CRUSTAL STRUCTURE IN CHINA FROM SURFACE WAVES

In this paper, numerical inversion from surface waves dispersion gives the layered structures for some regions in China.The results of this work show that the crust in China can be divided into five continental major blocks: Tibetan Plateau, Mongolian Plateau, North China, South China and Tarim Basin. In general, there are three layers (sediments, granitic and basaltic layers) in the crust. The seismic wave velocities in the upper mantle and basaltic layer for the latter four regions are almost the same. The average velocities in Tibet and in North China are lower than the other regions and the lateral heterogeneity is quite obvious. The Conrad interface is not a steady and sharp discontinuity. In some parts low velocity layers do exist, the high seismicity in these two regions is directly related to the deep crustal structure. The crusts of the other three regions show some characteristics of stable platform. The coastal crust can be divided into two regions by the mouth of Yangtze River, belonging to the crusts of North and South China respectively.The crustal thicknesses in China are 32-40 km. for East China, 60-70 km. for Tibet. The thickest sedimentary layer is found in the Tarim Basin amounting to about 11 km., but for other regions it is generally 3-8 km.