Skip to main content
U.S. flag

An official website of the United States government

A comprehensive fault system inversion approach: Methods and application to NSHM23

December 22, 2023

We present updated inversion‐based fault‐system solutions for the 2023 update to the National Seismic Hazard Model (NSHM23), standardizing earthquake rate model calculations on crustal faults across the western United States. We build upon the inversion methodology used in the Third Uniform California Earthquake Rupture Forecast (UCERF3) to solve for time‐independent rates of earthquakes in an interconnected fault system. The updated model explicitly maps out a wide range of fault recurrence and segmentation behavior (epistemic uncertainty), more completely exploring the solution space of viable models beyond those of UCERF3. We also improve the simulated annealing implementation, greatly increasing computational efficiency (and thus inversion convergence), and introduce an adaptive constraint weight calculation algorithm that helps to mediate between competing constraints. Hazard calculations show that ingredient changes (especially fault and deformation models) are the primary driver of hazard changes between NSHM23 and UCERF3. Updates to the inversion methodology are also consequential near faults in which the slip rate in UCERF3 was poorly fit or was satisfied primarily using large multifault ruptures that are now restricted by explicit b‐value and segmentation constraints.

Publication Year 2024
Title A comprehensive fault system inversion approach: Methods and application to NSHM23
DOI 10.1785/0120230122
Authors Kevin R. Milner, Edward H. Field
Publication Type Article
Publication Subtype Journal Article
Series Title Bulletin of the Seismological Society of America
Index ID 70251122
Record Source USGS Publications Warehouse
USGS Organization Geologic Hazards Science Center - Seismology / Geomagnetism