PSN-L Email List Message
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?
Roger
Thomas Dick wrote:
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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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