Yesireee, The mass serves as a reference point
against which the earth moves. But only frequencies
at or above the point of resonance as I understand.
Below resonance the mass starts to move with the Earth
and more so as the frequency lowers. You must somehow
lower gravity accelerational effects to the point where you get a
4 second period before you can easily fit the
electronics to the sensor wuthout a lot of
equalization to get a flat response ove the range of interest.
Possibly 1 to 3ft/s^2 instead of 32ft/s^2 .
How you do this is the real trick for a spring and a mass.

:-) :-| :-O :-(

----- Original Message ----- 
From: 
To: 
Sent: Saturday, April 05, 2008 1:20 PM
Subject: Re: Whip antenna


> In a message dated 2008/04/05, tchannel1@............ writes:
> 
>> Hi Folks, If I had a 36" whip antenna, just a piece of spring steel rod, 
>> with a small mass on the tip, how much would the tip move during a earthquake?
> 
> Hi Ted,
> 
>       The mass should ideally NOT move at all ! It is the Earth which moves. 
> See the graphs at http://jclahr.com/science/psn/magnitude.html for actual 
> amplitides of phases.
> 
>       Regards,
> 
>       Chris Chapman   
>
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