PSN-L Email List Message

Subject: Re: Range of 4,5Hz geophone
From: John or Jan Lahr JohnJan@........
Date: Sun, 08 Jan 2006 08:32:57 -0800

Hi Ian,

It's possible that the small event was triggered by the arriving 
seismic waves, although this usually occurs later when the surface 
waves are arriving.  See, for example, this page by USGS seismologist 
Andy Michael:
This has been observed in may volcanic and hydrothermal areas, where 
presumable there are some "spots" that are so close to failure that 
the added strain produced by the waves of a distant earthquake can 
set some of them off.

Andy's main page is:

This "event" is more likely just the high frequency component of the 
P wave.  It's hard to tell from the seismograms, but if it starts at 
exactly the same time as P on the Lehman, then it's probably not a 
triggered event.


At 04:40 AM 1/8/2006, you wrote:
>I'm getting an amazing trace on my Lehman of the Greek quake, still 
>in progress.  Interestingly, there is a small event on my geophone 
>which seems to co-incide with the P wave.  Is this likely?  See 
>I'm just about to fit a permanent set of heaters in the box.  The 
>temporary desk lamp has been great since I put it in, cured the 
>problem completely.  I'll have to wait a bit now so as to not 
>disturb the trace in progress....
>Ian Smith


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