南海及邻近地区面波层析成像和S波速度结构  

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

作　　者：黄忠贤[1] 胥颐[2] 

机构地区：[1]中国地震局地壳应力研究所,北京100085 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《地球物理学报》2011年第12期3089-3097,共9页Chinese Journal of Geophysics

基　　金：国家重点基础研究发展计划项目(2007CB411701);中国地质调查局科研项目(GZH200900504)资助

摘　　要：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,给出了各个单元的主要结构特征.(1)扬子地块具有厚而高速的岩石圈,华南褶皱带和印支地块具有活动陆块的结构特征,西菲律宾海盆表现为一个较老的稳定的海盆,而岛弧地带显示低速的岩石圈和俯冲板片引起的高速.(2)南海海盆岩石圈厚度60～70 km,横向变化不大,软流圈内低速不显著,整体上表现出一个已停止扩张的年轻海盆的结构特点.与东部中央海盆相比,西南次海盆的上地幔盖层速度和软流圈速度都较低.(3)在南海海盆周边的陆缘地区,岩石圈厚度变化较大,上地幔盖层和软流圈速度较低,明显低于海盆和外围的大陆地区.红河断裂带也表现类似现象,说明这些地区的岩石圈新生代以来经历了长期的构造作用.Abstract 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 ceasedspreading 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.

关 键 词：南海 岩石圈 速度结构 面波 层析成像 

分 类 号：P315[天文地球—地震学]