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Subject: Re: Caution on low pass filtering emphasis
From: RSparks rsparks@..........
Date: Fri, 01 Jan 2010 21:37:37 -0800

Hello Thomas,

I took a look before and after the quake but did not see anything unusual.  

Not unusual for this location is to have a fuzzy trace (~1 Hz High Pass) beginning about 0630 and ending about 1700 local times.  Since I am using a vertical, I have attributed this to the sun warming the atmosphere.  But, the noise does not seem to be present during non-work days which is completely inconsistent with a solar source.  I live about 2 miles from any serious auto traffic which would be on I-90 in Central Washington.  I have no explanation for this "fuzz"

The "fuzz" is not visible with either the all pass or low pass filters in place.

One puzzle here is that in the past I could get a fairly clean FFT peak at about 6 seconds and little at longer periods.  Lately, I notice a broader peak at 6 seconds and a second peak as low as 44 seconds (both very broad peaks).  I took a look at about 4 hours of data a few moments ago and confirmed what I had previously found.  Would we be seeing the same thing?  


Thomas Dick wrote:

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> | Message 4                                                           |
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> Subject: Re: Caution on  low pass filtering emphasis
> From:    Thomas Dick 
> Date:    Fri, 01 Jan 2010 10:38:55 -0600
> I did download your files...but that muddy the waters a little. My 
> interests here have turned to the microscisms at about  period 6 sec and 
> 35 sec. USIN (locally) and my own equipment have shown these 
> "irritating" noises more frequently this Fall than in the past. In fact 
> I pull down USIN's record and compared it to mine. Two hours before the 
> quake and about seven hours after the quake's arrival the "noise" was 
> still very prevalent. I don't see any sign of this "problem" on your 
> record. Could you comment; would this be a regional thing, electronics 
> or period of the seismic units involved?

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