Environmental change, hydrate dissociation, and submarine slope failure along continental margins: the role of saturation anomalies in landslide triggering

Submarine landslides occur along active and passive continental margins and are potentially triggered by numerous factors including the dissociation of gas hydrates. The hazard produced by such landslides can damage infrastructure (oil platforms, telecommunication lines), generate tsunamis, and cause a catastrophic release of methane to the atmosphere and ocean. Here we develop numerical models to identify the conditions under which the dissociation of gas hydrates can trigger submarine landslides. We generate a steady state distribution of hydrates in a 1D sediment column and then dissociate these hydrates by perturbing the sea floor conditions (i.e. change in ocean bottom temperature or sea level). We focus on the dissociation of highconcentration hydrate anomalies (i.e. lenses and nodules) at fine to coarse-grained stratigraphic boundaries that are subject to large changes in sediment permeability and cohesion over small distances. Our numerical models track the evolution of the pore-water pressure as solid hydrate anomalies decay, which can induce rapid consolidation of the sediments, and also enhance fluid flow by modifying the average density of the pore fluids. We use an infinite-slope analysis as a prelude to development of a rate and state friction approximation to quantify whether these changes in pore-water pressure or cohesion can decrease the sediment strength enough to result in immediate slope failure, or bring the system closer to failure. Our results indicate that changes in effective stress ranging from kPa to MPa are required to trigger slope failure.