Thread: RMS of spectral Amplitude

Started: 2014-01-19 03:38:11
Last activity: 2014-01-19 09:27:05
Topics: SAC Help
mostafa
2014-01-19 03:38:11
Hi
I want to ask if there is any way to get the RMS of Spectral Amplitude in sac ? RMS command in SAC is design for time domain, although it works in frequency domain also but I am not sure about the results. I need to measure the spectral amplitude and I am seeking a way more dependable than taking a maximum amplitude. Is the Hilbert transforming and taking maximum amplitude afterward a good alternative for taking RMS?
Sincerely



S. Mostafa Mousavi
Ph.D. candidate, Geophysics
Center for Earthquake Research and Information
University of Memphis
3876 Central Ave, Suite 3
Memphis, TN 38152
Phone: +1 (202) 304-0084
Email: smousavi<at>memphis.eduhttps://sn2prd0410.outlook.com/owa/redir.aspx?C=aWxCKi-ybkuNzkngCW4UFod6DJLVic8IR52CYvkFuQVTN3CKpjpRKsER7oScRDeVStU6bxWnbGw.&URL=mailto%3abayoung6%40memphis.edu

  • George Helffrich
    2014-01-19 07:19:05
    Dear Mostafa Mousavi -

    You want to use the WRITESP command to write out your spectrum after FFT, then read back in the file as a time series, e.g.

    fg seismogram; fft; writesp am /tmp/fft; read /tmp/fft.am; rms

    On 18 Jan 2014, at 19:38, S Mousavi (smousavi) wrote:

    Hi
    I want to ask if there is any way to get the RMS of Spectral Amplitude in sac ? RMS command in SAC is design for time domain, although it works in frequency domain also but I am not sure about the results. I need to measure the spectral amplitude and I am seeking a way more dependable than taking a maximum amplitude. Is the Hilbert transforming and taking maximum amplitude afterward a good alternative for taking RMS?
    Sincerely


    S. Mostafa Mousavi
    Ph.D. candidate, Geophysics
    Center for Earthquake Research and Information
    University of Memphis
    3876 Central Ave, Suite 3
    Memphis, TN 38152
    Phone: +1 (202) 304-0084
    Email: smousavi<at>memphis.edu
    _______________________________________________
    sac-help mailing list
    sac-help<at>iris.washington.edu
    http://www.iris.washington.edu/mailman/listinfo/sac-help



    George Helffrich
    george.helffrich<at>bris.ac.uk


    • mostafa
      2014-01-19 09:27:05
      Thanks for reply, but can we trust the value we get in this way? mathematically RMS calculated in time domain should be the same as frequency domain. But using this way I am getting different values.

      Best Regards

      Mostafa



      ________________________________
      From: George Helffrich <glgrh<at>bristol.ac.uk> on behalf of George Helffrich <George.Helffrich<at>bristol.ac.uk>
      Sent: Saturday, January 18, 2014 11:19 PM
      To: S Mousavi (smousavi)
      Cc: sac-help<at>iris.washington.edu
      Subject: Re: [SAC-HELP] RMS of spectral Amplitude

      Dear Mostafa Mousavi -

      You want to use the WRITESP command to write out your spectrum after FFT, then read back in the file as a time series, e.g.

      fg seismogram; fft; writesp am /tmp/fft; read /tmp/fft.am; rms

      On 18 Jan 2014, at 19:38, S Mousavi (smousavi) wrote:


      Hi
      I want to ask if there is any way to get the RMS of Spectral Amplitude in sac ? RMS command in SAC is design for time domain, although it works in frequency domain also but I am not sure about the results. I need to measure the spectral amplitude and I am seeking a way more dependable than taking a maximum amplitude. Is the Hilbert transforming and taking maximum amplitude afterward a good alternative for taking RMS?
      Sincerely


      S. Mostafa Mousavi
      Ph.D. candidate, Geophysics
      Center for Earthquake Research and Information
      University of Memphis
      3876 Central Ave, Suite 3
      Memphis, TN 38152
      Phone: +1 (202) 304-0084
      Email: smousavi<at>memphis.eduhttps://sn2prd0410.outlook.com/owa/redir.aspx?C=aWxCKi-ybkuNzkngCW4UFod6DJLVic8IR52CYvkFuQVTN3CKpjpRKsER7oScRDeVStU6bxWnbGw.&URL=mailto%3abayoung6%40memphis.edu
      _______________________________________________
      sac-help mailing list
      sac-help<at>iris.washington.edu<sac-help<at>iris.washington.edu>
      http://www.iris.washington.edu/mailman/listinfo/sac-help



      George Helffrich
      george.helffrich<at>bris.ac.uk<george.helffrich<at>bris.ac.uk>


18:16:34 v.22510d55