how to get PZ from stationXML inventory

Users Mailing List Archive
1

Dear All,

I am trying to get PZ information from stationXML.
It is quite easy to read the station XML files with read_inventory, and to remove the response using the remove_response, but I would like to get the PZ coeffecient from the stationXML because I want to plot the sensor response.

In fact I would like to do something like getPAZ method in the Parser class in xseed, but fro the stationXML format.

Is there any existing solution ? I try Inventory.Response method, but It does not give me explicitly the PZ values :

Channel Response
    From None (None) to None (None)
    Overall Sensitivity: 1.25435e+11 defined at 1.000 Hz
    5 stages:
        Stage 1: PolesZerosResponseStage from M/S to V, gain: 1168.20
        Stage 2: CoefficientsTypeResponseStage from V to COUNTS, gain: 107374000.00
        Stage 3: FIRResponseStage from COUNTS to COUNTS, gain: 1.00
        Stage 4: FIRResponseStage from COUNTS to COUNTS, gain: 1.00
        Stage 5: FIRResponseStage from COUNTS to COUNTS, gain: 1.00

There is also the method "get_evalresp_response" but does not exactly give me the PZ values...only the frequency simulation of the equivalent filter....

Thanks in advance,

Best regards
Mickael.

2

Hi Mickael,

its fairly easy to assemble the PAZ dictionary from full inventory objects. You just have to extract the information from the correct response stages.

response = inv[0][0][0].response

Overall sensitivity:

response.instrument_sensitivity.value

PAZ are usually the first stage.

poles = response.response_stages[0].poles
zeros = response.response_stages[0].zeros
norm_fact = response.response_stages[0].normalization_factor
stage_gain = response.response_stages[0].stage_gain

I guess this is all that’s needed.

Hope it helps!

Lion

3

Hi Mickael,

both things you mentioned are already implemented in the master branch
of ObsPy (but not in latest stable release 0.9.2).

http://docs.obspy.org/master/packages/autogen/obspy.station.inventory.Inventory.plot_response.html

http://docs.obspy.org/master/packages/autogen/obspy.station.response.Response.get_paz.html

If switching to the developer version of ObsPy is not an option,
extracting the poles and zeros information should be pretty simple to
do, just have a look at this code:

https://github.com/obspy/obspy/blob/3b1e65ef27c4477ce7165e4e18a2a4f99bc3eb3a/obspy/station/response.py#L1280-L1335

best,
Tobias

4

Thanks Lion,

That's gives me good a solution.

Regards.

Mickaël LANGLAIS

5

Hi Tobias,

Thanks for this extra information.

When does the master branch will be released into stable ?

I try to take advantage of the response.py, but my python skills does not give me enough experience to include this file successfully. Any tips ?

Thanks in advance,

Mickaël LANGLAIS

6

Hi Mickael,

When does the master branch will be released into stable ?

no fixed date there, whenever we find time to tie up some loose ends..

I try to take advantage of the response.py, but my python skills does
not give me enough experience to include this file successfully. Any tips ?

I did not want to suggest that you should include that file.. just that
you can take some inspiration from the code pieces I highlighted in that
link..

best,
Tobias