A numerical investigation of sediment destructuring as a potential globally widespread trigger for large submarine landslides on low gradients

Abstract

Submarine landslides on open continental slopes can be far larger than any slope failure on land and occur in locations worldwide on gradients of <2ı. Significantly elevated pore pressure is necessary to overcome the sediment’s shearing resistance on such remarkably low gradients, but the processes causing such overpressure generation are contentious, especially in areas with slow sedimentation rates. Here we propose that the progressive loss of interparticle bonding and fabric could cause such high excess pore pressure. Slow sedimentation may favour the formation of a structural framework in the sediment that is load-bearing until yield stress is reached. The bonds then break down, causing an abrupt porosity decrease and consequently overpressure as pore fluid cannot escape sufficiently rapidly. To test this hypothesis, we implement such a loss of structure into a 2D fully coupled stress-fluid flow Finite Elementmodel of a submerged low angle slope, and simulate consolidation due to slow sedimentation. The results suggest that destructuring could indeed be a critical process for submarine slope stability.