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

Ringler, Adam aringler at usgs.gov
Wed Mar 6 18:15:36 CET 2019


Hello Claire,

In the python code you attached it looks like you are removing the response
sts2 and then convolving with the inst2hz.  You have inst2hz set to be an
instrument with a 100 Hz corner.  If you are trying to go to units of
velocity, then you don't want to simulate a new response.

E.g. for a 120 s compact on a Q330HR you might do something like:

pazvel = {'zeros': [0., 0., -392.0, -1960.0, -1490.0 + 1740.0j, -1490.0 -
1740.0j],
            'poles': [-0.03691 + 0.03702j, -0.03691 - 0.03702j, -343.0,
-370.0 + 467.0j, -370.0 - 467.0j, -836.0 + 1522.0j,
                    -836.0 - 1522.0j, -4900.0 + 4700.0j, -4900.0 - 4700.0j,
-6900.0, -15000.0], 'gain': 4.344928*(10**17),
                    'sensitivity': 754.3*(2**26/40.)}

stvel.simulate(paz_remove = pazvel)

Hopefully this helps a bit.  I apologize if this isn't helpful for what you
are trying to do.

Best,
Adam

On Wed, Mar 6, 2019 at 9:56 AM Claire Masteller <mastell at gfz-potsdam.de>
wrote:

> 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]
>
>
> _______________________________________________
> obspy-users mailing list
> obspy-users at lists.swapbytes.de
> https://lists.swapbytes.de/mailman/listinfo/obspy-users
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