Accrual of widespread rock damage from the 2019 Ridgecrest earthquakes

Abstract

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. Here we combine 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 from the fault is well described by an inverse power law, extends beyond 20 km from the faults and is insensitive to lithology and slip magnitude. The damage decay is continuous without breaks in scaling, suggesting that a single mechanism dominates yielding. On the basis of our fracture density distribution, we predict an average reduction in shear rigidity of about 20% in bedrock and 40% in alluvium immediately adjacent to the fault, declining to less than 1% at 100 m. Our observations reveal how macroscopic fracturing generates intense near-fault damage and that widespread damage accrues regionally over multiple earthquake cycles.