Frontal emplacement and mobility of sublacustrine landslides: Results from morphometric and seismostratigraphic analysis

Abstract

The morphometric characteristics of 96 sublacustrine landslide complexes were measured on dense grids of high-resolution seismic reflection data from several lakes worldwide and were statistically analyzed. This analysis reveals that the morphology of the sublacustrine slopes exerts a strong control on the size of slope failures that occur on them, as the location of the headscarp and frontal ramp of these landslides are mainly determined by changes in the slope gradient. Our dataset also shows that the height drop of the failing slope section and the subsurface depth of the basal shear surface are the main parameters that determine whether a landslide will propagate in a frontally confined or frontally emergent manner. These parameters respectively represent the gravitational potential energy (driving force) of the sliding mass and the potential energy required (a resisting force) for it to emerge at its frontal ramp. These observations open perspectives for predicting the frontal emplacement style of future sublacustrine and submarine landslides and their associated natural hazards (e.g., tsunamis, dense flows). Although the investigated sublacustrine landslides have smaller dimensions than most submarine landslides, our data reveal mostly comparable inter-parameter correlations and relationships. However, frontally emergent landslides in lakes (and fjords) generally have a larger mobility and underwent a larger disintegration than what would have been expected by extrapolation of empirical relationships derived for ocean margin landslide datasets. This can be explained by the highly-unconsolidated material usually involved in the shallowly excavated slope failures in lakes and fjords.