Regional patterns of earthquake‐triggered landslides and their relation to ground motion

TLDR

The study aims to derive a landslide‑density expression analogous to seismic attenuation laws based on observed correlations between landslide density and ground acceleration. The authors formulate a general landslide‑density model and fit it to data from the Northridge, Chi‑Chi, and Ramu‑Markham earthquakes. They find that landslide density peaks where ground acceleration is strongest, decreases with distance, correlates linearly with peak ground acceleration, and that the derived model can generate shake maps from geomorphic data in uninstrumented regions.

Abstract

We have documented patterns of landsliding associated with large earthquakes on three thrust faults: the Northridge earthquake in California, Chi‐Chi earthquake in Taiwan, and two earthquakes on the Ramu‐Markham fault bounding the Finisterre Mountains of Papua New Guinea. In each case, landslide densities are shown to be greatest in the area of strongest ground acceleration and to decay with distance from the epicenter. In California and Taiwan, the density of co‐seismic landslides is linearly and highly correlated with both the vertical and horizontal components of measured peak ground acceleration. Based on this observation, we derive an expression for the spatial variation of landslide density analogous with regional seismic attenuation laws. In its general form, this expression applies to our three examples, and we determine best fit values for individual cases. Our findings open a window on the construction of shake maps from geomorphic observations for earthquakes in non‐instrumented regions.