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. 
Enough said! 


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