PSN-L Email List Message

Subject: Re: L15B 4.5 Geophone, detecting teleseismic earthquake
From: ChrisAtUpw@.......
Date: Thu, 30 Mar 2006 21:57:46 EST


 
In a message dated 31/03/2006, jonfr500@......... writes:

Is it  impossible for L15B 4.5Hz geophone to detect teleseismic
earthquakes or  just improbable. 


Hi Jon,
 
    The sensitivity is down to ~1/5 at 2 Hz and it  falls off increasingly 
rapidly below this. At 1 Hz it is ~1/20. So what you can  see depends on the P 
wave frequency and on the magnitude of the quake. I  would say that it may be 
'difficult'. 
    It is possible to use a 'Roberts type' frequency  compensating amplifier 
to boost the output of a 4.5 Hz geophone fairly level  down to ~0.5 Hz. This 
enables you to use these geophones fairly well for  teleseismic quakes. 
 
    Regards,
 
    Chris Chapman





In a message dated 31/03/2006, jonfr500@......... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Is it=20 impossible for L15B 4.5Hz geophone to detect teleseismic
earthquakes or= =20 just improbable.
Hi Jon,
 
    The sensitivity is down to ~1/5 at 2 Hz and it=20 falls off increasingly rapidly below this. At 1 Hz it is ~1/20. So what you=20= can=20 see depends on the P wave frequency and on the magnitude of the quake.=20= I=20 would say that it may be 'difficult'. 
    It is possible to use a 'Roberts type' frequenc= y=20 compensating amplifier to boost the output of a 4.5 Hz geophone fairly level= =20 down to ~0.5 Hz. This enables you to use these geophones fairly well fo= r=20 teleseismic quakes.
 
    Regards,
 
    Chris Chapman

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