南海及邻近地区面波层析成像和S波速度结构

本文介绍由面波层析成像得到的南海和邻近地区地壳上地幔三维S波速度结构.研究区域介于100°E～130°E和0°～30°N之间,南海位于区域中心,其北、西、南三面通过大陆架和陆坡分别与华南、印支和巽它地块相连,东面邻接台湾—菲律宾岛弧和西菲律宾海盆.由面波层析成像得到的速度结构横向变化与研究区内构造单元的划分基本相符,给...

S-wave velocity structure of South China Sea and surrounding regions from surface wave tomography

This paper presents the S wave velocity structure of South China Sea and surrounding regions derived from surface wave tomography. The study region lies between 100°E ~130°E and 0°~30°N, and is separated by continental shelves and slopes from South China, Indochina, and Sunda blocks on the north, west, and south side, respectively. On its east there are island arcs and the west Philippine Sea. The lateral variation of the velocity structure consists basically with the tectonic division of this region, and shows the major structural features of each tectonic unit. (1) The Yangtze block has a thick lithosphere of high velocity, South China fold belt and Indochina block show the features of active land mass, and the west Philippine Sea appears as a relatively old and stable sea basin, while the island arcs exhibit low-velocity lithosphere and subducted high-velocity slabs. (2) The lithosphere thickness of South China Sea basin is 60~70 km and varies insignificantly laterally. The velocity in the asthenosphere is not remarkably low. On the whole, the velocity structure tallies with a young sea basin which had ceased spreading in mid-Miocene. Compared to the East (Central) Sea Basin, the velocities in the lid and asthenosphere of the Southwest Sea Basin are relatively low. (3) In the continental margin areas surrounding South China Sea basin, lithosphere thickness varies remarkably, the velocity of lid and asthenosphere is significantly lower than that in the sea basin and surrounding land areas. Similar phenomena are also seen in the Honghe Fault zone, indicating that the lithosphere in these areas has undergone long-lasting tectonic events in the Cenozoic.