The Impact of Large Erosional Events and Transient Normal Stress Changes on the Seismicity of Faults

The long-term erosion of steep landscapes is punctuated by dramatic erosional events that can remove significant amount of sediments within a time-scale shorter than a seismic cycle. However, the role of such large erosional events on seismicity is poorly understood. 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 modelled by a transient normal stress decrease. We show that erosional events faster than a seismic cycle can significantly increase the seismicity rate, even for small normal stress changes. Moreover, large erosional events faster than the earthquake nucleation time-scale can change earthquake size distribution, by increasing the proportion of small events during the erosional period. Those results suggest that large erosional events can significantly affect seismicity, at least in the shallow portion of the crust.