Basin Sediments Geometry and Strength as Controls for Post-Failure Emplacement Style of Alpine Sub-Lacustrine Landslides

Abstract

Predicting the evolution of underwater mass movements in their post-failure stage is vital for risk assessment of offshore structures and ensuring safety of coastal communities threatened by tsunami waves. In the absence of sedimentological and geotechnical data, variability of the post-failure behavior in a specific marine or lacustrine setting is often attributed to predisposition factors such as the slope height-drop and depth to the basal shear surface. In this paper, the contribution of other geometrical parameters such as the slope inclination and the relative thickness of the frontal basin sediments is investigated using a coupled Eulerian-Lagrangian finite element framework. An emphasis is given to the important role of the strength difference between the slope and frontal basin sediments. The suggested framework is first validated against the well-documented Zinnen slide in Lake Lucerne (Switzerland), successfully reproducing the post-failure geometry and capturing the main features observed in published seismic profiles. It is then applied in a parametric study to illustrate the decisive role of the frontal basin sediments in determining the post-failure geometry of underwater mass wasting in similar settings.