,000 turns and took a week to finish. It was > used to measure paramagnetic susceptability at a low magetic field. (snip) Sounds like a gem. Mine took my wife and me about 4 hours to wind, but a half hour was used up making the splice. If I was going to make many more, I would build a much better winder and counter. This time I had a Rube Goldberg arrangement of a variable DC supply driving a small DC motor that turned the coil and a worm drive that turned a gear once avery 100 turns. I glued a small brass flag under that gear and had that pass over two wires to complete a circuit with a piezo speaker and a signal generator. This gave a ray gun blast once every 100 turns, and my wife ticked those off for me (320 of them for each half of the coil). I had to rig up a ball bearing shaft to hold the 1 pound spool or the wire would break before moving the spool. I had to move the spool 6 feet away from the winder so that the wire could absorb the bumps and surges without exceeding its elastic limit. Found that out with 4 attempts that got to only a few hundred turns and two that almost made it to 3000 turns. I found that a wet or dry vacuum cleaner made a nice sucker gun to pull the wire off while the spool was run backwards at high speed to prepare for another attempt. I sat and guided the wire back and forth with two fingers (wrapped in teflon thread tape, at my wife's suggestion, because the friction of a finger tip slowed the winding and added more tension to the wire), using a bright reflection off the top of the build to see whether things were flat and even or not. An automatic lay down mechanism would have been nice. But I am satisfied that I broke that red hair only once in 4 miles. -- John Popelish __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: 2 ebay auctions From: BOB BARNS royb1@........... Date: Sun, 20 Mar 2005 11:05:28 -0500 Nimbus Instruments signal enhancement seismograph ES125 Item number: 7502065715 ends Mar 26 SOILTEST PORTABLE ENGINEERING SEISMOGRAPH MD-5 SURVEY Item number: 7502107292 ends Mar 29 I know nothing about these. Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: 2 ebay auctions From: "Doug Crice" dcrice@............ Date: Sun, 20 Mar 2005 18:26:08 -0800 These are both what we in exploration geophysics would call refraction seismographs. You use them with a sledgehammer energy source and a = single geophone. You hit an aluminum plate located distance x from the = geophone and measure the time required for the P waves to get to the geophone. Then you move out 2x and repeat the experiment, and then 3x and so = forth. You draw a graph of time vs distance. As you go further out, the waves travel down through harder layers (because it's a quicker path) and the slope of your line changes. Typically there will be 3 or more layers, = e.g. soil, weathered rock, clay, or water table, and then bedrock. From the slope of the line on the graph you can calculate velocity, which tells = you something about the type of material. From the intercepts, you can calculate depth. You can download a manual on engineering seismic at ftp://geom.geometrics.com/pub/seismic/Literature/s-tr2.pdf If the link doesn't work, go to http://www.geometrics.com/Literature/literature.html register and look around for the Redpath book and other interesting stuff. The Geometrics unit is I think still supported. I'm not sure about the Soiltest unit. You would need some accessories to use it, a hammer = switch, a geophone, a metal plate, and a way to charge the battery. I was a = founder of Nimbus Instruments, so I could offer advice. The soiltest unit looks complete. Doug Crice http://www.georadar.com/geostuff.htm Wireless Seismic http://www.wirelessSeismic.com 12996 Somerset Drive phone 1-530-274-4445 Grass Valley, CA 95945 USA fax 1-530-274-4446 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of BOB BARNS Sent: Sunday, March 20, 2005 8:05 AM To: psn mail Subject: 2 ebay auctions Nimbus Instruments signal enhancement seismograph ES125 Item number:=20 7502065715 ends Mar 26 SOILTEST PORTABLE ENGINEERING SEISMOGRAPH MD-5 SURVEY Item number:=20 7502107292 ends Mar 29 I know nothing about these. Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismic recorders and geophones available - free to a good home From: Larry Cochrane lcochrane@.............. Date: Mon, 21 Mar 2005 14:26:34 -0800 Hi Everyone, I received this email the other day. The geophones are not very useful for earthquake recording since they are 8 hz units. Since Stanford is near by I could pick up and ship some units to people who are interested in having one of the records and/or sensors. I have no idea how big the records are so I have no idea what the shipping costs would be. Regards, Larry Cochrane Redwood City, PSN Simon Klemperer wrote: > Gray Jensen (USGS) suggested that you might have an interest, or know > of someone who might have an interest, in industry geophones. > Simon Klemperer > > > Subject: Seismic recorders and geophones available - free to a good home > > Stanford University is disposing of about 180 Seismic Group Recorders > (SGR-III) and associated geophone strings. > > RECORDERS > The SGR III is a single-channel, digital seismic recorder with a > theoretical dynamic range of 156 dB. Data are sampled at 500 samples > per second (or at 2 ms intervals) by a 12 bit A/D converter with gain > ranging from 0-90 dB in 6 dB steps, recorded on cartridge tape. > Total available recording time is about 30 minutes, with up to about > 100 programmable windows. The SGR's have been modified by the USGS > to turn on at preset times instead of using the standard radio turn > on. Timing is provided by a TXCO with an accuracy of 0.1 ppm (most > SGR clocks drift less than 20 milliseconds during a 24-hour period). > The SGR III recorders were designed by Amoco Production Company, > built by Globe Universal Sciences, Inc., and modified by the USGS. > IRIS-PASSCAL helped maintain the SGR system as a recording facility > available to PASSCAL users through the 1990s, and they were used very > successfully alongside the Refteks in many major controlled source > experiments. > Not all our recorders work - the facility was last used in 2001, and > the SGRs have been in storage ever since. We have available a > miscellaneous supply of spare boards, manuals, connectors, etc. > I estimate the cost to get each unit back in the field for a single > experiment would be >$50, and in a recent experiment in the western > USA I found it more cost-effective to pay for air-freight shipping of > Texan recorders from Europe, than to bring the SGR system out of its > current retirement. > > GEOPHONES > For each SGR III we also own a single string of 6 modified Mark > Products L-10B vertical-component geophones (8 Hz) connected in > series, with c. 1 m cable between each phone. > > We also own a large number of strings of 12 L-10B vertical phones, > and of 12 horizontal phones, in each case with c. 15 m cable between > each phone, one string per clip. > > > > I would consider offers to take all or any part of our equipment. > You would need to pay shipping. > Even if you are not interested, but know of anyone who would want > e.g. single geophones for teaching purposes, please forward this > message. > > > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Seismic recorders and geophones available - free to a good home From: Jim E ODonnell jimo17@........ Date: Mon, 21 Mar 2005 15:22:48 -0800 Hi Larry- I would be interesrted in any of the geophones that are available- would be glad to pay the shipping to NV...Jim Jim O'Donnell Geological/Geophysical Consultant GEOTECHNICAL APPLICATIONS 702.293.5664 geophysics@.......... 702.281.9081 cell jimo17@........ Jim ODonnell 661 Del Prado Dr. Boulder City, NV 89005 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>... On Mon, 21 Mar 2005 14:26:34 -0800 Larry Cochrane writes: > Hi Everyone, > > I received this email the other day. The geophones are not very > useful for earthquake > recording since they are 8 hz units. Since Stanford is near by I > could pick up and > ship some units to people who are interested in having one of the > records and/or > sensors. I have no idea how big the records are so I have no idea > what the shipping > costs would be. > > Regards, > Larry Cochrane > Redwood City, PSN > > Simon Klemperer wrote: > > Gray Jensen (USGS) suggested that you might have an interest, or > know > > of someone who might have an interest, in industry geophones. > > Simon Klemperer > > > > > > Subject: Seismic recorders and geophones available - free to a > good home > > > > Stanford University is disposing of about 180 Seismic Group > Recorders > > (SGR-III) and associated geophone strings. > > > > RECORDERS > > The SGR III is a single-channel, digital seismic recorder with a > > theoretical dynamic range of 156 dB. Data are sampled at 500 > samples > > per second (or at 2 ms intervals) by a 12 bit A/D converter with > gain > > ranging from 0-90 dB in 6 dB steps, recorded on cartridge tape. > > Total available recording time is about 30 minutes, with up to > about > > 100 programmable windows. The SGR's have been modified by the > USGS > > to turn on at preset times instead of using the standard radio > turn > > on. Timing is provided by a TXCO with an accuracy of 0.1 ppm (most > > > SGR clocks drift less than 20 milliseconds during a 24-hour > period). > > The SGR III recorders were designed by Amoco Production Company, > > built by Globe Universal Sciences, Inc., and modified by the USGS. > > > IRIS-PASSCAL helped maintain the SGR system as a recording > facility > > available to PASSCAL users through the 1990s, and they were used > very > > successfully alongside the Refteks in many major controlled source > > > experiments. > > Not all our recorders work - the facility was last used in 2001, > and > > the SGRs have been in storage ever since. We have available a > > miscellaneous supply of spare boards, manuals, connectors, etc. > > I estimate the cost to get each unit back in the field for a > single > > experiment would be >$50, and in a recent experiment in the > western > > USA I found it more cost-effective to pay for air-freight shipping > of > > Texan recorders from Europe, than to bring the SGR system out of > its > > current retirement. > > > > GEOPHONES > > For each SGR III we also own a single string of 6 modified Mark > > Products L-10B vertical-component geophones (8 Hz) connected in > > series, with c. 1 m cable between each phone. > > > > We also own a large number of strings of 12 L-10B vertical phones, > > > and of 12 horizontal phones, in each case with c. 15 m cable > between > > each phone, one string per clip. > > > > > > > > I would consider offers to take all or any part of our equipment. > > > You would need to pay shipping. > > Even if you are not interested, but know of anyone who would want > > > e.g. single geophones for teaching purposes, please forward this > > 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. > >
Hi Larry-  I would be interesrted in any of the geophones that = are=20 available-  would be glad to pay the shipping to NV...Jim

        &= nbsp;           &= nbsp;=20 Jim O'Donnell    =20

        = ;=20 Geological/Geophysical Consultant

        = ; =20 GEOTECHNICAL APPLICATIONS

702.293.5664        =   =20     geophysics@..........

702.281.9081 cell        = ;=20 jimo17@........

 

Jim=20 ODonnell

661=20 Del Prado Dr.

Boulder City, NV 89005

>>>>>>>>>>>>&= gt;>>>>>>>>>>>>>>>>>>= >>>>>>>>>>>>>>>>>>>= ;>>>>>>>>>>>>>...

 

On Mon, 21 Mar 2005 14:26:34 -0800 Larry Cochrane <lcochrane@..............>=20 writes:
> Hi Everyone,
>
> I received this email the = other=20 day. The geophones are not very
> useful for earthquake
>=20 recording since they are 8 hz units. Since Stanford is near by I
> = could=20 pick up and
> ship some units to people who are interested in having= one=20 of the
> records and/or
> sensors. I have no idea how big the= =20 records are so I have no idea
> what the shipping
> costs = would=20 be.
>
> Regards,
> Larry Cochrane
> Redwood City,= =20 PSN
>
> Simon Klemperer wrote:
> > Gray Jensen (USGS)= =20 suggested that you might have an interest, or
> know
> > = of=20 someone who might have an interest, in  industry geophones.
> &= gt;=20 Simon Klemperer
> >
> >
> > Subject: Seismic=20 recorders and geophones available - free to a
> good home
> &= gt;=20
> > Stanford University is disposing of about 180 Seismic Group=20
> Recorders
> > (SGR-III) and associated geophone=20 strings.
> >
> > RECORDERS
> > The SGR III is a= =20 single-channel, digital seismic recorder with a
> > theoretical=20 dynamic range of 156 dB. Data are sampled at 500
> samples
> = >=20 per second (or at 2 ms intervals) by a 12 bit A/D converter with
> = gain=20
> > ranging from 0-90 dB in 6 dB steps, recorded on cartridge = tape.=20
> > Total available recording time is about 30 minutes, with up = to=20
> about
> > 100 programmable windows.  The SGR's have= been=20 modified by the
> USGS
> > to turn on at preset times = instead=20 of using the  standard radio
> turn
> > on. Timing is= =20 provided by a TXCO with an accuracy of 0.1 ppm (most
>
> >= SGR=20 clocks drift less than 20 milliseconds during a 24-hour
> period).=20
> > The SGR III recorders were designed by Amoco Production = Company,=20
> > built by Globe Universal Sciences, Inc., and modified by the = USGS.=20
>
> > IRIS-PASSCAL helped maintain the SGR system as a=20 recording
> facility
> > available to PASSCAL users = through the=20 1990s, and they were used
> very
> > successfully = alongside the=20 Refteks in many major controlled source
>
> >=20 experiments.
> > Not all our recorders work - the facility was = last=20 used in 2001,
> and
> > the SGRs have been in storage ever= =20 since. We have available a
> > miscellaneous supply of spare = boards,=20 manuals, connectors, etc.
> > I estimate the cost to get each unit= back=20 in the field for a
> single
> > experiment would be >$= 50,=20 and in a recent experiment in the
> western
> > USA I = found it=20 more cost-effective to pay for air-freight shipping
> of
> &= gt;=20 Texan recorders from Europe, than to bring the SGR system out of
> = its=20
> > current retirement.
> >
> > GEOPHONES
= >=20 > For each SGR III we also own a single string of 6 modified Mark
&= gt;=20 > Products L-10B vertical-component geophones (8 Hz) connected in
&= gt;=20 > series, with c. 1 m cable between each phone.
> >
> &= gt; We=20 also own a large number of strings of 12 L-10B vertical phones,
>=20
> > and of 12 horizontal phones, in each case with c. 15 m cable= =20
> between
> > each phone, one string per clip.
> >= ;=20
> >
> >
> > I would consider offers to take = all or=20 any part of our equipment.
>
> > You would need to pay=20 shipping.
> > Even if you are not interested, but know of anyone = who=20 would want
>
> > e.g. single geophones for teaching = purposes,=20 please forward this
> > message.
> >
> >
&= gt;=20 >
> >
> >
> >
>
>=20 __________________________________________________________
>
>= =20 Public Seismic Network Mailing List (PSN-L)
>
> To leave this = list=20 email PSN-L-REQUEST@.............. with=20
> the body of the message (first line only): unsubscribe
> See= http://www.seismicnet.com/= maillist.html=20 for more information.
>
>
 
Subject: RE: Seismic recorders and geophones available - free to a good home From: "Steve Hammond" shammon1@............. Date: Mon, 21 Mar 2005 21:00:44 -0800 Larry, I would like some and maybe we can get some for Los Altos High School. Thanks, Steve Hammond -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of Jim E ODonnell Sent: Monday, March 21, 2005 3:23 PM To: psn-l@.............. Subject: Re: Seismic recorders and geophones available - free to a good home Hi Larry- I would be interesrted in any of the geophones that are available- would be glad to pay the shipping to NV...Jim Jim O'Donnell Geological/Geophysical Consultant GEOTECHNICAL APPLICATIONS 702.293.5664 geophysics@.......... 702.281.9081 cell jimo17@........ Jim ODonnell 661 Del Prado Dr. Boulder City, NV 89005 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>... On Mon, 21 Mar 2005 14:26:34 -0800 Larry Cochrane writes: > Hi Everyone, > > I received this email the other day. The geophones are not very > useful for earthquake > recording since they are 8 hz units. Since Stanford is near by I > could pick up and > ship some units to people who are interested in having one of the > records and/or > sensors. I have no idea how big the records are so I have no idea > what the shipping > costs would be. > > Regards, > Larry Cochrane > Redwood City, PSN > > Simon Klemperer wrote: > > Gray Jensen (USGS) suggested that you might have an interest, or > know > > of someone who might have an interest, in industry geophones. > > Simon Klemperer > > > > > > Subject: Seismic recorders and geophones available - free to a > good home > > > > Stanford University is disposing of about 180 Seismic Group > Recorders > > (SGR-III) and associated geophone strings. > > > > RECORDERS > > The SGR III is a single-channel, digital seismic recorder with a > > theoretical dynamic range of 156 dB. Data are sampled at 500 > samples > > per second (or at 2 ms intervals) by a 12 bit A/D converter with > gain > > ranging from 0-90 dB in 6 dB steps, recorded on cartridge tape. > > Total available recording time is about 30 minutes, with up to > about > > 100 programmable windows. The SGR's have been modified by the > USGS > > to turn on at preset times instead of using the standard radio > turn > > on. Timing is provided by a TXCO with an accuracy of 0.1 ppm (most > > > SGR clocks drift less than 20 milliseconds during a 24-hour > period). > > The SGR III recorders were designed by Amoco Production Company, > > built by Globe Universal Sciences, Inc., and modified by the USGS. > > > IRIS-PASSCAL helped maintain the SGR system as a recording > facility > > available to PASSCAL users through the 1990s, and they were used > very > > successfully alongside the Refteks in many major controlled source > > > experiments. > > Not all our recorders work - the facility was last used in 2001, > and > > the SGRs have been in storage ever since. We have available a > > miscellaneous supply of spare boards, manuals, connectors, etc. > > I estimate the cost to get each unit back in the field for a > single > > experiment would be >$50, and in a recent experiment in the > western > > USA I found it more cost-effective to pay for air-freight shipping > of > > Texan recorders from Europe, than to bring the SGR system out of > its > > current retirement. > > > > GEOPHONES > > For each SGR III we also own a single string of 6 modified Mark > > Products L-10B vertical-component geophones (8 Hz) connected in > > series, with c. 1 m cable between each phone. > > > > We also own a large number of strings of 12 L-10B vertical phones, > > > and of 12 horizontal phones, in each case with c. 15 m cable > between > > each phone, one string per clip. > > > > > > > > I would consider offers to take all or any part of our equipment. > > > You would need to pay shipping. > > Even if you are not interested, but know of anyone who would want > > > e.g. single geophones for teaching purposes, please forward this > > 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. > >
Larry,=20 I would like some and maybe we can get some for Los Altos High=20 School.
Thanks, Steve Hammond
-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of Jim E=20 ODonnell
Sent: Monday, March 21, 2005 3:23 PM
To:=20 psn-l@..............
Subject: Re: Seismic recorders and = geophones=20 available - free to a good home

Hi Larry-  I would be interesrted in any of the geophones = that are=20 available-  would be glad to pay the shipping to NV...Jim

           &= nbsp;         =20 Jim O'Donnell    =20

        =20 Geological/Geophysical Consultant

         =20 GEOTECHNICAL APPLICATIONS

702.293.5664          =20     geophysics@..........=

702.281.9081 cell        =20 jimo17@........

 

Jim ODonnell

661 Del Prado Dr.

Boulder City, NV 89005

>>>>>>>>>>>>>>>>>= ;>>>>>>>>>>>>>>>>>>= >>>>>>>>>>>>>>>>>>&= gt;>>>>>>>>>...

 

On Mon, 21 Mar 2005 14:26:34 -0800 Larry Cochrane <lcochrane@..............>= =20 writes:
> Hi Everyone,
>
> I received this email = the other=20 day. The geophones are not very
> useful for earthquake =
>=20 recording since they are 8 hz units. Since Stanford is near by I =
>=20 could pick up and
> ship some units to people who are = interested in=20 having one of the
> records and/or
> sensors. I have no = idea how=20 big the records are so I have no idea
> what the shipping =
>=20 costs would be.
>
> Regards,
> Larry = Cochrane
>=20 Redwood City, PSN
>
> Simon Klemperer wrote:
> > = Gray=20 Jensen (USGS) suggested that you might have an interest, or
> = know=20
> > of someone who might have an interest, in  industry = geophones.
> > Simon Klemperer
> >
> > =
>=20 > Subject: Seismic recorders and geophones available - free to a =
>=20 good home
> >
> > Stanford University is disposing = of about=20 180 Seismic Group
> Recorders
> > (SGR-III) and = associated=20 geophone strings.
> >
> > RECORDERS
> > = The SGR=20 III is a single-channel, digital seismic recorder with a
> > = theoretical dynamic range of 156 dB. Data are sampled at 500
> = samples=20
> > per second (or at 2 ms intervals) by a 12 bit A/D = converter with=20
> gain
> > ranging from 0-90 dB in 6 dB steps, = recorded on=20 cartridge tape.
> > Total available recording time is about = 30=20 minutes, with up to
> about
> > 100 programmable=20 windows.  The SGR's have been modified by the
> USGS =
> >=20 to turn on at preset times instead of using the  standard radio =
>=20 turn
> > on. Timing is provided by a TXCO with an accuracy = of 0.1=20 ppm (most
>
> > SGR clocks drift less than 20 = milliseconds=20 during a 24-hour
> period).
> > The SGR III recorders = were=20 designed by Amoco Production Company,
> > built by Globe = Universal=20 Sciences, Inc., and modified by the USGS.
>
> > = IRIS-PASSCAL=20 helped maintain the SGR system as a recording
> facility =
> >=20 available to PASSCAL users through the 1990s, and they were used =
> very=20
> > successfully alongside the Refteks in many major = controlled=20 source
>
> > experiments.
> > Not all our = recorders=20 work - the facility was last used in 2001,
> and
> > = the SGRs=20 have been in storage ever since. We have available a
> >=20 miscellaneous supply of spare boards, manuals, connectors, = etc.
> > I=20 estimate the cost to get each unit back in the field for a
> = single=20
> > experiment would be >$50, and in a recent experiment = in the=20
> western
> > USA I found it more cost-effective to = pay for=20 air-freight shipping
> of
> > Texan recorders from = Europe,=20 than to bring the SGR system out of
> its
> > current = retirement.
> >
> > GEOPHONES
> > For = each SGR=20 III we also own a single string of 6 modified Mark
> > = Products=20 L-10B vertical-component geophones (8 Hz) connected in
> > = series,=20 with c. 1 m cable between each phone.
> >
> > We = also own a=20 large number of strings of 12 L-10B vertical phones,
>
> = >=20 and of 12 horizontal phones, in each case with c. 15 m cable
> = between=20
> > each phone, one string per clip.
> >
> = >=20
> >
> > I would consider offers to take all or any = part of=20 our equipment.
>
> > You would need to pay = shipping.
>=20 > Even if you are not interested, but know of anyone who would want =
>
> > e.g. single geophones for teaching purposes, = please=20 forward this
> > message.
> >
> > =
> >=20
> >
> >
> >
>
>=20 __________________________________________________________
> =
>=20 Public Seismic Network Mailing List (PSN-L)
>
> To leave = this=20 list email PSN-L-REQUEST@............... =20 with
> the body of the message (first line only): = unsubscribe
>=20 See http://www.seismicnet.co= m/maillist.html=20 for more information.
>
>
 
Subject: RE: Seismic recorders and geophones available - free to a good home From: "Timothy Carpenter" GeoDynamics@....... Date: Tue, 22 Mar 2005 00:44:45 -0500 Larry, I would be very interested in acquiring three of the 12-component = strings -- one vertical and two horizontal. snip > > We also own a large number of strings of 12 L-10B vertical phones,=20 > and of 12 horizontal phones, in each case with c. 15 m cable between=20 > each phone, one string per clip. snip < Regards, -Tim- Timothy Carpenter 5043 Whitlow Ct. Commerce Twp., Mi 48382 248-363-4529 (voice & fax) 248-766-1629 (cell) geodynamics@........... (primary) geodynamics@....... (secondary) =A0 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Larry Cochrane Sent: Monday, March 21, 2005 5:27 PM To: psn-l@.............. Subject: Re: Seismic recorders and geophones available - free to a good = home Hi Everyone, I received this email the other day. The geophones are not very useful = for earthquake=20 recording since they are 8 hz units. Since Stanford is near by I could = pick up and=20 ship some units to people who are interested in having one of the = records and/or=20 sensors. I have no idea how big the records are so I have no idea what = the shipping=20 costs would be. Regards, Larry Cochrane Redwood City, PSN Simon Klemperer wrote: > Gray Jensen (USGS) suggested that you might have an interest, or know=20 > of someone who might have an interest, in industry geophones. > Simon Klemperer >=20 >=20 > Subject: Seismic recorders and geophones available - free to a good = home >=20 > Stanford University is disposing of about 180 Seismic Group Recorders=20 > (SGR-III) and associated geophone strings. >=20 > RECORDERS > The SGR III is a single-channel, digital seismic recorder with a=20 > theoretical dynamic range of 156 dB. Data are sampled at 500 samples=20 > per second (or at 2 ms intervals) by a 12 bit A/D converter with gain=20 > ranging from 0-90 dB in 6 dB steps, recorded on cartridge tape.=20 > Total available recording time is about 30 minutes, with up to about=20 > 100 programmable windows. The SGR's have been modified by the USGS=20 > to turn on at preset times instead of using the standard radio turn=20 > on. Timing is provided by a TXCO with an accuracy of 0.1 ppm (most=20 > SGR clocks drift less than 20 milliseconds during a 24-hour period).=20 > The SGR III recorders were designed by Amoco Production Company,=20 > built by Globe Universal Sciences, Inc., and modified by the USGS.=20 > IRIS-PASSCAL helped maintain the SGR system as a recording facility=20 > available to PASSCAL users through the 1990s, and they were used very=20 > successfully alongside the Refteks in many major controlled source=20 > experiments. > Not all our recorders work - the facility was last used in 2001, and=20 > the SGRs have been in storage ever since. We have available a=20 > miscellaneous supply of spare boards, manuals, connectors, etc. > I estimate the cost to get each unit back in the field for a single=20 > experiment would be >$50, and in a recent experiment in the western=20 > USA I found it more cost-effective to pay for air-freight shipping of=20 > Texan recorders from Europe, than to bring the SGR system out of its=20 > current retirement.=20 >=20 > GEOPHONES > For each SGR III we also own a single string of 6 modified Mark=20 > Products L-10B vertical-component geophones (8 Hz) connected in=20 > series, with c. 1 m cable between each phone. >=20 > We also own a large number of strings of 12 L-10B vertical phones,=20 > and of 12 horizontal phones, in each case with c. 15 m cable between=20 > each phone, one string per clip. >=20 >=20 >=20 > I would consider offers to take all or any part of our equipment.=20 > You would need to pay shipping. > Even if you are not interested, but know of anyone who would want=20 > e.g. single geophones for teaching purposes, please forward this=20 > message. >=20 >=20 >=20 >=20 >=20 >=20 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Seismic recorders and geophones available - free to a good home From: Bob Hancock Bob.Hancock@............ Date: Mon, 21 Mar 2005 23:07:28 -0700 Larry - I would be interested in one recording unit and one string of vertical geophones. Thanks Bob Hancock -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Larry Cochrane Sent: Monday, March 21, 2005 15:27 To: psn-l@.............. Subject: Re: Seismic recorders and geophones available - free to a good home Hi Everyone, I received this email the other day. The geophones are not very useful for earthquake recording since they are 8 hz units. Since Stanford is near by I could pick up and ship some units to people who are interested in having one of the records and/or sensors. I have no idea how big the records are so I have no idea what the shipping costs would be. Regards, Larry Cochrane Redwood City, PSN Simon Klemperer wrote: > Gray Jensen (USGS) suggested that you might have an interest, or know > of someone who might have an interest, in industry geophones. > Simon Klemperer > > > Subject: Seismic recorders and geophones available - free to a good home > > Stanford University is disposing of about 180 Seismic Group Recorders > (SGR-III) and associated geophone strings. > > RECORDERS > The SGR III is a single-channel, digital seismic recorder with a > theoretical dynamic range of 156 dB. Data are sampled at 500 samples > per second (or at 2 ms intervals) by a 12 bit A/D converter with gain > ranging from 0-90 dB in 6 dB steps, recorded on cartridge tape. > Total available recording time is about 30 minutes, with up to about > 100 programmable windows. The SGR's have been modified by the USGS > to turn on at preset times instead of using the standard radio turn > on. Timing is provided by a TXCO with an accuracy of 0.1 ppm (most > SGR clocks drift less than 20 milliseconds during a 24-hour period). > The SGR III recorders were designed by Amoco Production Company, > built by Globe Universal Sciences, Inc., and modified by the USGS. > IRIS-PASSCAL helped maintain the SGR system as a recording facility > available to PASSCAL users through the 1990s, and they were used very > successfully alongside the Refteks in many major controlled source > experiments. > Not all our recorders work - the facility was last used in 2001, and > the SGRs have been in storage ever since. We have available a > miscellaneous supply of spare boards, manuals, connectors, etc. > I estimate the cost to get each unit back in the field for a single > experiment would be >$50, and in a recent experiment in the western > USA I found it more cost-effective to pay for air-freight shipping of > Texan recorders from Europe, than to bring the SGR system out of its > current retirement. > > GEOPHONES > For each SGR III we also own a single string of 6 modified Mark > Products L-10B vertical-component geophones (8 Hz) connected in > series, with c. 1 m cable between each phone. > > We also own a large number of strings of 12 L-10B vertical phones, > and of 12 horizontal phones, in each case with c. 15 m cable between > each phone, one string per clip. > > > > I would consider offers to take all or any part of our equipment. > You would need to pay shipping. > Even if you are not interested, but know of anyone who would want > e.g. single geophones for teaching purposes, please forward this > message. > > > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Homebrew AS-1 seismometer From: "Dewayne Hill" n0ssy@........... Date: Sun, 27 Mar 2005 19:49:52 -0700 I just completed a homebrew AS-1 seismometer. I must say the most challenging part was trying to find a boom support = spring. Having no engineering degree so I was left to do the trail and error = method. I got very lucky. I just had a new LOWES lumber/hardware store = open very close to me. Being a new store their stock was full and complete. I found a spring = manufactured by Century Spring Corp. The part number on the package is "C-219". I purchased two of these = springs.=20 I had to do some resizing of these springs. The spring is 4.5" long. I = cut about 3/8" off of each coil. I then spread the coils of each spring = just far enough apart to mesh them together (about a 1/2" overlap.) I happened to have a 1/2" i.d. x 1" = spacer in my junk bin so I slid the spacer over the meshed coils so they = will not separate. I ordered a coil and magnet for Larry. The amplifier is from the = following URL http://users.viawest.net/~aloomis/seismom.htm a power = supply for this amplifier=20 can be found at http://users.viawest.net/~aloomis/seisprea.htm . When I started this project I requested a catalog from Century Spring. I = can not find a spring with a C-219 part number, but there is a spring = with the part number of 302 that is a very close match. Another spring that could be = tried is the 119. This one would have to be cut to the desired length. = Century Spring has a minimum order of $30. I must say that the sensitivity appears to be superb as compared to my = Lehman (but it's never been quite right after I rebuilt it.) All of the mechanical bits were purchased from LOWES. If you would like more information please contact me at = n0ssy@........... and not through the PSN list server. Dewayne Hill=20 Westminster, Co.
I just completed a homebrew AS-1=20 seismometer.
 
