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Group B, Poster #056, Tectonic Geodesy

Understanding off-fault deformation in geodetic block models of southern California

Eileen L. Evans, & Jayson P. Sellars
Poster Image: 

Poster Presentation

2023 SCEC Annual Meeting, Poster #056, SCEC Contribution #13228 VIEW PDF
Determining fault slip rates throughout a complex fault system, such as the Pacific-North America plate boundary in southern California, is essential for understanding tectonic strain partitioning at the plate-boundary scale. However, the presence of off-fault or distributed deformation may lead to discrepancies between fault slip rates estimated from geologic observations (geologic slip rates) and those modeled from satellite geodetic measurements such as Global Navigation Satellite Systems (GNSS) (geodetic fault slip rates). Geodetic slip rates in a complex plate boundary may be estimated within kinematic block models, in which the crust is divided into rigid microplates bounded by faults,... and fault slip rates are determined by differential rotation rates at block boundaries. Because block models require that faults connect to form closed, rigid blocks, model faults must often be inferred or invented, limiting understanding of deformation away from mapped structures. Recent advances in block modeling allow the relatively rapid creation of suites of possible connections within a single fault system. We find that considering an ensemble of fault geometries and model regularization parameters leads to robust estimates of fault slip rates and model-based uncertainties, and highlights regions that require significant off-fault deformation (i.e., not on the original mapped faults).