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GA W-Phase

Software used for running wphase moment tensor + centroid inversions in the National Earthquake Alert Centre at Geoscience Australia.

Originally implemented by Roberto Benavente.

Based on the paper Source inversion of W phase: speeding up seismic tsunami warning by Kanamori and Rivera, 2008

Requirements

  • Python 2.7+ or 3.6+ (with various PyPI dependencies)
  • Green's functions (see the section below)
  • Optional:
    • SeisComP with python libraries (to use the CLI script to push results into a SeisComP system/convert results to SCML)

Green's Functions

The Green's Function database used for W-Phase at GA is the same as those used by Kanamori and Rivera in their original implementation - see here for their information regarding these. You can contact them to attempt to obtain a copy of their original database; or attempt to generate a new one yourself using the PREM model. The database is stored as a directory structure containing SAC files, following this template:

H{DEPTH}/{MT_COMPONENT}/GF.{DISTANCE}.SY.LH{C}.SAC

Where:

  • DEPTH is the depth in km, which must end in .5
  • MT_COMPONENT is the moment tensor component, one of PP, RP, RR, RT, TP, TT where P is φ, T is θ, R is r.
  • DISTANCE is the distance in 10ths of a degree, padded to 4 characters. (In the current implementation, your database must include every 10th of a degree from 0 to 90 degrees.)
  • C is the waveform component

For example, the vertical (Z) Green's function for Mφφ=1 (PP) at a depth of 500.5km and distance of 90 degrees is stored at H500.5/PP/GF.0900.SY.LHZ.SAC.

As alternative to this very large file structure, an equivalent structure can be stored inside a HDF5 file.

Direct Installation

From the same directory this README lives in:

pip install .

If you want to use it 'in place', use develop mode:

pip install -e .

If obspy has issues installing, you might need to install some dependencies first:

pip install wheel Cython numpy
pip install .

Running wphase

Required environment variables:

  • WPHASE_OUTPUT_DIR: absolute path to a directory in which W-Phase will write its outputs.
  • WPHASE_GREENS_FUNCTIONS: absolute path to greens functions (either a directory or a hdf5 file, as described above)

You can then run W-Phase in a couple of ways:

  • Directly from python, with basic results returned in a nested dict and visualizations written to a provided output directory. See e.g. test_runwphase for a minimal example.

  • Using the command-line script wphase, which takes its input as (a lot of!) command-line arguments and can send the basic results directly to a SeisComP messaging system, and the visualizations to an Amazon S3 bucket.

    For example, if you have an FDSN server at http://localhost:8081 and a SeisComP4+ messaging system at localhost:18180, the following script would attempt to solve for the centroid moment tensor of an event at the given location and time, and if successful, send the results to seiscomp under the given event ID.

wphase \
    --evid ga2020yskxhe \
    --lat 5.2 \
    --lon 125.47 \
    --depth 42 \
    --time '2020-12-15T23:22:01Z' \
    --outputs /tmp/wphase-outputs \
    --server http://localhost:8081 \
    --host localhost:18180 \
    --debug

All the usual seiscomp configuration flags are available:

  • --console=1 to see errors on the command line (otherwise they are only written to the logfile!)
  • --debug to see all log messages on the command line
  • --user to set the messaging username (default is gawphase)
  • -g to set the primary messaging group on which results are sent (default is FOCMECH)

You can get a full list of options by invoking run-wphase with --help.

Using Docker

If you're running Linux with Docker and curl installed, you should be able to build a docker container simply by running (as root) ./run-or-build-container.sh build.

By default, the image is configured to run as a non-root user with uid 1000; hopefully this maps on to your host user for easy development. To change this uid (or gid), provide the build-args DOCKER_USER_UID and/or DOCKER_USER_GID.

Developing on Docker

While the container image includes the complete W-Phase application, it can easily be used for development by mounting in your working copy of the W-Phase source.

When you launch an interactive bash session on the container (e.g. using the run-or-build-container.sh script), if wphase is mounted at /wphase then it will be automatically built and installed in development mode.

This is done for you if you use ./run-or-build-container.sh run.

To use this script as-is, you'll need your greens functions to be stored at ~/wphase/greens; but you should be able to modify the script to suit your needs.

To start some process inside the container:

./run-or-build-container.sh run <command>

# for example, to start a bash shell:
./run-or-build-container.sh run bash

# to run the test suite:
./run-or-build-container.sh run pytest

# to run the same example as above:
./run-or-build-container.sh run wphase \
    --evid ga2020yskxhe \
    --lat 5.2 \
    --lon 125.47 \
    --depth 42 \
    --time '2020-12-15T23:22:01Z' \
    --outputs /tmp/wphase-outputs \
    --server http://localhost:8081 \
    --host localhost:18180 \
    --debug

Since the ./run-or-build-container.sh script uses host networking, this last example would still be able to contact the FDSN and Spread servers running on your host. Alternatively, you could of course use some other Docker networking scheme and swap out localhost for an appropriate hostname or IP.

Using Docker in production

The container image is also ready for production use: it includes a fully-built version of wphase and directly invokes the wphase script as its default entrypoint default. It does not include the greens functions database (since these are typically huge), so you'll still need to mount these; and you'll also need to mount a directory to /outputs, where the output files will be stored.

You can use the run-wphase directive to invoke the production container, automatically handling the directory mounting:

# to run the same example as above:
./run-or-build-container.sh run-wphase \
    --evid ga2020yskxhe \
    --lat 5.2 \
    --lon 125.47 \
    --depth 42 \
    --time '2020-12-15T23:22:01Z' \
    --server http://localhost:8081 \
    --host localhost:18180

In this example, the output files would then be available at ./outputs/ga2020ykxhe/.

TODO

I extracted this code from our private repository and ran a quick clean-up pass, but many more improvements are possible:

  • Improve the Python API to return the results (focal mech, derived origin, etc) in ObsPy or SeisComP data structures instead of the current nested dictionaries?
  • Look into replacing the libtau fortran code with obspy's travel time model.
    • When this code was first developed, apparently the latter was too slow; but things might have improved or there might be optimizations we can make.
    • I think this would allows us to relicense under the more permissive Apache license (GA's preference).
  • General refactoring and code cleanup. I've done some, but there is a lot left to do (particularly in the psi/ directory).
  • Create a fully-integrated SeisComP plugin/daemon that watches the messaging bus for events matching certain criteria and runs automatically (like scautomt does).

License

Copyright (C) 2021 Geoscience Australia

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.