Understanding slow-slipping submarine landslides: 3D seismic investigations of the Tuaheni landslide complex

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The dynamics of submarine landslides is only poorly understood. While some landslides rapidly disintegrate others may stay as coherent blocks. Recently, it has been proposed that submarine landslides could also be characterized by very slow (creeping) deformation. The Tuaheni landslide complex off the east coast of New Zealand may acts as key site for investigating such slow-slipping landslides. We propose to collect 3D-seismic data covering different parts of the slide complex by means of the so-called P-cable system. The P-cable system is a cost-efficient, low-fold, high resolution 3D-seismic acquisition system, which can be deployed on relatively small vessels. Ship time for this project will be provided by our New Zealand cooperation partners on the research vessel Tangaroa. Main objectives of the proposed project include the development of a model for landslide evolution, the investigation of the methane hydrate system in the working area with special emphasis on its role for landslide dynamics, and the analysis of the deformations style for the Tuaheni landslide complex. Two competing hypotheses have been postulated to explain the deformation style: i) The Hydrate Valve suggest build-up of overpressure at the base of the gas hydrate stability zone beneath a shallow gas hydrate zone, which causes hydro-fracturing and induces small scale episodic mobility. ii) The Hydrate-Sediment Glacier postulates plastic behavior of gas hydrate bearing sediments resulting in continuous downslope creep. Gas hydrates are known to strengthen sediments during short-term deformation but it is unclear whether they may exhibit plastic behavior during slow deformation, similar to ice.While the Hydrate Valve hypothesis is supported by theoretical models, recent laboratory experiments favor the hydrate-sediment glacier hypothesis. The 3D-seismic data will allow to map deformation indicators (compression, extension, shear zones, decollement) that will help distinguishing the kinematics of creep versus episodic slip. The proposed data would be the first 3D-seismic data set of a slow-sipping submarine landslide. In addition, the data will significantly support planned drilling activities in the frame of IODP (Integrated Ocean Drilling Program) and with the robotic seafloor drilling rig MeBo during an upcoming RV Sonne cruise.