Impact of long-term erosion on crustal stresses and seismicity in stable continental regions

Abstract

Abstract The causes of seismicity in stable continental regions (SCRs) remain an open question, in particular with respect to (1) the transient or steady-state nature of the forcing mechanisms and (2) the bias toward shallow seismicity. In this study, we test the impact of long-term localized erosion on crustal stresses and the promotion or inhibition of seismicity in SCRs. We subject numerical models with various geotherms and rheologies to typical SCR erosion rates (4–200 m/m.y.) over 10 m.y. to estimate the lithosphere mechanical response and the associated stress perturbations. In all models, the lithosphere deformation and stresses due to long-term localized erosion are close, but not identical, to those predicted by a simple elastic plate model. In specific cases with relatively high geotherm or weak crust, upper mantle or lower crust viscous flow can significantly impact the upper crust stress perturbations. Overall, erosion-induced horizontal tension is maximum in the upper crust (0–10 km depth) and much smaller in the mid- and lower crust. These stress perturbations reach a few tens of megapascals to a few megapascals over a few million years. Depending on the erosion patterns and regional state of stress, they can promote fault instability and seismicity for all faulting styles. Our results suggest that erosion-induced stresses can contribute to explaining the bias toward shallow seismicity in SCRs.