GEOMORPHOLOGY AND HAZARDOUS GEOLOGICAL FACTORS ON THE CONTINENTAL SHELF OF THE NORTHERN SOUTH CHINA SEA

The characteristics of geomorphology of the continental shelf of the northern South China Sea were studied and analyzed with the latest multi-beam bathymetric data, upon which a classification system was proposed in this paper. Results show that active sand waves, slides, uplift ridges, trenches and pockmarks are widely distributed in the study area. Three kinds of sand waves have been found and most of them are linear. The scale of sand waves increases with the water depth deepening toward the south and the enhancement of activity of sand waves. The alteration of the scale and migration of sand waves are consistent with the internal-wave activity. 7 slides were identified in the study area including old and modern ones. Most of the modern slides stretch linearly, and some slides are step-shaped with obvious slumping characteristics. Modern slides are not active nowadays. Controlled by residual paleocoastlines, the southern terrain of the region is characterized by a series of uplift ridges. Uplift ridges K1-K4 are parallel in NE-SW direction, while the uplift ridge K5 intersecting with the former ridges is in E-W direction. In addition, many pockmarks occur in the study area. The diameter of these pockmarks varies in a range of 30 to 100 m, with a depth from 1.0 to 3.0 m.