The Impact of Large Erosional Events and Transient Normal Stress Changes on the Seismicity of Fault
Résumé
The long‐term erosion of steep landscapes is punctuated by dramatic erosional events that can remove significant amount of sediments. Recent results in geomorphology suggest that the rivers can remove large volumes of landslide material within several years to decades, a time-scale much smaller than the seismic cycle. However, the role of such large erosional events on seismicity is poorly understood. In this study we use QDYN, a quasi‐dynamic numerical model of earthquake cycles to investigate the effect of a large erosional event on seismicity. The progressive evacuation of landslide sediments is modeled by a transient normal stress decrease. We show that erosional events with a shorter duration compared with the duration of a seismic cycle can significantly increase the seismicity rate, even for small stress changes. Moreover, large erosional events with a shorter period compared with the earthquake nucleation timescale can change earthquake size distribution by triggering more small events. Those results suggest that large erosional events can significantly affect seismicity, illustrating in turn the short‐term impact of surface processes on tectonics. They also suggest that such cumulative processes, including large erosional events, but also glacial melting, or human‐induced water extraction, can significantly contribute to the deformation of the crust at least in its shallow part.