海域沉积物蠕动地貌的研究现状与展望

Review and Prospect of the Geomorphology of Sediment Creep in Sea Areas

沉积物蠕动是海底地层倾于发生破坏的前奏和指示,能够演变为大规模的海底滑坡,给海洋工程建设和人类生命安全带来巨大的威胁。目前发现的沉积物蠕动地貌主要发育在北半球,表现为槽脊相间的海底起伏。沉积物蠕动地貌的主要识别标志为槽脊形态的无规律变化与走向沿水深线延伸且槽脊内部发育剪切面等。地震活动、构造抬升、高沉积速率和地层压力、地层的含气性与水合物分解等均可导致沉积物蠕动地貌的形成。然而,在前人的研究过程中发现了诸多疑似沉积物蠕动地貌的起伏地形,证明或证伪这些起伏地形是否为沉积物蠕动地貌是目前研究的侧重点。沉积物蠕动的滑移变形速率、蠕动地层底界面及其与下伏构造的关系性、沉积物蠕动的形成过程和演变趋势等研究工作有助于进一步厘定沉积物蠕动地貌及其致灾等级,但这些工作还鲜有涉及。因此,后续沉积物蠕动地貌的研究应加强沉积物蠕动层底界面的刻画与表征,重视沉积物蠕动形成过程和演变趋势的数值模拟和物理模拟研究,为深入识别沉积物蠕动和评价其灾害等级提供重要的依据。

Sediment creep as the precursor and indicator of the destruction of the submarine stratum,which can evolve into a large-scale submarine landslide,poses a huge threat to marine engineering construction and human life safety. Sediment creep morphology is mainly found to develop in the northern hemisphere through literature sorting,which is manifested by seafloor undulations composed of troughs and ridges. The main identification marks of sediment creep morphology are irregular changes in the morphology of troughs and ridges and their strikes extend along the water depth line and shear planes offset the troughs and ridges. Seismic activity,structural uplift,high deposition rate and formation pressure,gas-bearing formation and hydrate decomposition,etc.,can all lead to the occurrence of sediment creep. However,many seafloor undulations suspected of sediment creep have been discovered in the process of previous research. The majority current research focuses on how to prove or falsify if these seafloor undulations are sediment creep. The slip deformation rate and the bottom interface of creep and its relationship with the underlying structure,the study of the formation process and evolution trend of sediment creep,etc.,help to further determine the sediment creep,but its disaster evaluation work is rarely involved. Therefore, subsequent studies on sediment creep should strengthen the delineation and characterization of the bottom interface of sediment creep,and pay attention to the numerical and physical simulation studies of the formation process and evolution trend of sediment creep,which could contribute to the deep understanding of sediment creep and provide important information for evaluation of its disaster level.