Thread: Fwd: Phase picking

You can cross check if your timing is correct independently with something like Taup tool kit. Also, you might be able to use the header OMARKER to double check.
 
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________________________________
From: Abhash Kumar <abhash.kumar84<at>gmail.com>
To: "sac-help<at>iris.washington.edu" <sac-help<at>iris.washington.edu>
Sent: Friday, September 23, 2011 7:00 PM
Subject: [SAC-HELP] Fwd: Phase picking




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From: akumar <abhash.kumar84<at>gmail.com>

Date: September 23, 2011 4:27:08 PM EDT
To: sac-help<at>iris.washington.edu
Subject: Phase picking

Hi,

I am using SAC to pick events on vertical component and then using rot command to rotate east and north to radial and transverse. I have picked P-wave arrival on vertical component and it has generated a time marker at 305.45 seconds from the reference time. For S-wave, I have used transverse component and the time marker is at 269.67 seconds, which is less than P-wave arrival time. I looked into header file and it says that B value for vertical component is 0.00second but for transverse it is -67.00 seconds and adding this time to S-wave time marker gives time of 336.67 seconds, which is more than P-wave arrival time. I was wondering, do I need to add this B value to the S-wave time marker in the header file, otherwise when I will be extracting the data at later stage then it will show the discrepancy of S-wave travel time less than P-wave travel time. I would really appreciate any kind of suggestion.

Thanks
Abhash Kumar
University of North Carolina at chapel hill
NC

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For the rotate command to work, your two horizontal components have to be
matched in terms of B and npts. To interpret the results, it is best if
they have the same B as the vertical component. Also, to interpret the P
and S arrival times, it is probably a good idea to change iztype to origin
time (if you know it) for all three components. It sounds like you have
iztype set to begin time for the vertical and something else for the
horizontals.

From: akumar <abhash.kumar84<at>gmail.com>
Date: September 23, 2011 4:27:08 PM EDT
To: sac-help<at>iris.washington.edu
Subject: Phase picking

Hi,
I am using SAC to pick events on vertical component and then
using rot command to rotate east and north to radial and
transverse. I have picked P-wave arrival on vertical component
and it has generated a time marker at 305.45 seconds from the
reference time. For S-wave, I have used transverse component and
the time marker is at 269.67 seconds, which is less than P-wave
arrival time. I looked into header file and it says that B value
for vertical component is 0.00second but for transverse it is
-67.00 seconds and adding this time to S-wave time marker gives
time of 336.67 seconds, which is more than P-wave arrival time.
I was wondering, do I need to add this B value to the S-wave
time marker in the header file, otherwise when I will be
extracting the data at later stage then it will show the
discrepancy of S-wave travel time less than P-wave travel time.
I would really appreciate any kind of suggestion.

Thanks
Abhash Kumar
University of North Carolina at chapel hill