Thread: Help with polezero, transfer to vel and acc

Started: 2010-05-29 05:13:37
Last activity: 2010-05-29 05:13:37
Topics: SAC Help
Danilo Domingos
2010-05-29 05:13:37
Hello everyone!
Ok, where to begin?
I have to calculate the PGA (peak ground acceleration) of some
events, and to do that I have 2 options:
1) Use the SAC function TRANSFER to convert the original
displacement data to acceleration.
2) Manually convert the data to velocity (using seismometer and
digitizer parameters), and then differenciate to acc.
Why is this 2nd option there?
Because I've tried to understant how to build the POLEZERO file too
many times. The poles and zeros aren't a problem (I've found them in
the seismometer manual), but to find the constant value, I've seen a
lot of formulas. One of them is:
CONSTANT = A0 * SensorGain * DigitizerGain
where A0 is the "normalization factor". I can't find it in the
seismometer manual. Theese are the informations I have about
seismometer and digitizer:
- Seismometer: KS2000 Geotech Instruments
- Seismometer seismic output: 40V pp
- Seismometer sensibility: 2000 v/m/s
- Digitizer: SMART24 Geotech Instruments
- Digitizer LSB value for 40V pp: 3.271096e-6 V/count
- Digitizer Gain: x 64 (multiplication)
As far as I know, displacement data is given in counts
Any ideas with the constant calculation? or should I try to
calculate acc manually with the conversion to velocity (using
parameters) and the differentiating?
Thank you very much.
----------------------------------------------------------
Danilo de Oliveira Domingos
University of São Paulo
Brazil

  • Arthur Snoke
    2010-05-29 01:40:53
    The relation you cite is based on a polexzero file that has been obtained
    by using RDSEED on a SEED volume for an event using that station.

    If you have a polezero file, the documentation for that file will
    hopefully tell you how to interpret CONSTANT. Others on the list may know
    the characteristics for your system and provide your answer.

    On Fri, 28 May 2010, Danilo Domingos wrote:

    Hello everyone!
    Ok, where to begin?

    I have to calculate the PGA (peak ground acceleration) of some events, and
    to do that I have 2 options:

    1) Use the SAC function TRANSFER to convert the original displacement data
    to acceleration.
    2) Manually convert the data to velocity (using seismometer and digitizer
    parameters), and then differenciate to acc.

    Why is this 2nd option there?
    Because I've tried to understant how to build the POLEZERO file too many
    times. The poles and zeros aren't a problem (I've found them in the
    seismometer manual), but to find the constant value, I've seen a lot of
    formulas. One of them is:
    CONSTANT = A0 * SensorGain * DigitizerGain

    where A0 is the "normalization factor". I can't find it in the seismometer
    manual. Theese are the informations I have about seismometer and digitizer:

    - Seismometer: KS2000 Geotech Instruments
    - Seismometer seismic output: 40V pp
    - Seismometer sensibility: 2000 v/m/s

    - Digitizer: SMART24 Geotech Instruments
    - Digitizer  LSB value for 40V pp: 3.271096e-6 V/count
    - Digitizer Gain: x 64 (multiplication)

    As far as I know, displacement data is given in counts

    Any ideas with the constant calculation? or should I try to calculate acc
    manually with the conversion to velocity (using parameters) and the
    differentiating?

    Thank you very much.

    ----------------------------------------------------------
    Danilo de Oliveira Domingos
    University of São Paulo
    Brazil



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