南海北部陆架主要地貌特征及灾害地质因素

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

利用最新高精度多波束水深资料,对南海北部陆架地貌类型和特征进行了系统的识别和分析,发现研究区活动沙波、滑塌体、隆起脊、沟槽和麻坑等灾害地质因素发育。沙波多为直线型沙波,小、中、大型沙波均有发育,自北向南随着水深增大,沙波规模增大,沙波的活动性显著增强。底流内波特征变化与沙波规模和迁移情况具有一致性,沙波的形成和迁移与内波活动密切相关。根据滑塌特征地貌识别出7处滑塌,新老滑塌均有发育,新滑塌多呈线状延伸,梯状滑塌特征明显,分析认为新滑塌近期并无进一步滑动的趋势。受古岸线残留地貌控制,南部地形起伏较大,发育一系列隆起脊,K1—K4隆起脊近NE—SW走向平行排列,K5隆起脊为E—W走向与之相交。另外,研究区发育大量麻坑,直径30～100m,麻坑深度1.0～3.0m。

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 mi- gration 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. Con- trolled by residual paleoeoastlines, the southern terrain of the region is characterized by a series of up- lift 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.