[SAC-HELP] Removing Instrument Response

Arthur Snoke snoke at vt.edu
Sun Aug 28 14:55:38 PDT 2011


Some of the messages may be caused by the fact that the header variable 
SCALE is defined.  After reading in file.sac, try

SAC> scale unset

and then do the transfer.

Depending on the kind of seismometer you have and the insrument bandpass, 
the output may not look the same as the input.

SAC version 101.5 (coming soon) does not use scale, and RDSEED 5.1 does 
not put anything in the SCALE sac header.

On Sun, 28 Aug 2011, James Smith wrote:

> Hello:
>
> I have a set of Canadian seismograms that I need to remove the
> instrument response from. I have converted the seed files to sac files
> and extracted the RESP files.  I am using the following commands in
> SAC:
>
> sac> file.sac
> sac> rmean
> sac> rtrend
> sac> taper
> sac> trans from evalresp to none freq .01 .015 2 5
>
> When I use the evalresp file I get the following output:
>
> Nominal Calper not set. Setting Nominal Calper to -999.000000 to
> match Wfdisc Calper
> Sensor Calper not set. Setting Sensor Calper to 1.000000 to match Wfdisc Calper
> Response appears to be Un-Normalized.
> Waveform appears to be unscaled.
> Wfdisc calib value is (769600000.000000).
> Waveform multiplied by 1.000000 after deconvolution.
>
> The deconvolved seismogram usually doesn't resemble the original. My
> understanding is that removing the instrument response should not in
> general change the shape of the seismogram. I've tried applying
> various bandpass filters without much luck.
>
> Can anyone tell me if I am missing a step or what could be responsible
> for my problem?
>
> Thanks,
>
> James Smith
> Colorado State University



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