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3-D Seismic Characterization of Submarine Landslides on a Pliocene-Pleistocene Siliciclastic Continental Slope, South China Sea

Mangzheng Zhu1, Stephan Graham1, and Timothy McHargue2
1 Stanford University, Stanford, CA
2 ChevronTexaco, San Ramon, CA

Understanding submarine landslides is of great importance to both academic and industrial communities. A high-quality industry 3-D reflection seismic survey from the northern margin of the Qiongdongnan-Yinggehai basin of the South China Sea reveals a series of Pliocene-Pleistocene siliciclastic submarine landslide deposits, and clarifies the external morphology and internal seismic facies of these landslides. The three seismic elements of the submarine landslides in this area include a rupture surface, a displaced mass of sediments, and an upper landslide surface. Landslide evolutionary stages include pre-failure, failure and post-failure stages. In a seaward direction, these landslide deposits stack and offlap, whereas parallel to the margin they accumulate in a laterally compensatory fashion; over time, these processes summed to build the distal deltaic continental margin. The submarine landslides decreased in their extent and volume with time. Significantly inclined sea floor and high sedimentation rate set the stage for repetitive slope failure, and seismicity, high-frequency sea level changes and gas hydrate release perhaps were triggering mechanisms.