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

人们对海底滑坡的动态知之甚少。虽然一些山体滑坡会迅速崩解，但其他山体滑坡可能会保持连贯的块状。最近，有人提出，海底滑坡也可能具有非常缓慢的(蠕动)变形的特征。新西兰东海岸的图埃尼滑坡复合体可能是研究这种缓慢滑动的山体滑坡的关键地点。我们建议通过所谓的P-CABLE系统收集滑坡体不同部分的三维地震数据。P-CABLE系统是一种低成本、低折叠、高分辨率的三维地震采集系统，可以部署在相对较小的船只上。该项目的船期将由我们的新西兰合作伙伴在调查船Tangaroa上提供。拟议项目的主要目标包括开发滑坡演化模型，调查工作区的甲烷水合物系统，特别强调其对滑坡动力学的作用，以及分析图埃尼滑坡复合体的变形方式。有两种相互矛盾的假说来解释这种变形方式：i)水合物阀意味着天然气水合物稳定带底部的超压在浅层天然气水合物带下方聚集，这导致了水压破裂并诱导了小规模的幕式活动。Ii)水合物-沉积物冰川假定了含天然气水合物沉积物的塑性行为，导致持续的下坡蠕动。众所周知，天然气水合物在短期变形过程中会增强沉积物，但尚不清楚它们在缓慢变形过程中是否会表现出类似于冰的塑性行为。虽然水合物阀假说得到了理论模型的支持，但最近的实验室实验支持水合物-沉积物冰川假说。三维地震数据将允许绘制变形指示图(挤压、伸展、剪切带、滑脱)，这将有助于区分蠕变和幕式滑动的运动学。拟议中的数据将是第一个慢饮海底滑坡的3D地震数据集。此外，这些数据将大大支持在IODP(综合海洋钻探计划)框架内以及在即将到来的RV Sonne巡航期间与机器人海底钻机Mebo一起计划的钻探活动。

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.