PSN-L Email List Message

Subject: Re: Clock drift ?
From: Larry Cochrane lcochrane@..............
Date: Mon, 29 Jan 2007 01:57:57 -0800

Hi Jón,

It may not be a timing problem. Since your event file shows that the A/D board was 
locked to GPS time, I ready don't think your timing could be off by around 10 seconds.

You need the following for WinQuake to place the P and S markers correctly. Correct 
station timing and latitude and longitude information, and for the event information 
you need the correct time of origin, latitude, longitude and depth. You also need the 
correct P and S travel-time model. If any of these parameters are not correct 
WinQuake can't place the markers at the right spot on the seismogram.

If you think you are having a timing problem do the following. Using another source 
for accurate time, I use the USA radio stations WWV/WWVH, jump near the sensor at the 
top of the minute. While your jump may be off by a second you should be able to see 
if the event file timing is off by 10 seconds.

Larry Cochrane

Jón Frímann wrote:
> Hi all
> I think my system did suffer from a GPS connection loss for some unkown
> reasons. This appears to have resaulted in a rater annoying clockdrift.
> Or at least I think so. Clear examples are in my latest traces. I didn't
> notice this, because WinSDR did show (L) as normal. But normally, when
> the GPS clock drops out, it shows (N). The computer clock is in check
> with NTP program that I am running, so drift in the computer clock is
> minimal.
> A earthquake that is 82 km away from me.
> A earthquake that is 182 km away from me.
> Is this a resault of a clock drift or a wrong p and s model. I've would
> like to know. I did reboot the PSN hardware and I think everything is
> back to normal for now, it appears. At least the p and s wave are in
> correct places now.
> Regards.


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