A Preliminary 3D Mechanical Model of Central California Fault Slip Rates

Francisco Roland-Sagui, & Scott T. Marshall

Submitted August 30, 2026, SCEC Contribution #15180, 2026 SCEC Annual Meeting Poster #TBD

Central California contains a complex network of strike-slip and reverse faults that pose significant seismic hazard to local populations and their infrastructure. Compared to other regions in California, many of these faults are poorly studied and do not have any credible long-term slip rate estimates. We present results from a preliminary three-dimensional (3D) Boundary Element Method model of 114 faults building on the Devine et al. (2022) models. The model incorporates complex 3D faults based on the SCEC Community Fault Model version 7.0 (CFM 7.0) but have been remeshed for numerical accuracy. The model is driven by the Pacific-North American plate motion (50 mm/yr) and slip rates are kinematically applied to the San Andreas, Garlock, San Jacinto, Calaveras, Hayward-Rodgers Creek, and Berryessa/Bartlett Springs fault systems. The model calculates the full 3D slip distributions on all other modeled faults (114 in total) in response to both the plate motion and slip on the kinematically applied regional fault systems. To assess model performance, we compare model-calculated average slip rates to the Uniform California Earthquake Rupture Forecast, version 3, (UCERF3) geologic slip rate data. We find that 10/22 slip rates fall within the UCERF3 slip rate ranges with an overall RMSE of 0.58 mm/yr. Model-predicted slip rates along the fast-slipping San Gregorio and Hosgri faults agree well with the provided UCERF3 slip rates. Significant outliers include the Reliz and Monterey Bay-Tularcitos faults whose model-predicted slip rates are significantly faster than the measured UCERF3 rates. Because of the differences in dip angles and directions in many of the CFM 7.0 objects, many of which are poorly constrained, numerous faults intersect in the subsurface leading to unusual and discontinuous model-predicted slip at depth. Faults with potentially problematic subsurface intersections include the East Huasna, Nacimiento, Rinconada, Reliz, and Monterey Bay-Tularcitos faults. Future work will involve testing alternative but geologically plausible subsurface fault geometries for these faults. In the end, the model will provide full 3D slip rate distributions and average slip rates for 114 faults throughout central and southern California.

Key Words
Community Fault Model, Fault Slip Rates, Central California, Mechanical Model, Deformation

Citation
Roland-Sagui, F., & Marshall, S. T. (2026, 08). A Preliminary 3D Mechanical Model of Central California Fault Slip Rates. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)