Goals for Fall 2002 Semester
Heiner Igel's Lectures on geophysics and Earth science: http://www.geophysik.uni-muenchen.de/~igel/
B. H. Suits, Michigan Technological University:
An advanced text by Erhard Wielandt
Latest version in MSWord Format
Earlier version in HTML
Wolfgang Lenhardt Lecture on
Public Seismic Network Mailing Lists and Archives: http://www.seismicnet.com/maillist.html
(Reading the PSN archives and joining this list is strongly recommended!)
Alan Jones' Web site with AmaSeis to display data from DATAQ DI-194RS AD: http://bingweb.binghamton.edu/~ajones/AmaSeis.html
Using a DATAQ DI-158U ADC with AmaSeis.
Bob McClure's Software
Randall Peters' FFT software page.
Ground motion amplitude and velocity as a function of distance, magnitude, and depth. (Only works well with MSIE -- Not Firefox.) Keep in mind that bacteria range from about 1 to 10 microns in diameter, while a human hair may be from 50 to 100 microns in diameter.
Graphs showing the distribution of "auto picks" from thousands of seismograms. These are helpful in determining which phases are most easily seen.
First the equations: http://hyperphysics.phy-astr.gsu.edu/hbase/oscda.html
Compare damped and undamped motion: http://www.kettering.edu/~drussell/Demos/SHO/damp.html
Velocity response of a geophone with various damping ratios:
A good applet from Wolfgang Bauer, Michigan State University, for damped harmonic motion: d.htm
He has posted this and many other applets for simple physical systems in his Applet Collection.
One can see a graph of the displacement from a damped harmonic oscillator on this page. The equations to keep in mind are (where mass = m, spring constant = k, and damping proportional to velocity = b):
Omega = (2Pi * frequency) = [sqrt(4mk - b**2)]/2m
The damping factor = b/ [2 sqrt(mk)]
If the damping factor is zero (b = 0) then omega = sqrt(k/m)
If the damping factor is 1 (b = 2 sqrt(mk) ) damping is critical and a displacement will return to zero exponentially.
If the damping factor is greater than 1, displacement will return to zero at a slower exponential rate.
A damping factor of 0.7 to 0.8 is good for seismic instruments. To see what 0.8 looks like, use the applet above and set m = k = 1 and b = 1.6. There is a very small overshoot and then a return essentially to zero. For 0.7, set m = k = 1 and b = 1.4.
Given the observed amplitude of two successive peaks, the damping ration can be computed on this page.
Amplifier/Filter circuit (amateur)
Peter Roberts' circuit to boost the low-frequency response of a velocity sensor.
Larry Cochrane's Amplifier/Circuit (professional)
Davis Saum has posted his electronics schematics and he sells assembled units and kits.
Swinging Gate Boom-Length Considerations
Zero-length spring for a long-period vertical.
Improving a geophone to produce an affordable, broadband seismometer. A Stanford University PhD thesis by Aaron Barzilai in pdf format (1.7 MB). These appear to be slides from a talk on his thesis.
Additional links to Aaron's geophone research at Stanford appear here: http://micromachine.stanford.edu/smssl/projects/Geophones/
Bob McClure's horizontal ( relatively small, but with strong magnets) and vertical designs.
Especially good description of swinging gate (Lehman) system: http://users.viawest.net/~aloomis/seismom.htm
Folded pendulum: http://jclahr.com/science/psn/folded/
Inverted pendulum: http://jclahr.com/science/psn/inverted/
Randall Peters' technique
Karl Cunningham's Home-made Force Balance Accelerometer
Diamagnetic Suspension Seismometers
Silicon Micromachined Accelerometer/Seismometer
Hall Effect Sensor
Chris Chapman's Design: http://mariottim.interfree.it/doc11_e.htm
Hall Effect, Diamagnetic, and other good ideas
Meredith Lamb's Pages: http://geocities.com/meredithlamb/
Sean-Thomas Morrissey's STM-8 design:
David Saum's Inexpensive Seismometer Project
Larry Cochran's Public Seismic Network Supplies
Mauro Mariotti's Solutions
http://www.infoeq.it or the mirror: http://mariottim.interfree.it/index_e.htm
Summary of Seismometers for Teaching and Research: http://quake.eas.gatech.edu/Instruments/InstrumentSurvey.htm
Demonstration Seismographs (Although these were designed to illustrate how a seismic sensor works they do provide a possible starting point for a working system.): http://quake.eas.gatech.edu/Instruments/LPVERT0.htm
ORFEUS web site with links to many sensors and approximate prices for many of them.
Guralp Broadband Force Feedback: http://www.guralp.net /
$25 DATAQ DI-194RS: http://dataq.com/194.htm
See this page for more information on the DATAQ AD's.
Randall Peters' Game Port AD: http://arxiv.org/html/physics/0202023
Sensors Magazine: http://www.sensorsmag.com/
Chip Center: http://www.chipcenter.com/
US Educational Seismograph Network (With links to most US networks): http://www.indiana.edu/~usesn/
Georgia Educational Seismograph Network (Tim Long): http://quake.eas.gatech.edu/teachnet/GaESNnetwork.htm
Italian Experimental Seismic Network Sites
Friuli Experimental Seismic Network