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

TL;DR

Large erosional events can significantly increase seismic activity and alter earthquake size distribution by inducing transient normal stress decreases, highlighting the short-term influence of surface erosion on fault seismicity.

Contribution

This study introduces a numerical model to quantify how large erosional events impact seismicity and earthquake size distribution through transient stress changes.

Findings

Erosional events with shorter durations than seismic cycles increase seismicity rates.

Large erosional events can trigger more small earthquakes.

Surface erosion has a significant short-term effect on fault seismicity.

Abstract

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 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 time-scale 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.