华北地区三维地壳上地幔结构

本文用均等显示滤波频时分析方法分析了长周期瑞利面波资料,获得了路经中国大陆及邻区的238条混合路径的面波群速度频散,其周期范围为10.5-113s.用改进的分格反演方法从混合路径频散中提取出位于华北地区的12个4°×4°网格单元的纯路径频散并反演其地壳上地幔结构.所得结果表明,华北地区地壳上地幔结构横向变化显著;从东向西地壳逐渐变厚;位于华北东部的分格在地壳中20km深处普遍存在低速层,整个华北地区上地幔低速层埋藏较浅,一般为55-100km之间.各个网格上地幔低速层的速度不尽相同.

THREE-DIMENSIONAL CRUST AND UPPER MANTLE STRUCTURE OF THE NORTH CHINA REGION

The data of long period Rayleigh surface wave have been processed in the present study by the "Display-Equalized Filter Frequency-Time Analysis" technique. The dispersion of the group velocity of surface waves have been obtained from 238 mixed-pathes travelling through China's continent and its surrounded area with the periods range from 10.5s till 113s. Accordingly, the pure-path dispersions for 12 cells of 4°×4° in North China have been extracted by using the modified "grid-dispersion inversion" method from the mixed-path dispersion measurements, and an inversion has thus been made of the crust and upper mantle. The results obtained show a noticeable leteral change in- the structure of crust and upper-mantle in North China. The crust has been thickened gradually from the east to the west. In the cells on the eastern North China there are low velocity layers existing generally at the depth of 20 km in the crust. The low velocity layers in the upper-mantle of the whole North China area are relatively shallowly buried: generally at the depths from 55 km to 100 km. The velocity of a low velocity layer somewhat differs for different cells.