Robust Imaging of Fault Slip Rates in the Walker Lane and Western Great Basin From GPS Data Using a Multi‐Block Model Approach.

The Walker Lane (WL) in the western Great Basin (GB) is an active plate boundary system accommodating 10%–20% of the relative tectonic motion between the Pacific and North American plates. Its neotectonic framework is structurally complex, having hundreds of faults with various strikes, rakes, and crustal blocks with vertical axis rotation. Faults slip rates are key parameters needed to quantify seismic hazard in such tectonically active plate boundaries but modeling them in complex areas like the WL and GB is challenging. We present a new modeling strategy for estimating fault slip rates in complex zones of active crustal deformation using data from GPS networks. The technique does not rely on prior estimates of slip rates from geologic studies, and only uses data on the surface trace location, dip, and rake. The iterative framework generates large numbers of block models algorithmically from the fault database to obtain many estimates of slip rates for each fault. This reduces bias from subjective choices about how discontinuous faults connect and interact to accommodate strain. Each model iteration differs slightly in block boundary configuration, but all models honor geodetic and fault data, regularization, and are kinematically self‐consistent. The approach provides several advantages over bespoke models, including insensitivity to outlier data, realistic uncertainties, explicit mapping of off‐fault deformation, and slip rates that are more objective and independent of geologic slip rates. Comparisons to the U.S. National Seismic Hazard Model indicate that ∼80% of our geodetic slip rates agree with their geologic slip rates to within uncertainties. Plain Language Summary: The Walker Lane (WL) is a complex zone of faults in the western Great Basin of the western United States that experiences frequent earthquakes driven by active plate tectonics. Ground networks of very sensitive GPS stations deployed over the last few decades have collected data showing where the ground deforms most quickly, and hence where earthquakes are more likely to occur. Data on how fast faults slip over time is used to inform the public about the distribution and intensity of the seismic hazard. In this study we present improved data and modeling that resolve with unprecedented detail the rates, patterns, and styles of active crustal motion, resulting in better estimates of fault slip rates in the WL. This work brings the picture of earthquake potential derived from GPS networks into sharper focus, provides new information about how plate tectonics works, and will lead to more accurate estimates of seismic hazard that can help reduce the loss of life and property from earthquakes. Key Points: We estimate Walker Lane fault slip rates using a dense filtered and gridded geodetic velocity field and a robust multi‐block model approachThe geodetic slip rates are independent of geologic slip rates, but 80% agree with them to within uncertaintiesThe method images off‐fault deformation and vertical axis rotations providing more insight into how crustal motion drives earthquakes [ABSTRACT FROM AUTHOR]