Seismic Characteristics And Trigger Mechanisms Of Submarine Landslides In Northern South China Sea

Submarine landslides, namely Mass transport deoposits (MTDs), are one kind ofsediment transportation that widely occur on the outer shelf/slope due to gravitationalinstability. The main mass transport processes consist of slide, slump and debris flow.Submarine landslides are widely developed in passive and active continental marginsand are an important part of Shelf-Slope system. Gas hydrates and oil/gas resourcesare rich in northern South China Sea. The geological setting in the shallow water areais relatively simple and has little potential to develop seabed geological disasters, solittle attention is paid on this area. However, the geological setting in the deep waterarea is much complex, the safety problems come from the drilling for deepwater oiland gas have become a hinder for deepwater oil and gas development in South ChinaSea. So the research of distribution and trigger mechanisms of submarine landslides inthe northern South China Sea is significant for the future safety assessment of theoil/gas exploration in South China Sea.In this paper, based on interpretation of multi-beam bathymetry data,2D and3Dseismic data in the northern South China Sea, and combine with sequence stratigraphyanalysis and geophysical property analysis, we study the submarine landslides in thedeepwater area of northern South China Sea and identify numerous submarinelandslides in the central Canyon of Qiongdongnan Basin and Pearl River MouthBasin.For the purposes of the present study we group the various kinematic indicatorsaccording to the domain in which they are most likely to occur within a submarinelandslide and divide it into three different units: the headwall domain, translationaldomain and the toe domain and different unit has different seismic characteristics. Thesubmarine landslides developed in Qiongdongnan Basin are mainly distributed in thecentral Canyon with small size and high frequency. The submarine landslides alsoplay an vital role in canyon fill after the formation of central Canyon. Highsedimentation rates, earthquake, sea level change and seabed terrain slope changecaused by tectonic movement are considered as the potential trigger mechanisms ofsubmarine landslides in central Canyon. Furthermore, the high sedimentation ratesand activities of Honghe strike-slip fault might be the main reasons. The Baiyun Slideidentified in Pearl River Mouth Basin is mainly distributed in the Baiyun Sag andaffects an area of10000km2which makes it one of the largest submarine slides innorthern South China Sea. Fluid flow systems including tectonic fault, gas chimney,polygonal faults and so on are widely developed in the area affected by Baiyun Slidewhich imply active fluid flow in this area that provides a overpressure environmentfor the formation of Baiyun Slide. Besides, gas hydrates might be distributed in theheadwall area of Baiyun Slide and the formation and decomposition of gas hydratesmight lead to the formation of Baiyun Slide.