OpenSHA: New tools and file formats for building and analyzing UCERF3-style rupture sets and running inversions

Kevin R. Milner, & Edward H. Field

Published August 13, 2021, SCEC Contribution #11351, 2021 SCEC Annual Meeting Poster #029 (PDF)

The 3rd Uniform California Earthquake Rupture Forecast (UCERF3) model, released in 2014, introduced Fault System Rupture Sets and Solutions as data containers for fault-based earthquake rupture forecasts. A Rupture Set defines all of the on-fault supra-seismogenic (i.e., those that break the full seismogenic width of the fault, approximately M>6.5) ruptures in a Fault System, and their properties (magnitude, rake, etc). A Solution defines the annual rate of occurrence of each rupture, and may also supply information about gridded seismicity (off-fault and/or sub-seismogenic ruptures).

UCERF3 used binary file formats that were space-efficient, but difficult for end users to parse and modify. We are currently in the process of updating the legacy UCERF3 file formats to be more user friendly, for use with UCERF4 and the 2023 update to the U.S. National Seismic Hazard Model (NSHM). In this new format, core data are stored in simpler or standard file-formats including CSV and GeoJSON.

As part of this process, we are developing a series of command-line tools that can be used by individual investigators to build their own UCERF3-like models or to modify components of the California model (e.g., updating or adding faults for site-specific analysis and running an inversion). Users can specify their own set of faults in a GeoJSON format, split those fault sections into sub-sections, and use the UCERF3 (or preliminary UCERF4) algorithm to build a Rupture Set from the set of possible single- and multi-fault ruptures on those sub-sections. Then, users can run a simulated annealing inversion on their Rupture Set to generate a Solution, view various model diagnostics including regional and fault magnitude frequency distributions, and compute and disaggregate hazard curves at sites.

These tools and file-formats are currently in active development, and we plan the release of a preview version with limited capabilities to be available for community feedback. Stable versions of the tools will be available before release of the 2023 update to the U.S. NSHM.

Key Words
OpenSHA, UCERF3, UCERF4, Inversion, Hazard, PSHA, NSHM, NSHM23

Citation
Milner, K. R., & Field, E. H. (2021, 08). OpenSHA: New tools and file formats for building and analyzing UCERF3-style rupture sets and running inversions. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Computational Science (CS)