A geologic block model of southern California

Eileen L. Evans, Abigail Travers, Jayson P. Sellars, Monica A. Diaz, & Jack P. Loveless

Submitted August 30, 2026, SCEC Contribution #15397, 2026 SCEC Annual Meeting Poster #TBD

Determining fault slip rates throughout a complex fault system, such as in southern California, is essential for understanding tectonic strain partitioning and seismic hazard at plate-boundary scales. Fault slip rates may be estimated using tectonic geomorphology and paleoseismology (geologic slip rates) or modeled from satellite geodetic measurements such as Global Navigation Satellite Systems (GNSS) (geodetic slip rates). Block models, in which the crust is divided into microplates bounded by faults, ensure kinematic consistency across a complex plate boundary. Typically, block models are constrained by interseismic GNSS velocities, possibly supplemented by geologic slip rate observations. Here we apply several novel innovations to the block modeling methodology to create a suite of fully geologic block models of the southern California fault system, in which geologic slip rates are the only constraints. We consider the full ensemble to estimate geologically-constrained slip rates and model-based uncertainties throughout the boundary. This approach allows us to identify geologic slip rates that may be inconsistent with overall plate boundary kinematics, and regions that may require additional fault slip or off-fault deformation. Furthermore, we find that geologic slip rates are systematically higher on the San Andreas and Garlock faults than geodetic slip rates estimated within a comparable block model ensemble, but that geodetic slip rate estimates are higher on minor faults.

Citation
Evans, E. L., Travers, A., Sellars, J. P., Diaz, M. A., & Loveless, J. P. (2026, 08). A geologic block model of southern California. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy