[obspy-users] Question regarding removing instrument response with a PAZ dictionary

Claire Masteller mastell at gfz-potsdam.de
Wed Mar 6 15:31:10 CET 2019


Hi all,



Apologies in advance for the basic question, but I am a new Obspy user. I’m
attempting to remove instrument response using a PAZ dictionary.  The
set-up I am using is a Trilium Compact 120s with an Omnirecs DataCube3
datalogger and I’m sampling at 200 Hz.



I have the following values for the instrument and datalogger combination
and am not quite sure how to incorporate all of them into the dictionary
and instrument response removal process correctly. Specifically, I am not
quite sure where to incorporate the logger AD factor relative to the ground
motion sensitivity.



Relevant values:

*Signal gain:* 4.0

*Ground motion sensitivity F0 *= 75.43 V/(m/s)

*6 Zeros (rad/s)*
z1 = 0
z2 = 0
z3 = -392
z4 = -1960
z5/6 = -1490 ±1740i

*11 Poles (rad/s)*
p1/2 = -0.03691 ±0.03702i
p3 = -343
p4/5 = -370  ±467i
p6/7 = -836  ±1522i
p8/9 = -4900  ±4700i
p10 = -6900
p11 = -15000

*Normalization factor*
a = 4.34493 x 1017

*Normalization frequency (Hz)*
f0 = 1

*Logger AD factor:* 2.4414e-07



So far, playing around with the code, my best guess has been to divide F0
by AD, but I am only guessing here. However, when I compare the output to
code written to remove instrument response by a colleague in R, there are
significant differences in the output (see below), so I’m clearly doing
something wrong.



Anyway, any feedback/help on this would be much appreciated.



Code and sample output attached below.



Thank you,

Claire



>From tutorials on the Obspy website I’ve generated the following code:

* To build the dictionary:*
[image: image.png]
*To remove instrument response:*
[image: image.png]



*Output with my code:*


[image: image.png]

*Output with my colleague’s R code of same data:*
[image: image.png]
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