PSN-L Email List Message

Subject: Equipment: SG vs. Lehman...Hybrid
From: Mark Andrews mja6042@.............
Date: Thu, 24 May 2001 22:51:28 -0500

Dear Everyone,

I still have a lot to learn so please forgive my ignorance.  

I know that teleseismic events generally dominate in the lower frequency
range.  Therefore a Lehman seismometer with its longer natural period seems
like it would be the instrument of choice for detecting teleseismic events.
 However, everything I read tells me the displacement sensor, which is
found on the bob of the Shackleford-Gundersen Seismometer can be built to
detect much weaker events than the velocity sensor found on the end of a

It seems like the thing to do then is build Lehman with a displacement
sensor similar to the one found on a Shackleford-Gundersen seismometer in
place of the magnet and coil on the boom of the Lehman.

I have not heard of anyone doing this.  Is there a reason?  Something I
have not taken into consideration?

I'm just curious because I'm looking to build my second instrument.  My
first is a Shackleford-Gundersen which I have been running since the end of
December.  I've picked up lots of quakes with it since then.  The only big
one I missed was the great quake in India due to my data logging computer
re-booting after a minor power blip.  (Just my luck!!!)  Now the computer
is on a UPS, go figure.

Thanks for any info anyone may have.

Mark Andrews
Texas A&M Class of '02 (Gig 'em)


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