This is the correct address. However, I cannot follow the logic in your
message so (for me at least) you need to provide more information.
By construction, a pole-zero file is causal. However, if you include with
that step a "freqlimits" call, that call is not causal. The number of
poles for a p-z file depends on whether you are correcting to
displacement, velocity, etc. If your data came from a SEED volume, the
RESP file makes clear what the correction is for.
For use to help, you need to provide more information. If you have not
already, I suggest you look at the transfer help file:
http://www.iris.edu/software/sac/commands/transfer.html.
On Fri, 6 May 2011, Ivan Lokmer wrote:
Dear Colleague,
I hope that I am at the right address to launch my question.
I was using SAC polezero option recently to remove the instrument response
from my data and to add it to synthetics.
However, I realized that this option is acting as a 2-pass acausal filter. AS
the actual seismometer filters the ground motion as 1-pass causal filter, it
seems to me that it is impossible to recover actual ground motion by using
this option.
It is not very obvious with very band limited data, but it is more than
obvious for the data with static shift, where the waveform is changed before
time 0 (which is impossible for any physical device including seismometer).
Do you maybe know if there's any option in SAC that will add/remove
instrument's response as of the actual physical device (causally)?
Thank you in advance for your answer
A great job is done with all the manuals and software. Thanks for that
Kind regards,
Ivan
--
______________________________________________
Ivan Lokmer
Seismology and Computational Rock Physics Lab.
Geophysics Group School of Geological Sciences
University College Dublin
Belfield
Dublin 4
Ireland
Phone: +353 1 7162079
Fax: +353 1 2837733
Mobile:+353 87 2553638
Ivan
Arthur Snoke
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