Laboratory Simulations of Submarine Landslide Failure Mechanisms

Submarine slopes are subject to a variety of failure styles, ranging from large, long runout landslides to both shallow and deep-seated landslides with limited down-slope displacements. The upper continental slope off the east coast of the North Island of New Zealand, hosts numerous landslides which vary in size, volume and runout characteristics. The region is located on an active subduction zone experiencing regular earthquakes and is close to the base of gas hydrate stability. Consequently, both seismic loading during earthquakes and over-pressure in the slope from the migration of free gas may be plausible movement mechanisms for both shallow and deep landslides but their potential behaviour during earthquakes and in response to elevated pore fluid pressures remains poorly constrained. We conducted a series of experiments in a Dynamic Back Pressure Shearbox on sediments recovered from the Hikurangi subduction margin to simulate the complex stress conditions in submarine landslides and explore their potential movement mechanisms in response to elevated pore fluid pressures and seismic loading. Our experiments successfully simulated a range of landslide behaviour that advances our understanding of the variety of landslide types observed on active continental margins. The movement behaviours observed provide credible mechanisms to explain how some submarine landslides may be subject to episodic movement without undergoing catastrophic failure as a result of over pressuring by free gas and seismic loading during earthquakes.