PSN-L Email List Message

Subject: Re: L15B 4.5 Geophone, detecting teleseismic earthquake
From: Stephen & Kathy skmort@..........
Date: Fri, 31 Mar 2006 10:15:32 -0800


Count me in,,,   I'd like to see your circuit!!!!
   Stephen
   PSN Station #55

ChrisAtUpw@....... wrote:
> In a message dated 31/03/2006, system98765@............. writes:
> 
>     Hi Chris (& everyone else),
>     Where can one get more information about the 'Roberts Amplifier'?
>     Kareem
> 
> Hi Kareem,
>  
>     Go to http://psn.quake.net/bibliography.html 
>  
>     Roberts, PM "A Versatile Equilization Circuit for Increasing 
> Seismometer Velocity Response Below the Natural Frequency." (for 4.5Hz 
> geophones) BSSA,  vol 79, pp 1607-1617 Oct. 1989
>  
>     Your local library should be able to get you a photocopy.
>  
>     I made some simple circuit changes which reduced the very low 
> frequency noise, if anyone is interested. The modified circuit seems to 
> work fine. Lennartz use geophone compensators of this general type on 
> their professional range. You get about a factor of 10 reduction in the 
> minimum frequency - e.g. a 4.5Hz geophone will reproduce ~flat down to 
> 0.45Hz. This enables you to pick up teleseismic quakes as well as local 
> and regional ones.
>  
>     Regards,
>  
>     Chris Chapman
>  
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