Study Of Submarine Landslides And Trigger Mechanism Along The Continental Slope Of The Northern South China Sea

The northern South China Sea region subject to the periphery of the combinedeffects of three plates (Pacific Plate, the Eurasian Plate and the Indo-Australian Plate)has special structural position, so it is geology, energy, biotechnology and geopoliticalforefront of research in the field. Non-renewable and limited nature of oil and gasresources makes the marine oil and gas exploration gradually shift from offshore todeepwater continental shelf and slope areas. The northern South China Sea area is richin oil and gas resources and new clean energy-gas hydrates, so it become the primarytarget zone once again. In the course of exploration and trial mining, marine geologyand environmental studies of the continental slope the protection of safety ofengineering facilities. Therefore, the stability study of this area (mainly submarinelandslides and their trigger mechanism) has important theoretical and practicalsignificance.The main work in this paper is mainly around Qiongdongnan, Xisha, Shenhu,Dongsha four regions, where special2D survey lines lay. The research is focused onthe middle and the eastern of the northern South China Sea, that are Shenhu regionand Dongsha region. Based on high-resolution2D seismic line network in this area,this paper focused on interpreting the developmental characteristics of submarinelandslides. According to the geological-geomorphology development environment ofthe landslides, six types of landslides are divided. These are landslide slope beltlandslide, diapirs landslide, canyons landslide, volcanoes landslide, fault landslide,hydrate landslide. A submarine landslide slope area flat distribution is drawed. Thereare hydrate, volcanic and diapirs landslides in Dongsha slope. There are slope belt,hydrate, diapirs landslide in Shenhu slope. There are canyon and diapirs landslides inXisha slope. There are slope belt, volcanic landslide in Qiongdongnan slope.Landslide triggering mechanism is different under different developmentalenvironments. Landslides in Dongsha slope are mainly triggered by earthquakes andmagmatism. Landslides in Shenhu slope are mainly triggered by sea-level change, gashydrate decomposition, high deposition rate, unconsolidated sediments andmagmatism. Landslides in Xisha slope are mainly triggered by erosion andmagmatism. Landslides in Qiongdongnan slope are mainly triggered by earthquakes,faults and magmatism.This paper has a numerical calculation on the typical submarine landslides inDongsha slope and Shenhu slope. The results show that, the impact of hydratedecomposition on the seabed slope depends on the comparative strength of themechanical parameters of the decomposition of the hydrate layer with soil parameters.If the hydrate layer is greater intensity, submarine slope stability would not beaffected. If strength is small, the equivalent of weak layer will reduce the stability of the seabed slopes. When hydrate trigger submarine slope, the plastic zone was firstproduced from the hydrate layer. Once the hydrate layer produce an impact on thestability of submarine slope, sliding distance submarine slope will become great.