A geologic block model of the western continental United States

Eileen L. Evans, & Abigail C. Travers

Published September 8, 2024, SCEC Contribution #13746, 2024 SCEC Annual Meeting Poster #083

The distribution of strain across the western Continental United States (WCUS) may be described in terms of long-term slip rates on faults within the Pacific-North America plate boundary. Estimates of fault slip rate can be made directly at points along a fault using tectonic geology (geologic slip rates), or modeled based on satellite-based 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. Here we apply several novel innovations to the block modeling methodology to create a fully geologic block model of the WCUS, in which geologic slip rates are the only constraints. We generate a suite of block geometries based on mapped faults and apply a range of model regularization parameters. We consider the full ensemble to estimate geology-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 WCUS kinematics, and identify regions that may require additional fault slip. For example, as a consequence of kinematic consistency, we estimate significant slip on the offshore San Clemente fault. Finally, we compare the geologic block models with geodetically constrained block models for a self-consistent comparison of geologic and geodetic fault slip rates.

Citation
Evans, E. L., & Travers, A. C. (2024, 09). A geologic block model of the western continental United States. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy