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Widespread rock damage from the 2019 Ridgecrest earthquakes

Alba M. Rodriguez Padilla, Michael E. Oskin, Chris Milliner, & Andreas Plesch

Accepted April 28, 2021, SCEC Contribution #10995

Inelastic processes from earthquakes contribute to the formation of fault damage zones that constitute a permanent sink of strain energy, modify the elastic properties of the shallow crust, and amplify near-field ground shaking. Constraints on the extent of inelastic deformation differ depending on the dataset and methodology used. We combine high-resolution fracture, strain, and aftershock maps from the 2019 Ridgecrest earthquakes to reconcile the properties of damage zones across different spatial scales and resolutions. The decay of inelastic deformation with distance away from the fault is well-described by an inverse power-law with exponent ~1.3, extends beyond ~20km away from the primary rupture, and is insensitive to lithology and rupture directivity. Based on our fracture density decay, we predict a decrease in shear modulus by ~40% immediately adjacent to the fault declining to <1% at 100 m. While deformation is focused on the zone of rigidity decrease, the damage decay is continuous without breaks in scaling, suggesting a single mechanism dominates yielding. Our results suggest that, in the long term, the crust behaves as a widely damaged volume that is permanently deformed and weakened by inelastic contributions from each earthquake.

Rodriguez Padilla, A. M., Oskin, M. E., Milliner, C., & Plesch, A. (2021). Widespread rock damage from the 2019 Ridgecrest earthquakes. Nature Geoscience, (accepted).

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)