Software to determine relative earthquake moment tensors
Installation of relMT is easy. The basic installation requires:
- The FFTW library (often provided via the system package manager)
- The Python packages NumPy, SciPy, PyYAML
Note
relMT is currently tested only on Linux systems.
Windows users, please use the Linux Subsystem for Windows (WSL) and proceed with the instructions below.
Mac users will need to install the fortran compiler
gfortranon your system. Please consult the Fortran documentation for details. Then proceed below.
This installation instruction assumes installation with Conda, pip and git. Experienced users may use uv or other tools instead.
As a pre-requisite, please install Miniconda.
We recommend to create a conda environment or to install into an existing one. Choose any Python version greater or equal 3.10
# Create and activate the environment
conda create -n relmt python
conda activate relmt
# Install the Fastest Fourier Transform in the West
conda install -c conda-forge fftwIf not already present, install pip
conda install pipIf not already present, install git
conda install gitNow install relMT locally
git clone https://github.com/wasjabloch/relMT
cd relMT
pip install .For plotting, we require:
- Matplotlib for all plotting
- networkx to visualize connections of equations in the linear system
- Pyrocko to plot moment tensors
Consider installing these packages using the plot optional dependency:
pip install .[plot]Some additional functionality requires community packages:
- Import of waveforms and station inventories via ObsPy
- Computation of spectra with Multitaper
- Conversion to and from Cartesian coordinates with UTM
Consider installing these packages using the extra optional dependency:
pip install .[extra]Note
Users experiencing problems installing ObsPy may temporarily need to pin setuptools below version 82
pip install "setuptools<82"
If you are working in IPython, or Jupyter, install the package in the same Conda environment to avoid version conflicts
conda install ipythonor
conda install jupyterIf you consider contributing to relMT, please install the development version
pip install .[dev]The documentation is hosted at: https://relmt.readthedocs.io/en/latest/
The algorithm consists of the following steps:
- Choose a cluster of seismic events for which the Green's function can be assumed equal
- Align P and S wave train observations to the sample
- At each seismic station, decompose the wave trains into principal components
- Measure relative P-wave and S-wave amplitudes
- Set up a linear system that relates relative amplitudes to moment tensors
- Solve the linear system using algebraic methods
The algorithms are based on the following research articles:
Dahm, T., J. Horalek, and J. Sileny (2000). Comparison of absolute and relative moment tensor solutions for the January 1997 West Bohemia Earthquake swarm. Studia Geophys. et Geod., https://doi.org/10.1023/A:1022166926987
Plourde, A. P., and M. G. Bostock (2019). Relative moment tensors and deep Yakutat seismicity, Geophys. J. Int., https://doi.org/10.1093/gji/ggz375
Bostock, M. G., A. P. Plourde, D. Drolet, and G. Littel (2021). Multichannel alignment of S waves, Bull. Seismol. Soc. Am., https://doi.org/10.1785/0120210076
Drolet, D., M. G. Bostock, A. P. Plourde, and C. G. Sammis (2022). Aftershock distributions, moment tensors and stress evolution of the 2016 Iniskin and 2018 Anchorage Mw 7.1 Alaskan intraslab earthquakes. Geophys. J. Int., https://doi.org/10.1093/gji/ggac165
Drolet, D., M.G. Bostock, and S. Peacock (2023). Relative Moment Tensor Inversion for Microseismicity: Application to Clustered Earthquakes in the Cascadia Forearc. Seismica. https://doi.org/10.26443/seismica.v2i4.1311
This software package is part of the relMT project that has received funding from the European Union’s Horizon Europe research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 101146483
