PSN-L Email List Message

Subject: Re: My Kermadec Islands Region earthquake recording
From: ChrisAtUpw@.......
Date: Wed, 17 May 2006 05:53:52 EDT


In a message dated 17/05/06, jonfr500@......... writes:

>  did clean everything above 1Hz out of the recording to actually see
> the signal. I did the same thing with the eastern siberia earthquake in
> April, that I detected. Even if the response falls flat below 2Hz,
> there seems to be surprising lot of data below 2Hz.

Hi Jon,

       The geophone response will fall to 1/5 at 2Hz, to 1/20 at 1 Hz and to 
1/100 at 0.45 Hz. It does not 'fall flat', more like it takes a 'nose dive'!
       If you get strong enough seismic signals you will certainly see them 
to below 1 Hz. You may also see locally generated noise as the result of the 
quake.
       The geophone compensator circuits are designed to go from the 20 / 10 
Hz of the low pass filter down to 0.45 Hz, flat to velocity. You do get some 
additional noise, but it is quite small. This does enable you to detect 
teleseismic P and S waves with a 4.5 Hz geophone.

       Regards,

       Chris Chapman

In a message=20=
dated 17/05/06, jonfr500@......... writes:


I
did clean everything abov= e 1Hz out of the recording to actually see
the signal. I did the same thing with the eastern siberia earthquake in
April, that I detected. Even if the response falls flat below 2Hz,
there seems to be surprising lot of data below 2Hz.


Hi Jon,

      The geophone response will fall to=20= 1/5 at 2Hz, to 1/20 at 1 Hz and to 1/100 at 0.45 Hz. It does not 'fall flat'= , more like it takes a 'nose dive'!
      If you get strong enough seismic si= gnals you will certainly see them to below 1 Hz. You may also see locally ge= nerated noise as the result of the quake.
      The geophone compensator circuits a= re designed to go from the 20 / 10 Hz of the low pass filter down to 0.45 Hz= , flat to velocity. You do get some additional noise, but it is quite small.= This does enable you to detect teleseismic P and S waves with a 4.5 Hz geop= hone.

      Regards,

      Chris Chapman

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