Separation of intrinsic and scattering Q by envelope inversion

Qopen is a script in seismology that estimates shear wave scattering and intrinsic attenuation parameters by inversion of seismogram envelopes.

The method is described in the following publication:

Tom Eulenfeld and Ulrich Wegler (2016), Measurement of intrinsic and scattering attenuation of shear waves in two sedimentary basins and comparison to crystalline sites in Germany, Geophysical Journal International, 205(2), 744-757, doi:`10.1093/gji/ggw035`__. [pdf]

Alternatively, have a look at our poster presented at the 2015 Annual Meeting of the DGG.

Since version 2, Qopen runs on Python3 only. If you want to use Qopen with Python2 use version 1.x.

Dependencies of Qopen are:

• ObsPy>=1.0
• NumPy, SciPy and matplotlib (itself dependencies of ObsPy)
• statsmodels

Installation with conda -it's probably best to install ObsPy and other dependencies first and then let pip take care of the rest:

conda --add channels conda-forge
conda create -n qenv matplotlib numpy scipy obspy statsmodels
conda activate qenv
pip install qopen

Qopen provides the scripts qopen, qopen-rt and qopen-runtests. The installation can be tested with:

qopen-runtests

The code is run by the installed command line script qopen. A tutorial can be created with the appropriate flag:

qopen --tutorial

This command copies an example configuration file in JSON format and the corresponding data files into the current directory. The configuration file is heavily commented and should be rather self-explanatory. Now you can perform the inversion by simply running :

qopen

which will calculate the results and create different plots.

To use the script with your own data you need 1. an inventory (StationXML or other ObsPy readable format) of your stations, 2. the earthquake catalog (QuakeML or other ObsPy readable format) preferable with P and S picks and 3. the waveforms. Waveforms may exist in data files of various formats or can be fetched from a webservice. A custom solution for waveform retrieval is also possible (e.g. mixing of data files and web requests). An example configuration file can be created with :

qopen --create-config

This file has to be adapted to your needs (time window selection, etc.). The inversion is started by simply running qopen again.

To call Qopen from Python do e.g. :

from qopen import run
run(conf='conf.json')

All configuration options in conf.json can be overwritten by keyword arguments passed to run().

Qopen can be "abused" to determine a mean coda Q with the diffusion approximation with the following settings in conf.json:

"optimize": null,
"bulk_window": null,
"G_plugin": "qopen.rt : G_diffapprox3d",
"seismic_moment_method": null,

The scattering coefficient and event spectra are meaningless with these settings. Qi corresponds to Qc in this case. For the single scattering approximation use a user-defined Green's function.

For comparison, Qopen can be used with coda normalization with the following settings in conf.json:

"coda_normalization": [180, 200],
"seismic_moment_method": null,

Of course, site amplifications and event spectra are useless in this case.

Please consult the API documentation.

The seistools mailing list can be used to contact other users and developers.

A somewhat advanced example using the Qopen package: USAttenuation.

These studies make use of Qopen: Google Scholar Link.