Mapping basin-wide subaquatic slope failure susceptibility as a tool to assess regional seismic and tsunami hazards

Abstract

This study of subaquatic slope failures in Lake Lucerne, central Switzerland, presents a new concept for evaluating basin-wide slope stability through time as a potential tool for regional seismic and tsunami hazard assessments. Previously acquired high-resolution bathymetry and reflection seismic data, as well as sedimentological and in situ geotechnical data, provide a comprehensive data base to use this lake as a “model basin” to investigate subaquatic landslides and related geohazards. Available data are implemented into a basin-wide slope model. In a Geographic Information System (GIS)-framework, a pseudo-static limit equilibrium infinite slope stability equation is solved for each model point representing reconstructed slope conditions at different times in the past, during which earthquake-triggered landslides occurred. Comparison of reconstructed critical stability conditions with the known distribution of landslide deposits reveals minimum and maximum threshold conditions for slopes that failed or remained stable, respectively. The resulting correlations reveal good agreements and suggest that the slope stability model generally succeeds in reproducing past events. The basin-wide mapping of subaquatic slope failure susceptibility through time thus can also be considered as a promising paleoseismologic tool. Furthermore, it can be used to assess the present-day slope failure susceptibility, allowing for identification of location and estimation of size of future, potentially tsunamigenic subaquatic landslides.