PSN-L Email List Message
Subject: Re: Timing Accuracy Within WinSDR
From: "Thomas Dick" dickthomas01@.............
Date: Mon, 14 Jul 2008 10:12:11 -0500
Since I raised the issue, I would like to put an end to it. I had several
checks made on my coordinates. That wasn't an issue. Then, using the largest
quake in the Illinois group in April, I acquired data from eight sites
besides my own. I used WinQuake and only the records of the vertical
instruments at each site. The sites ranged from 35 km to 173 km from the
epicenter; all to the east of the epicenter. The educationally sponsored
sites (using the tables in WinQuake) showed a variation of zero to 1.6
seconds deviation from the expected arrival of P. The other four which are
PP sites had an average deviation of 5.3 seconds. I excluded one site which
was off 77 seconds. So, my deviation of 3 seconds was better than average
in this group and allows the rest of the deviation to be blamed on things
like the bowl-shaped syncline that exists here and several known faults.
Most interesting to me was that the most accurate educational site (where P
arrived excatly as expected) was 90 km away from the epicenter and sits in a
cave of limestone approximately of the same type as that found at the focus.
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