Mechanics of near-field deformation during co- and post-seismic shallow fault slip

Scientific Reports
By: , and 

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Abstract

Poor knowledge of how faults slip and distribute deformation in the shallow crust hinders efforts to mitigate hazards where faults increasingly intersect with the expanding global population at Earth’s surface. Here we analyze two study sites along the 2014 M 6.0 South Napa, California, earthquake rupture, each dominated by either co- or post-seismic shallow fault slip. We combine mobile laser scanning (MLS), active-source seismic tomography, and finite element modeling to investigate how deformation rate and mechanical properties of the shallow crust affect fault behavior. Despite four orders-of-magnitude difference in the rupture velocities, MLS-derived shear strain fields are remarkably similar at the two sites and suggest deceleration of the co-seismic rupture near Earth’s surface. Constrained by the MLS and seismic data, finite element models indicate shallow faulting is more sensitive to lithologic layering and plastic yielding than to the presence of fault compliant zones (i.e., regions surrounding faults with reduced stiffness). Although both elastic and elastoplastic models can reproduce the observed surface displacement fields within the uncertainty of MLS data, elastoplastic models likely provide the most reliable representations of subsurface fault behavior, as they produce geologically reasonable stress states and are consistent with field, geodetic, and seismological observations.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Mechanics of near-field deformation during co- and post-seismic shallow fault slip
Series title Scientific Reports
DOI 10.1038/s41598-020-61400-9
Volume 10
Year Published 2020
Language English
Publisher Springer Nature
Contributing office(s) Earthquake Science Center
Description 5031, 13 p.
Country United States
State California
Other Geospatial Napa Fault Zone
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