Thread: Wiechert seismometer instrumental response

Started: 2015-06-01 15:51:48
Last activity: 2015-06-01 23:43:26
Topics: SAC Help
Carmen Pro
2015-06-01 15:51:48

Hi,

I'd like to know the instrument type for the Wiechert seismometer in SAC when yo use "trans to WIECH", I mean, if it is a velocity or displacement instrumental response and poles and zeros values.

Best,

Carmen Pro

--
_________________________________________
Carmen Pro Muñoz
Dpto. Física- Universidad de Extremadura
Centro Universitario de Mérida
c/ Sta. Teresa de Jornet, nº 38
06800 Mérida (Badajoz)
Tfo. 924 289300- ext:82544
_________________________________________

--
_________________________________________
Carmen Pro Muñoz
Dpto. Física- Universidad de Extremadura
Centro Universitario de Mérida
c/ Sta. Teresa de Jornet, nº 38
06800 Mérida (Badajoz)
Tfo. 924 289300- ext:82544
_________________________________________


  • George Helffrich
    2015-06-01 23:43:26
    Dear Maria Carmen Pro -

    Wiechert instruments had very large masses, giving them effectively a displacement response: i.e. instrument output is proportional to ground displacement. The response built into SAC has:

    Zeros: 2 at (0.,0.)
    Poles: 2 at (-omega0*h, omega0*omega), (-omega0*h, -omega0*omega)

    where omega0 = 2*pi/9.65, h = 0.403712752, and omega = sqrt(1-h**2).

    Response source: AMPLITUDE AND PHASE RESPONSES ARE COMPUTED FROM EQNS. (82), (98), AND (13) OF SOHON (1932), SEISMOMETRY, IN PART II OF INTRODUCTION TO THEORETICAL SEISMOLOGY, J. B. MACELWANE AND F. W. SOHON, JOHN WILEY AND SONS, NEW YORK.

    For a displacement response, the two zeros are puzzling. However, that is what SAC has and I cannot offer any enlightenment as to why or whether it is truly correct. An historical seismologist might be better equipped to explain.

    On 1 Jun 2015, at 15:51, Maria Carmen Pro Munoz <cpro<at>unex.es> wrote:


    Hi,

    I'd like to know the instrument type for the Wiechert seismometer in SAC when yo use "trans to WIECH", I mean, if it is a velocity or displacement instrumental response and poles and zeros values.

    Best,

    Carmen Pro

    --
    _________________________________________
    Carmen Pro Muñoz
    Dpto. Física- Universidad de Extremadura
    Centro Universitario de Mérida
    c/ Sta. Teresa de Jornet, nº 38
    06800 Mérida (Badajoz)
    Tfo. 924 289300- ext:82544
    _________________________________________

    --
    _________________________________________
    Carmen Pro Muñoz
    Dpto. Física- Universidad de Extremadura
    Centro Universitario de Mérida
    c/ Sta. Teresa de Jornet, nº 38
    06800 Mérida (Badajoz)
    Tfo. 924 289300- ext:82544
    _________________________________________

    _______________________________________________
    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



    • Carmen Pro
      2015-06-01 19:05:58
      Thank you very much

      Best regards
      Carmen Pro
      ----- Mensaje original -----
      De: George Helffrich <George.Helffrich<at>bristol.ac.uk>
      Para: Maria Carmen Pro Munoz <cpro<at>unex.es>
      CC: sac-help<at>iris.washington.edu
      Enviado: Mon, 01 Jun 2015 09:43:26 +0200 (CEST)
      Asunto: Re: [SAC-HELP] Wiechert seismometer instrumental response

      Dear Maria Carmen Pro -

      Wiechert instruments had very large masses, giving them effectively a displacement response: i.e. instrument output is proportional to ground displacement. The response built into SAC has:

      Zeros: 2 at (0.,0.)
      Poles: 2 at (-omega0*h, omega0*omega), (-omega0*h, -omega0*omega)

      where omega0 = 2*pi/9.65, h = 0.403712752, and omega = sqrt(1-h**2).

      Response source: AMPLITUDE AND PHASE RESPONSES ARE COMPUTED FROM EQNS. (82), (98), AND (13) OF SOHON (1932), SEISMOMETRY, IN PART II OF INTRODUCTION TO THEORETICAL SEISMOLOGY, J. B. MACELWANE AND F. W. SOHON, JOHN WILEY AND SONS, NEW YORK.

      For a displacement response, the two zeros are puzzling. However, that is what SAC has and I cannot offer any enlightenment as to why or whether it is truly correct. An historical seismologist might be better equipped to explain.

      On 1 Jun 2015, at 15:51, Maria Carmen Pro Munoz <cpro<at>unex.es> wrote:


      Hi,

      I'd like to know the instrument type for the Wiechert seismometer in SAC when yo use "trans to WIECH", I mean, if it is a velocity or displacement instrumental response and poles and zeros values.

      Best,

      Carmen Pro

      --
      _________________________________________
      Carmen Pro Muñoz
      Dpto. Física- Universidad de Extremadura
      Centro Universitario de Mérida
      c/ Sta. Teresa de Jornet, nº 38
      06800 Mérida (Badajoz)
      Tfo. 924 289300- ext:82544
      _________________________________________

      --
      _________________________________________
      Carmen Pro Muñoz
      Dpto. Física- Universidad de Extremadura
      Centro Universitario de Mérida
      c/ Sta. Teresa de Jornet, nº 38
      06800 Mérida (Badajoz)
      Tfo. 924 289300- ext:82544
      _________________________________________

      _______________________________________________
      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


      --
      _________________________________________
      Carmen Pro Muñoz
      Dpto. Física- Universidad de Extremadura
      Centro Universitario de Mérida
      c/ Sta. Teresa de Jornet, nº 38
      06800 Mérida (Badajoz)
      Tfo. 924 289300- ext:82544
      _________________________________________


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