SKHASH

Python package for earthquake focal mechanism inversions.

Author: Robert Skoumal, U.S. Geological Survey | rskoumal@usgs.gov

This project contains Python code to compute focal mechanism solutions using first-motion polarities (traditional, consensus, and/or imputed) and S/P ratios (traditional and/or consensus).

How to Use

1. Install the latest release in your virtual environment:

# If you don't want to create beachball plots:
pip install -U SKHASH

# If you do want to create beachball plots:
pip install -U 'SKHASH[plot]'

Python 3.8+ versions are supported.

2. Run SKHASH with your desired control file:

SKHASH path_to/control_file.txt

More information

Running examples

A variety of examples are provided in the repository. It's recommended you play around with these examples to learn about some of the features.

1. Download the examples folder available HERE.
2. Unzip the folder.
3. Navigate to the examples folder you just downloaded, e.g.: cd examples
4. Run SKHASH with the example of your choice, e.g.: SKHASH hash1/control_file.txt

Manual

Refer to the manual or the wiki for additional information about running the code.

Fortran subroutine (completely optional)

By default, SKHASH will compute mechanisms using the Python routine. However, to speed up the grid search, you can choose to take advantage of an included Fortran subroutine. If the Python C/API wrapper does not already exist, SKHASH will automatically create the wrapper with the user's permission when the Fortran subroutine is used.

To use this Fortran routine, add the following lines to your control file:

$use_fortran
True

A fortran compiler will be needed on the user's machine. If one does not exist, here are some examples on how to get one:

# macOS Homebrew example
brew install gcc

# Ubuntu example
apt install gfortran

If you're using Python 3.12+, the meson and ninja packages are also needed.

pip3 install meson ninja

Note that if you are using macOS and receive an error, you may be missing the Command Line Tools package. To install:

xcode-select --install

Citation

Please cite our paper if you use anything in this project:

• Skoumal, R.J., Hardebeck, J.L., Shearer, P.M. (2024). SKHASH: A Python package for computing earthquake focal mechanisms. Seismological Research Letters, 95(4), 2519-2526. https://doi.org/10.1785/0220230329

Significant portions of this algorithm are based on HASH:

• Hardebeck, J.L., & Shearer, P.M. (2002). A new method for determining first-motion focal mechanisms. Bulletin of the Seismological Society of America, 92(6), 2264-2276. https://doi.org/10.1785/0120010200

• Hardebeck, J.L., & Shearer, P.M. (2003). Using S/P amplitude ratios to constrain the focal mechanisms of small earthquakes. Bulletin of the Seismological Society of America, 93(6), 2434-2444. https://doi.org/10.1785/0120020236

License and Disclaimer

License: This project is in the public domain.

Disclaimer: This software is preliminary or provisional and is subject to revision.