PSN-L Email List Message

Subject: Newbie questions...
From: "Steve Olney" ollaneg@...........
Date: Wed, 7 Jun 2000 06:12:54 +1000

G'day All,
While hunting around for something else (can't remember what it was now) a
couple of days ago, I found the PSN websites etc.  I am interested in
experimenting with a home-made seismograph and found the information
available to be very useful.   However, I have a few questions:-

1. All the seismograms I have seen on the sites show the P wave as being
smaller than the S wave.  As I understand it the P wave is longitudinal and
the S wave is traverse, i.e. they are orthogonal.

Question: Wouldn't the relative amplitudes then depend on the orientation of
a horizontal seismograph (i.e. a Lehman)?   I think I can understand that a
vertical seismograph would show the higher S wave close to an event, but the
situation for a horizontal one has me puzzled.

2.  I would like to try and build a vertical seismograph using some Aura
shaker transducers I have.  I have tested the resonance frequency and they
appear to be around 40Hz.  I intend to try and make a vertical force-balance
type which I understand is really an accelerometer.

Question:  What is the relative sensitivities and relative amplitudes of
events of horizontal versus vertical seismographs?  What are the relative
pros and cons of vertical versus horizontal seismographs?   Is there any
disadvantage in using accelerometer (force-balance?) types versus
displacement or velocity types of seismographs?

3. If I wanted to send a contribution to the supporters of this email
reflector, who, where and how could I send it from here in Australia?

Best regards
Steve Olney  QF56IK : Lat -33 34 07, Long +150 44 40)
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Larry Cochrane <cochrane@..............>