Thread: CORRELATION

Started: 2021-10-23 03:10:38
Last activity: 2021-10-25 16:05:30
Topics: SAC Help
M. Zafar Iqbal Seismologist
2021-10-23 03:10:38
Hi. I want to cross-correlate two stations. I have waveforms in sac format. When I use “correlate” , its done but in writing the correlated waveform, I have to provide two names. I checked the header, there is no change in header which I think there should be information of two stations. What to do?

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  • George Helffrich
    2021-10-25 16:05:30
    Dear M. Zafar Iqbal -

    SAC’s CORRELATE command works on two or more traces. The master seismogram (by default the first) is turned into its autocorrelation and the second (and further) trace(s) are cross-correlated with the master.

    If you have two seismograms in memory to start with, you will have two correlations in memory after CORRELATE. If you don’t want the autocorrelation, delete it with the DELETECHANNEL command (for example, DC 1). Then you can write out only the cross-correlation as a single SAC file.

    SAC should preserve the station information in the header, but the begin and end times will change to lags relative to the file zero time.

    On 25 Oct 2021, at 09:49, M. Zafar Iqbal Seismologist (via IRIS) <sac-help-bounce<at>lists.ds.iris.edu> wrote:

    Hi. I want to cross-correlate two stations. I have waveforms in sac format. When I use “correlate” , its done but in writing the correlated waveform, I have to provide two names. I checked the header, there is no change in header which I think there should be information of two stations. What to do?

    Sent from Mail https://go.microsoft.com/fwlink/?LinkId=550986 for Windows 10


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    George Helffrich
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