Shallow Rupture Propagation of Pleistocene Earthquakes Along the Hurricane Fault, UT, Revealed by Hematite (U‐Th)/He Thermochronometry and Textures

Abstract

The shallow portions of fault zones accommodate the up-dip propagation of earthquake ruptures (Scholz, 2002). Forecasting earthquake hazards requires knowledge of slip distribution and the mechanical behavior of the shallow crust (Field et al., 2013;Nevitt et al., 2020;Petersen et al., 2015). Models for fault strength and predictions of rate-dependent frictional behavior with depth often depict the upper 3 km as an unconsolidated gouge or a voluminous bedrock zone(s) undergoing distributed deformation (e.g., Fagereng & Toy, 2011;Klinger et al., 2018;Sibson, 1983). Geodetic measurements indicate that a seismic slip deficit in the shallow crust may be explained by compliant zones of reduced elastic stiffness (Barbot et al., 2008) or elastoplasticity in off-fault damage zones (Kaneko & Fialko, 2011;Roten et al., 2017). However, fault growth, evolution, and structural maturity cause localization of on-fault deformation rather than creation of off-fault damage (Dolan & Haravitch, 2014). Paleoseismic trenches (Rockwell & Ben-Zion, 2007) and exhumed bedrock fault surfaces indicate deformation is localized even in the shallowest crust, and that structures are reactivated during recurring seismic events.