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.
How it works
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.
How to use it
Dependencies of Qopen are:
- NumPy, SciPy and matplotlib (itself dependencies of ObsPy)
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 and qopen-runtests. The installation can be tested with:
The code is run by the installed command line script qopen. A tutorial can be created with:
qopen create --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 :
which will calculate the results and create different plots.
A more extensive tutorial is available here.
Use your own data
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:
This file has to be adapted to your needs (time window selection, etc.). The inversion is started by simply running qopen again.
Available Qopen commands
Available Qopen commands can be displayed with
create Create example configuration in specified file (default: conf.json) go Estimate intrinsic attenuation and scattering strength, site responses, event spectra (including source parameters) by inversion of envelopes fixed Estimate site responses and event spectra (including source parameters) with fixed attenuation parameters (g0, b) by inversion of envelopes source Estimate event spectra and derive source parameters, e.g. moment magnitude, with fixed attenuation parameters (g0, b) and fixed site responses by inversion of envelopes recalc_source Derive source parameters from source spectra without new inversion (possibly changed configuration, e.g. seismic_moment_options) plot Replot results. Can be used together with -e to plot event results rt Calculate or plot spectral energy densitiy Green's functions, used in the above inversions, mainly based on radiative transfer
Use Qopen in Python scripts
To call Qopen from Python do e.g.:
from qopen import run run('go', conf='conf.json')
All configuration options in conf.json can be overwritten by keyword arguments passed to run().
Use Qopen to determine coda Q
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.
Use Qopen with coda normalization
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.
Get help and discuss
Please consult the API documentation.
The Obspy forum can be used to contact other users and developers. Please post the topic in the ObsPy Related Projects category.
Work through the extended Qopen tutorial.
A somewhat advanced example using the Qopen package: USAttenuation.
These studies make use of Qopen: Google Scholar Link.
Initial method: Sens-Schönfelder C and Wegler U (2006), Radiative transfer theory for estimation of the seismic moment, Geophysical Journal International, 167(3), 1363-1372, doi:10.1111/j.1365-246X.2006.03139.x
Enhanced Qopen method and implementation: Eulenfeld T and Wegler U (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]
Advanced example making use of alignment of site responses: Eulenfeld T and Wegler U (2017), Crustal intrinsic and scattering attenuation of high-frequency shear waves in the contiguous United States, Journal of Geophysical Research: Solid Earth, 122, doi:10.1002/2017JB014038 [pdf]
Robust source spectra using Qopen: Eulenfeld T, Dahm T, Heimann S, and Wegler U (2021), Fast and robust earthquake source spectra and moment magnitudes from envelope inversion, Bulletin of the Seismological Society of America, doi:10.1785/0120210200 [pdf]
Comparison between Qopen and MLTWA: van Laaten M, Eulenfeld T and Wegler U (2021), Comparison of Multiple Lapse Time Window Analysis and Qopen to determine intrinsic and scattering attenuation, Geophysical Journal International, 228(2), 913-926, doi: 10.1093/gji/ggab390 [pdf]
Comparison to inversion with the help of Mote-Carlo simulations based on elastic radiative transfer theory, relating g0 to g*: Gaebler PJ, Eulenfeld T and Wegler U (2015), Seismic scattering and absorption parameters in the W-Bohemia/Vogtland region from elastic and acoustic radiative transfer theory, Geophysical Journal International, 203(3), 1471-1481, doi:10.1093/gji/ggv393 [pdf]