I must say the most challenging part = was trying to=20 find a boom support spring.
 
Having no engineering degree so I was = left to do=20 the trail and error method. I got very lucky. I just had a new LOWES=20 lumber/hardware store open very close to me.
 
Being a new store their stock was full = and=20 complete. I found a spring manufactured by Century Spring = Corp.
The part number on the package is "C-219". I purchased two of these = springs.
 
I had to do some resizing of these = springs. The=20 spring is 4.5" long. I cut about 3/8" off of each coil. I then spread = the coils=20 of each spring just far enough apart to mesh them
together (about a 1/2" overlap.)  I happened to have a 1/2" = i.d. x 1"=20 spacer in my junk bin so I slid the spacer over the meshed coils so they = will=20 not separate.
 
I ordered a coil and magnet for Larry. = The=20 amplifier is from the following URL http://users.viawe= st.net/~aloomis/seismom.htm=20 a power supply for this amplifier
can be found at http://users.viaw= est.net/~aloomis/seisprea.htm=20 ..
 
When I started this project I requested = a catalog=20 from Century Spring. I can not find a spring with a C-219 part number, = but there=20 is a spring with the part
number of 302 that is a very close match. Another spring that could = be=20 tried is the 119. This one would have to be cut to the desired length. = Century=20 Spring has
a minimum order of $30.
 
I must say that the sensitivity appears = to be=20 superb as compared to my Lehman (but it's never been quite right after I = rebuilt=20 it.)
 
All of the mechanical bits were = purchased from=20 LOWES.
 
If you would like more information = please contact=20 me at n0ssy@........... = and not=20 through the PSN list server.
 
 
 
Dewayne Hill
Westminster,=20 Co.
Subject: Re: Homebrew AS-1 seismometer From: John or Jan Lahr JohnJan@........ Date: Sun, 27 Mar 2005 21:17:20 -0700 Dewayne,

Good job of finding a spring!  Do you have some photos of your unit?  I think it would be good
to post some, along with your spring details, on my web site.  Are you using AmaSeis?  If so,
it would be interesting to save a 24-hour screen image of the next good sized event.  We could
compare it to one of the local AS1 posted here:
http://jclahr.com/science/psn/as1/heli/allas1.php

Cheers,
John

At 07:49 PM 3/27/2005, you wrote:
I just completed a homebrew AS-1 seismometer.
 
I must say the most challenging part was trying to find a boom support spring.
 
Having no engineering degree so I was left to do the trail and error method. I got very lucky. I just had a new LOWES lumber/hardware store open very close to me.
 
Being a new store their stock was full and complete. I found a spring manufactured by Century Spring Corp.
The part number on the package is "C-219". I purchased two of these springs.
 
I had to do some resizing of these springs. The spring is 4.5" long. I cut about 3/8" off of each coil. I then spread the coils of each spring just far enough apart to mesh them
together (about a 1/2" overlap.)  I happened to have a 1/2" i.d. x 1" spacer in my junk bin so I slid the spacer over the meshed coils so they will not separate.
 
I ordered a coil and magnet for Larry. The amplifier is from the following URL http://users.viawest.net/~aloomis/seismom.htm a power supply for this amplifier
can be found at http://users.viawest.net/~aloomis/seisprea.htm .
 
When I started this project I requested a catalog from Century Spring. I can not find a spring with a C-219 part number, but there is a spring with the part
number of 302 that is a very close match. Another spring that could be tried is the 119. This one would have to be cut to the desired length. Century Spring has
a minimum order of $30.
 
I must say that the sensitivity appears to be superb as compared to my Lehman (but it's never been quite right after I rebuilt it.)
 
All of the mechanical bits were purchased from LOWES.
 
If you would like more information please contact me at n0ssy@........... and not through the PSN list server.
 
 
 
Dewayne Hill
Westminster, Co.
Subject: Poster of February 10, 2005, Arkansas earthquake From: John or Jan Lahr JohnJan@........ Date: Sun, 27 Mar 2005 21:29:20 -0700 http://www.ceri.memphis.edu/usgs/products/download/posters/ArkansasPoster.pdf This is a poster from the USGS with lots of information on this and previous events in the New Madrid seismic zone. Cheers, John __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: event registered From: "RANDY KIMBALL" randy.kimball@........... Date: Mon, 28 Mar 2005 22:44:57 -0600 Guys, I have an event charted at about 17:28 UTC from here in Keller, = Texas. This is after the 8.7 in Indonesia, after the 6.0 in the same = zone, but before the next 5.3 listed in the same general area. I = haven't found an event listed for that time span. Does anyone else have = an event to link with my data? My GPS is 32.93N -97.213W 232 Elev. This event charts out about the same mag here as the 8.7 did. The event charts from 17:27 through 17:49, ..... something happened. .. any others with matching data in the local area??? -randy-
Guys, I have an event charted = at about 17:28=20 UTC from here in Keller, Texas.  This is after the 8.7 in = Indonesia, after=20 the 6.0 in the same zone, but before the next 5.3 listed in the=20 same general area.  I haven't found an event listed for that = time=20 span.  Does anyone else have an event to link with my = data?
 
My GPS is 32.93N  = -97.213W   =20 232 Elev.
 
This event charts out about the same = mag here as=20 the 8.7 did.
 
The event charts = from 17:27 through=20 17:49, ..... something happened.
 
  .. any others with matching data = in the=20 local area???
 
-randy-
Subject: bbrequest From: Dave Nelson davenn@............... Date: Tue, 29 Mar 2005 21:37:06 +1000 hi Larry the bbrequest doesnt seem to be working lately havent been able to d/l any seismograms from any of the stations has anyone else had problems with it ? cheers Dave __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Homebrew AS-1 seismometer From: Jack Ivey ivey@.......... Date: Tue, 29 Mar 2005 09:11:01 -0500 Dewayne, What period were you able to get from your vertical? Jack __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Mb question From: Stephen & Kathy skmort@.......... Date: Tue, 29 Mar 2005 11:37:39 -0800 mornin, I've been trying to find a table or chart or formula which will yield the Q(Delta,h), distance and depth values which I can use to plug into the Mb magnitude formula!! Thanks in advance for any help in finding it!!! Stephen PSN Station #55 near Pilot Hill Ca. USA 38.828N 120.979W __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: bbrequest From: Larry Cochrane lcochrane@.............. Date: Tue, 29 Mar 2005 18:07:36 -0800 Hi Dave, I restarted the program that receives the sensor data over the Internet. That seems to have fixed the problem. Larry Cochrane Redwood City, PSN Dave Nelson wrote: > hi Larry > the bbrequest doesnt seem to be working lately > > havent been able to d/l any seismograms from any of the stations > > has anyone else had problems with it ? > > cheers > Dave __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Mb question From: Larry Cochrane lcochrane@.............. Date: Tue, 29 Mar 2005 18:39:09 -0800 Stephen, WinQuake uses the following formula to calculate mb magnitude mb = log10(A/T) + 0.01*D + 5.9 A = Peak P wave displacement amplitude in micrometers, T = Period of the displacement amplitude and D = Distance in degrees See http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag3.pdf for more information. Regards, Larry Cochrane Redwood City, PSN Stephen & Kathy wrote: > mornin, I've been trying to find a table or chart or formula which > will yield the Q(Delta,h), distance and depth values which I can use to > plug into the Mb magnitude formula!! Thanks in advance for any help in > finding it!!! > Stephen > PSN Station #55 > near Pilot Hill Ca. USA > 38.828N 120.979W > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Mb question From: John or Jan Lahr JohnJan@........ Date: Tue, 29 Mar 2005 20:19:35 -0700 Hi Larry, That's true for shallow, regional events within about 600 km. For teleseismic events an emperical table is used. I've posted the table and Ray Buland's FORTRAN code, which is used by NEIC to compute mb. See: http://jclahr.com/science/software/mb/ Cheers, John At 07:39 PM 3/29/2005, you wrote: >Stephen, > >WinQuake uses the following formula to calculate mb magnitude > >mb = log10(A/T) + 0.01*D + 5.9 > >A = Peak P wave displacement amplitude in micrometers, T = Period of the >displacement amplitude and D = Distance in degrees > >See http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag3.pdf for more >information. > >Regards, >Larry Cochrane >Redwood City, PSN > >Stephen & Kathy wrote: >>mornin, I've been trying to find a table or chart or formula which >>will yield the Q(Delta,h), distance and depth values which I can use to >>plug into the Mb magnitude formula!! Thanks in advance for any help in >>finding it!!! >> Stephen >> PSN Station #55 >> near Pilot Hill Ca. USA >> 38.828N 120.979W >>__________________________________________________________ >>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 the body of the >message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Mb question: correction From: John or Jan Lahr JohnJan@........ Date: Tue, 29 Mar 2005 20:37:00 -0700 Hi Larry, I spoke too soon!!! You were correct. The formula you gave is an alternative to the more complex one for mb using a table. I've posted the table and Ray Buland's FORTRAN code, which is used by NEIC to compute mb. See: http://jclahr.com/science/software/mb/ Looking at: http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag3.pdf I see that, given: A is amplitude in microns D is distance in degrees T is period in seconds Larry Braile gives this formula for MS: MS = log10(A/T) + 1.66*log10(D) + 3.3 and this formula for mb: mb = log10(A/T) + 0.01*D + 5.9 Cheers, John At 07:39 PM 3/29/2005, you wrote: >Stephen, > >WinQuake uses the following formula to calculate mb magnitude > >mb = log10(A/T) + 0.01*D + 5.9 > >A = Peak P wave displacement amplitude in micrometers, T = Period of the >displacement amplitude and D = Distance in degrees > >See http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag3.pdf for more >information. > >Regards, >Larry Cochrane >Redwood City, PSN > >Stephen & Kathy wrote: >>mornin, I've been trying to find a table or chart or formula which >>will yield the Q(Delta,h), distance and depth values which I can use to >>plug into the Mb magnitude formula!! Thanks in advance for any help in >>finding it!!! >> Stephen >> PSN Station #55 >> near Pilot Hill Ca. USA >> 38.828N 120.979W >>__________________________________________________________ >>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 the body of the >message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Mb question From: Stephen & Kathy skmort@.......... Date: Tue, 29 Mar 2005 21:12:37 -0800 Thanks Larry,,, I did look at your help files on how winquake calculates Mb,, but it refers to a formula which requires the table,, so I assumed you had a file with the table, but couldn't find it,,, then I said, well I'll just let your program calculate Mb,, but for some reason it is not obvious to me how to do it???? That is when I went looking for a table to set up my own calculation!! Looking at Johns fortran info and table I realize it isn't as simple as I first thought it would be,,, a straight forward array, with depth on one side and distance on the other would be something on the order of 800 by 108!! The fortran table is 17 by 108! And as near as I can tell from the formulas, it isn't just bands of depth,,, it appears that the full range of Q is wider than the limits in the table??? Per chance and just for fun, has anyone converted it to a PC or dos program????? Or perhaps a mathcad program??? Thanks all,,, it is becoming a real education!!! Stephen 38.828N 120.979W Larry Cochrane wrote: > Stephen, > > WinQuake uses the following formula to calculate mb magnitude > > mb = log10(A/T) + 0.01*D + 5.9 > > A = Peak P wave displacement amplitude in micrometers, T = Period of the > displacement amplitude and D = Distance in degrees > > See http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag3.pdf for more > information. > > Regards, > Larry Cochrane > Redwood City, PSN > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Mb problem From: Stephen & Kathy skmort@.......... Date: Wed, 30 Mar 2005 12:57:59 -0800 Well,, I just figured out my winquake Mb problem,,, a simple upgrade should take care of it,, HA!!!! It would still be fun to play with and compare if we had a table version that would run under dos or windows,,, hint hint,, ha!!! Stephen 38.828N 120.979W __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Mb problem From: John or Jan Lahr JohnJan@........ Date: Thu, 31 Mar 2005 06:41:31 -0700 Stephen, I've updated the page on mb: http://jclahr.com/science/software/mb/ It now includes the source and compiled code for computing magnitude via the Q table used by NEIC as well as by the formula given by Larry Braile. There is a link to the graph by Gutenberg and Richter (1956) which is the basis for the Q table. Cheers, John At 01:57 PM 3/30/2005, you wrote: >Well,, I just figured out my winquake Mb problem,,, a simple upgrade >should take care of it,, HA!!!! > >It would still be fun to play with and compare if we had a table version >that would run under dos or windows,,, hint hint,, ha!!! > > Stephen > 38.828N 120.979W >__________________________________________________________ > >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. >Date: Tue, 29 Mar 2005 21:12:37 -0800 >From: Stephen & Kathy >User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.7.2) >Gecko/20040804 Netscape/7.2 (ax;nscd1) >X-Accept-Language: en-us, en >To: psn-l@.............. >Subject: Re: Mb question >Reply-To: psn-l@.............. >Sender: psn-l-request@.............. > >Thanks Larry,,, I did look at your help files on how winquake >calculates Mb,, but it refers to a formula which requires the table,, so >I assumed you had a file with the table, but couldn't find it,,, then I >said, well I'll just let your program calculate Mb,, but for some reason >it is not obvious to me how to do it???? That is when I went looking for >a table to set up my own calculation!! > >Looking at Johns fortran info and table I realize it isn't as simple as I >first thought it would be,,, a straight forward array, with depth on one >side and distance on the other would be something on the order of 800 by >108!! The fortran table is 17 by 108! And as near as I can tell from >the formulas, it isn't just bands of depth,,, it appears that the full >range of Q is wider than the limits in the table??? Per chance and just >for fun, has anyone converted it to a PC or dos program????? Or perhaps >a mathcad program??? > >Thanks all,,, it is becoming a real education!!! > > Stephen > 38.828N 120.979W Larry Cochrane wrote: >Stephen, >WinQuake uses the following formula to calculate mb magnitude >mb = log10(A/T) + 0.01*D + 5.9 >A = Peak P wave displacement amplitude in micrometers, T = Period of the >displacement amplitude and D = Distance in degrees >See http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag3.pdf for more >information. >Regards, >Larry Cochrane >Redwood City, PSN __________________________________________________________ Public Seismic Network Mailing List (PSN-L)