[SAC-HELP] Fwd: Phase picking

[Arthur Snoke]

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