Strain and Velocity Across the Great Basin Derived From 15-ka Fault Slip Rates: Implications for Continuous Deformation and Seismic Hazard in the Walker Lane, California-Nevada, USA

Abstract

Average strain across the Great Basin over the past 15 Kyr derived from slip rates on individual faults shows a concentration of both right-lateral shear and extension in the western Great Basin (Walker Lane). Straining is modest across the central Great Basin, with a zone of higher strain in the eastern Great Basin including the Wasatch Front. The horizontal velocity field derived from 15-ka fault slip rates is similar to the pattern of GPS velocities, suggesting that regional strain release patterns have been constant over the past 15 Kyr. The magnitudes of velocities inferred from fault slip rates, relative to North America, are lower than those from GPS in the Walker Lane, suggesting that the geologic record is missing evidence of strike slip on faults, and seismic hazard may be higher than suggested by fault slip rates alone. The observed strain concentration in the western Great Basin is consistent with a Sierra Nevada block that is more rigid than the surrounding lithosphere of nonlinear rheology, which concentrates strain east of and adjacent to the rigid block. Treating the western U.S. as a thin viscous sheet with the Sierra Nevada block as a rigid boundary provides a consistent history of continuous deformation in the Walker Lane over decadal, millennial, and Neogene timescales.