Thread: a question about transfer command in Sac

Started: 2009-07-12 23:06:41
Last activity: 2009-07-14 00:56:28
Topics: SAC Help
reza
2009-07-12 23:06:41
Hi
I have a problem with transfer command in Sac.
I have removed an instrument response and applied Wood Anderson to a
wave in two different ways but I saw some problems.

First, I removed SS1 response with: transfer from polezero subtype
$resp freq 1 10, then I applied WA response with this command:
transfer to WA
Furthermore, I did both with this command: transfer from polezero
subtype $resp to WA freq 1 10

From the above you might got idea that the result should be similar,
but the results from the first and the second method are not similar.

I have attached a file. Please run and look at the script in it. You
can change parameters and test it. I am very grateful if you help me.

Thanks,
Reza

Attachments
  • Arthur Snoke
    2009-07-12 23:15:32
    I have been working on the transfer function, so I looked at your example.

    A few comments:

    It is not clear which version of sac you are using, as your command is
    sac2000. It probably does not matter.

    The command sequence

    rmean
    rtr

    could be replaced by

    rtr

    only. Try both ways and compare the lh output.

    The command FREQ (short for FREQLIMITS) should have 4 arguments. I am not
    sure what it means if you put in only two. I am guessing that you want
    the filter response flat between 1 and 10 Hz.

    Here is a run with settings I think do what you want. I did not do all
    the tests. Recall that a second call to transfer with no FREQ will
    probably use the values from the first time. Not sure that is what you
    want.

    SAC> r 2000-08-03-0620-19S.TBZ___001_SP_E_TBZ___SP_E_SAC
    SAC> rtr
    Slope and standard deviation are: -0.00089445 0.14512
    Intercept and standard deviation are: 0.13525 22.458
    Data standard deviation is: 1300.1
    Data correlation coefficient is: 5.3244e-05
    SAC> transfer from polezero subtype ss1rd3_2.pz to WA FREQ 0.1 1.0 10.0
    20.0
    Extracting polezero response for TBZ SP , SP E ...

    Station (TBZ SP ), Channel (SP E )
    Waveform multiplied by 1.000000 after deconvolution.
    SAC> p1
    SAC> ppk
    SAC> write wa.sac
    SAC> quit

    Let me know if you (aor anyone else) have questions about what I am doing
    or claiming, as I want the next writeup on transfer to be both complete
    and accurate.

    Arthur Snoke

    On Sun, 12 Jul 2009, reza rezaei wrote:

    Hi
    I have a problem with transfer command in Sac.
    I have removed an instrument response and applied Wood Anderson to a
    wave in two different ways but I saw some problems.

    First, I removed SS1 response with: transfer from polezero subtype
    $resp freq 1 10, then I applied WA response with this command:
    transfer to WA
    Furthermore, I did both with this command: transfer from polezero
    subtype $resp to WA freq 1 10

    From the above you might got idea that the result should be similar,
    but the results from the first and the second method are not similar.

    I have attached a file. Please run and look at the script in it. You
    can change parameters and test it. I am very grateful if you help me.

    Thanks,
    Reza


  • Arthur Snoke
    2009-07-14 00:56:28
    When running the SAC TRANSFER a second time within a SAC session, it
    remembers the settings for things like FROM and TO and FREQ from the first
    run. Hence in Reza's example,

    SAC> r 2000-08-03-0620-19S.TBZ___001_SP_E_TBZ___SP_E_SAC
    SAC> rtr
    SAC> transfer from polezero subtype ss1rd3_2.pz freq 0.1 1 10 12

    followed by

    SAC> transfer to WA

    actually was translated by SAC as the complete command

    transfer from polezero subtype ss1rd3_2.pz to WA freq 0.1 1 10 12

    which is what he did in his second run, but the waveform has been
    transformed by the first transform.

    One could either follow the first transfer with a

    SAC r
    SAC> transfer to WA

    or one could write out the waveform after the first transfer

    SAC> write try0.sac
    SAC> quit

    Restart SAC

    SAC> r try0.sac
    SAC> transfer to WA
    SAC> write try4.sac

    Shown in the attached plot is a plot of this try4 and try2, which was
    written applying the two-stage transfer to the original waveform.

    Arthur
    Attachments
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