Thread: Fwd: Phase picking

Started: 2011-09-24 02:00:11
Last activity: 2011-09-24 18:19:31
Topics: SAC Help
Abhash Kumar
2011-09-24 02:00:11


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Begin forwarded message:

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

  • Januka Attanayake
    2011-09-24 13:29:51
    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




    Sent from my iPhone

    Begin forwarded message:


    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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  • Arthur Snoke
    2011-09-24 18:19:31
    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
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