Landslide patterns reveal the sources of large earthquakes

Abstract

The distribution of fault slip in an earthquake controls seismic surface deformation and ground shaking, and is the most direct record of fault response to tectonic stress. Detailed information about slip patterns in large earthquakes is only available where a dense local network of seismometers is in place. Elsewhere, the evaluation of earthquake source and mechanism relies on observation of proxies such as surface change or damage intensity. In upland areas the density of seismically induced landslides is strongly influenced by the intensity and duration of strong ground motion, and therefore contains information about the earthquake source mechanism. Here we show that density patterns of co-seismic landslides closely track the distribution of fault slip in two large thrust earthquakes in Japan. When adjusted for site effects, landslide distributions readily obtained from remote sensed images can supplement or replace instrumental records of earthquakes, opening historical and remote events for close geophysical investigation.