PSN-L Email List Message

Subject: Re: Honduras quake 5/28
From: Bob Hancock icarus@.........
Date: Thu, 28 May 2009 06:52:09 -0700


I checked the P arrival time time at my station TPA  (32.100883   
-111.334383) using the USGS Phase arrival time program, and the  
variance was + 0.7 seconds.  The computed travel time was 345.93  
seconds.  See link for program.

http://neic.usgs.gov/neis/travel_times/compute_tt.html

I then checked the arrival time using the TauP Toolkit program  
available through either iIRIS, or the University of South Carolina.   
The travel time was listed as 344.93 seconds, and the variance was  
-0.3 sec.  NOTE - This is a Java based program.

These timing differences are normal and the result of different  
material that the waves pass through.

A 30 second variance suggests that the timing used at your station was  
off.

Bob Hancock

On May 28, 2009, at 4:37 AM, Thomas Dick wrote:

> Anybody else having trouble using USGS data and finding P off by as  
> much as 30 seconds?
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