Submarine landslides triggered by destabilization of high‐saturation hydrate anomalies. (3rd July 2017)

• Record Type: Journal Article
• Authors: Handwerger, Alexander L.; Rempel, Alan W.; Skarbek, Rob M.
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 18:Number 7(2017)
• Page Start: 2429
• Page End: 2445
• Publication Date: 2017-07-03
• Subjects: gas hydrates -- hydrate anomalies -- slope failure -- submarine landslides -- excess pore pressure -- rate and state friction; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1002/2016GC006706
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: Submarine landslides occur along continental margins at depths that often intersect the gas hydrate stability zone, prompting suggestions that slope stability may be affected by perturbations that arise from changes in hydrate stability. Here we develop a numerical model to identify the conditions under which the destabilization of hydrates results in slope failure. Specifically, we focus on high‐saturation hydrate anomalies at fine‐grained to coarse‐grained stratigraphic boundaries that can transmit bridging stresses that decrease the effective stress at sediment contacts and disrupt normal sediment consolidation. We evaluate slope stability before and after hydrate destabilization. Hydrate anomalies act to significantly increase the overall slope stability due to large increases in effective cohesion. However, when hydrate anomalies destabilize there is a loss of cohesion and increase in effective stress that causes the sediment grains to rapidly consolidate and generate pore pressures that can either trigger immediate slope failure or weaken the surrounding sediment until the pore pressure diffuses away. In cases where failure does not occur, the sediment can remain weakened for months. In cases where failure does occur, we quantify landslide dynamics using a rate and state frictional model and find that landslides can display either slow or dynamic (i.e., catastrophic) motion depending on the rate‐dependent properties, size of the stress perturbation, and the size of the slip patch relative to a critical nucleation length scale. Our results illustrate the fundamental mechanisms through which the destabilization of gas hydrates can pose a significant geohazard. Key Points: Hydrate anomalies increase effective cohesion and overall slope stability Destabilization of hydrate anomalies leads to rapid consolidation and excess pore pressures that can weaken sediment and trigger slope failure Landslide motion can be gradual or catastrophic depending on frictional properties and perturbation extent