How Small Slip Surfaces Evolve Into Large Submarine Landslides—Insight From 3D Numerical Modeling

Submarine landslides are a major marine geohazard affecting resilience of offshore infrastructure and coastal urban centers. Attention has previously been paid to quantifying post-failure dynamics of catastrophic submarine debris flows and their consequences. However, pre-failure initiation and growth of a small slip surface evolving into a large submarine landslide are still less understood. This study aims to explore the physical failure mechanism of submarine landslides initiated from small slip surfaces and to quantify key features of failure evolution. They are achieved by modeling the entire three-dimensional (3D) landslide evolution, integrating the initiation and growth of slip surface, failure of slab above the slip surface, post-failure mass movement and re-deposition of transported sediments, using a novel numerical method. The characteristics of the slip surface growth within a favored layer and the patterns of the slab failure in the overlying layer have been thoroughly discussed. The transition from the pre-failure slip surface growth to the diverse post-failure mass movement are first observed and discussed with the 3D geometry effects, revealing the complex cascading mass movement mechanisms. The criterion for unstable growth of a planar slip surface and critical condition for slab failure are proposed. The findings from the study facilitate scientific understanding of the evolution of historic events and help safeguarding offshore developments against submarine landslide recurrence