PSN-L Email List Message

Subject: Re: Instrument quality - microseisms
From: Thomas Dick dickthomas01@.............
Date: Thu, 22 Oct 2009 09:26:24 -0500

Barry Lotz wrote:
> To all
> Related to instrument quality- maybe. I have noticed a lot more 
> microseismic activity the last few days. The background noise on my 
> vertical is around +/- 300 counts @  8.7 sec  and 6.6 sec  (two narrow 
> peaks). I don't remember this magnitude in years past. I'm sure it is 
> weather related. I live about 200 miles east of the west coast of 
> northern California. Anyone else noticed an increase in background 
> lately? Every time I look at the output I think I'm looking at surface 
> waves after an event.
> Barry
 From about the 9th of October until yesterday, I was getting very 
strong peaks in the frequency range of .177Hz or period of 6 seconds 
here in southern Indiana. Today that peak as disappeared and a lesser 
peak exists at about .142 Hz or period of approximately 7 seconds.  It 
was so strong that I gave up posting earthquakes to the network because 
they just weren't clear without strong filtering. I, too, looked for a 
reason; Great Lakes, Gulf of Mexico and both the east and west coast. I 
could find no real association. I had NO local winds and no serious 
temperature changes.

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