Impact of material properties on Bay Area rupture dynamics

Ritwik Patil, & Elizabeth H. Madden

Submitted September 7, 2025, SCEC Contribution #14825, 2025 SCEC Annual Meeting Poster #TBD

Northern California’s Bay Area lies along the Pacific North American plate boundary, placing millions of residents at risk from seismic activity. To assess rupture dynamics of the region, we constructed a high-resolution, 3D structural model and tetrahedral mesh of the Rodgers Creek, Hayward, Calaveras, and Northern Calaveras faults using fault traces from the National Seismic Hazard Model and incorporated topographic elevation from the USGS 3D Elevation Program. The Rodgers Creek fault extends 45 km north of Santa Rosa and the Calaveras fault 65 km south of Gilroy to its junction with the San Andreas fault, resulting in a mesh of roughly 10 million elements at an average edge length of 250 m on the faults.

We use SeisSol, an open-source, high-performance finite-element tool implementing the Arbitrarily high-order DERivative Discontinuous Galerkin (ADER-DG) scheme, to simulate earthquake rupture and seismic wave propagation. Each simulation is initialized with a static stress field and rupture is nucleated at different locations across multiple runs to assess variability in onset. Material properties, including density, P-wave velocity, S-wave velocity, and P- and S-wave attenuation, are extracted from the USGS 3D seismic velocity model for the San Francisco Bay region and imported via NetCDF grids. Fault failure is governed by a linear slip weakening friction law.

We compare elastically heterogeneous and homogeneous material scenarios, quantifying how realistic velocity values impact rupture arrival on the branched fault system, peak slip rates, and rupture speed. We also investigate the influence of multiple nucleation locations on rupture scenarios. Spatial and temporal patterns of slip, peak slip rate, and rupture velocity along each fault trace are analyzed to isolate the influence of geometry and material heterogeneity on rupture evolution.

Key Words
SeisSol, material heterogeneity, rupture dynamics

Citation
Patil, R., & Madden, E. H. (2025, 09). Impact of material properties on Bay Area rupture dynamics. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)