PSN-L Email List Message

Subject: Re: Newbie questions...
From: Larry Cochrane cochrane@..............
Date: Thu, 08 Jun 2000 00:26:25 -0700

Hi Steve,

At 06:12 AM 6/7/00 +1000, Steve Olney  wrote:
>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.

Yes, I believe that is correct.

>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?

I like running horizontals, if the sensor is in an area like mine with a
lot of local ground noise from car trucks etc. Since most of the energy of
the noise is in the vertical direction, a horizontal sensor will not pick
up as much signal from cars and trucks going by. You can see the difference
by looking at my *.LCZ (vertical), *.LCN (N-S horizontal) and *.LCE (E-W)
event files. A good example is a M2.6 event 26km from me that happened last
month. The event files are 000530A.LCZ, 000530A.LCN and 000530A.LCE. As you
can see the event is hard to see in the vertical direction. The horizontal
channels show the event very clearly. The sensor used to record this event
is a three channel forced-balanced accelerometer with all channels having
the same sensitivity.

>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?

Thanks, but given the extra cost to transfer money don't worry about it. 

Larry Cochrane
Redwood City, PSN



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Larry Cochrane <cochrane@..............>