pySATSI: A Python package for computing stress tensor inversions

Rob Skoumal, Jeanne L. Hardebeck, & Andrew J. Michael

Published September 8, 2024, SCEC Contribution #13871, 2024 SCEC Annual Meeting Poster #041

We introduce a Python package for computing focal mechanism stress inversions. This algorithm is based on the Spatial And Temporal Stress Inversion (SATSI) algorithm, originally written in C and Perl, with improvements to the capabilities, performance, and ease of use. Our algorithm introduces the ability to create non-uniform spatiotemporal grids using a variety of approaches, including a quadtree-inspired data structure. When some information is known about which nodal planes represent the fault planes, uncertainties can now be considered individually for each mechanism in the catalog. pySATSI can compute stress inversions more than an order of magnitude faster than SATSI, and additional runtime improvements can be obtained by using the option to parallelize uncertainty computations. Our algorithm is designed to handle a variety of input formats, including directly reading focal mechanism solutions computed from the SKHASH focal mechanism inversion software package. To demonstrate these new capabilities and features of pySATSI, we use it to compute stress tensors using a non-uniform spatial grid considering ~50,000 focal mechanism solutions previously computed in Southern California.

Key Words
focal mechanism, stress inversion

Citation
Skoumal, R., Hardebeck, J. L., & Michael, A. J. (2024, 09). pySATSI: A Python package for computing stress tensor inversions. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology