PSN-L Email List Message

Subject: On timing
From: Kevin McCue asc@...............
Date: Mon, 11 Apr 2005 14:17:51 +1000

Reluctant as I was to get involved in a good story,=A0=A0Chris=20
Chapman=A0=A0finally got me in with:

'=A0I agree that you can't use the sub microsecond accuracy of a good =
clock. However, if your clock only had an accuracy of 1 sec, you would=20=

have a possible error of ~10 km. If it had an error of 10 sec, the=20
possible error is ~100 km. Neither would be particularly helpful when=20
estimating the depth of a quake at, say 40 km, or of it's position. I'm=20=

sorry to put it so bluntly, but if you CAN'T give error limits to your=20=

measurements, you are JUST COLLECTING GARBAGE !'

You can use S-P intervals to locate the epicentre, travel time curves=20
to compute an origin time and depth-phase identification to sort out=20
focal depth - one could get away without accurate time at all, but it=20
makes life easier.

Kevin McCue
Australian Seismological Centre
PO Box 324 Jamison Centre
ACT 2614
ph: 61 (0)2 6251 1291=


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