A physically based expression for the total volume and area of earthquake induced landsliding.

Abstract:

Earthquake impart a catastrophic forcing on hillslopes, that often lead to widespread landsliding and can contribute significantly to sedimentary and organic matter fluxes. We present a new expression for the total area and volume of populations of earthquake-induced landslides.This model builds on a set of scaling relationships between key parameters, such as landslide density, ground acceleration, fault size, earthquake source depth and seismic moment, derived from geomorphological and seismological observations. To assess the model we have assembled and normalized a catalogue of landslide inventories for 40 earthquakes. We have found that low landscape steepness systematically leads to over-prediction of the total area and volume of landslides.When this effect is accounted for, the model is able to predict within a factor of 2 the landslide areas and associated volumes for about two thirds of the cases in our databases. This is a significant improvement on a previously published empirical expression based only on earthquake moment.The prediction of total area is also sensitive to the landscape steepness, but less than the total volume.It seems also affected by the controls on the landslide frequency distribution that may include ground strength, soil continuity and extent or antecedent moisture. Some outliers in terms of observed landslide intensity are likely to be associated with exceptionally rock strength in the epicentral area, while others may be related to seismic source complexities ignored by the model.However, most cases in our catalogue seem to be relatively unaffected by these two effects despite the variety of lithologies and tectonic settings they cover.This makes our expression suitable for integration into landscape evolution models, and application to the assessment of secondary hazards and risks associated with earthquakes.