Poster #104, Tectonic Geodesy

Surface deformation nearby the Ridgecrest earthquakes: Frictional slip or compliant fault?

Xiaohua Xu, David T. Sandwell, Lauren A. Ward, Bridget R. Smith-Konter, Chris Milliner, Peng Fang, & Yehuda Bock
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Poster Presentation

2020 SCEC Annual Meeting, Poster #104, SCEC Contribution #10563
High resolution Interferometric Synthetic Aperture Radar observations reveal a large number of linear strain concentrations (or fractures) surrounding the 2019 Ridgecrest earthquake sequence; more than 80% had not been mapped previously. In this study, we document and analyze the displacement and width of ~170 of these fractures. While most fractures (109) are displaced in the direction of the prevailing tectonic stress (prograde), we find a large number (~60) of fractures that are displaced in the opposite (retrograde) direction. Comparing static stress change models to the fractures, we were able to determine that these surface fractures can largely be explained with static stress change f...rom the earthquake sequence, with most antithetic motions associated with compliant fault deformation, where most prograde fractures resulting from shallow frictional slip. We explain these observations with a model where the crust for the entire region is critically stressed prior to large earthquakes, thus forward frictional slip is relatively easy to trigger, while the amount of stress needed for these faults to achieve critical stress status acts as a buffer that resists backward frictional slip. A major implication of these findings is that much of the prograde tectonic strain is accommodated by inelastic deformation on many pre-existing faults.