Thread: Normalization in -1 1 range

Started: 2022-10-19 16:11:46
Last activity: 2022-10-20 10:53:02
Topics: SAC Help
Joana Carvalho
2022-10-19 16:11:46
Hello SAC users

I am trying to normalize some sac files. I know how to normalize to 1 using the max amplitude but I want to both max and min amplitude and thus normalize my negative amplitude to -1 and the positive to 1.

Is it possible to do it in SAC?

I let you a file to use as example.

Thanks in advance, and I am sorry if this is not the proper way to ask for help.

Joana Carvalho
Attachments
  • Geo .
    2022-10-20 10:53:02
    Hi Joana,
    Not sure if I understand your question correctly. If you want to normalise
    both positive and negative peak amplitudes to 1 and -1 respectively, you
    can't do it without distorting the original waveform. I don't know if this
    can be done in SAC as you'd scale your positive amplitudes differently than
    negative amplitudes.

    However, if you meant that you want to normalise your trace by absolute
    peak amplitude (regardless of it being positive or negative), you can use
    the following macro.

    READ My.SAC
    SETBB normax &1,DEPMAX
    SETBB normin &1,DEPMIN
    SETBB normamp (MAX (ABSOLUTE %normax) (ABSOLUTE %normin))
    GETBB normamp
    DIV %normamp
    WRITE PREPEND NORM_PEAK_
    MESSAGE '------------------------'
    QUIT
    END

    Januka

    Januka Attanayake
    Research Fellow/Lecturer | Earthquake Seismology Lead
    Homepage: *https://sites.google.com/site/janukaattanayake
    https://sites.google.com/site/janukaattanayake*

    School of Geography, Earth & Atmospheric Sciences
    University of Melbourne | Parkville 3010 VIC
    Australia




    On Thu, 20 Oct 2022 at 05:02, Joana Carvalho (via IRIS) <
    sac-help-bounce<at>lists.ds.iris.edu> wrote:

    Hello SAC users

    I am trying to normalize some sac files. I know how to normalize to 1
    using the max amplitude but I want to both max and min amplitude and thus
    normalize my negative amplitude to -1 and the positive to 1.

    Is it possible to do it in SAC?

    I let you a file to use as example.

    Thanks in advance, and I am sorry if this is not the proper way to ask for
    help.

    Joana Carvalho
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