Characteristics on Bode plot using Inventory.plot_response

Users Mailing List Archive
1

Dear people of ObsPy,

where can I find some details (documentation) about 2 highlighted numbers on
Bode plot using Inventory.plot_response (see [1])?

* Right value shows plateau of amplitudes -- it's clear for me;
in [1]: 9.4e+08.
* But top value (in [1]: 0.02Hz = 50s) often don't show expected flat regions
lower corner frequency. Without knowledge of example's details I would expect
in case [1] something around 0.01Hz = 100s (probably 120s = STS2?). At least
one of my STS2-plots shows exactly the same unexpected value.

In my examples in 6 of 7 cases highlighted frequency don't match lower corner,
but in one case it fits well. So it could be possible that I'm wrong to expect
lower corner frequency for highlighting - but what else frequency could be
highlighted otherwise?

Best Regards
Sigward

[1] https://docs.obspy.org/packages/autogen/
obspy.core.inventory.response.Response.plot.html

Sfunke.vcf (168 Bytes)

2

Hi Sigward,

the values you see as annotations to the amplitude spectrum in the Bode
plot are simply what is specified for the overall sensitivity in the
given station metadata:

from obspy import read_inventory
response = read_inventory()[0][0][0].response
print(response)
print(response.instrument_sensitivity)

Instrument Sensitivity:
  Value: 943680000.0
  Frequency: 0.02
  Input units: M/S
  Input units description: Velocity in Meters per Second
  Output units: COUNTS
  Output units description: Digital Counts

Usually this should be within the flat part of the response.

best,
Tobias

3

Hi Tobias,

thanks for fast and clear explanation. So not corner frequency is annotated
but frequency of overall sensitivity - makes sense.

Best Regards
Sigward