Progressive Failure Cycles and Distributions of Earthquake-Triggered Landslides

Advances in the collection and analysis of landslide inventory data have allowed for greater understanding of spatial distributions of landslides triggered by earthquakes. However, current approaches to analysing and modelling these phenomena do not account for the response of the individual potential landslide masses and their temporally evolving stability. This stems, in part, from the lack of a conceptual model describing the effect of seismic waves on the strength and stability of hillslopes, which can be applied at the regional scale and over long (multiple earthquake) time scales. Here we present such a conceptual model linking weakening via progressive failure, inertial displacements driven by seismic ground accelerations, and the repeating failure of sections of hillslopes through time. We explore the implications of the model for how various characteristics of earthquake-triggered landslide distributions are interpreted and understood. These include the apparently stochastic nature of spatial landslide occurrence, spatial patterns of landsliding, landslide magnitude-frequency distributions, global variability in numbers of landslides triggered by earthquakes, and in particular why in any earthquake smaller areas of hillslope fail than do not, even in regions of apparently high landslide susceptibility. Finally, we also propose means of testing the validity of this model relative to alternative hypotheses.