青藏高原地震波三维速度结构的研究

Research on the 3-D Seismic Velocity Structures in Qinghai-Xizang Plateau

根据青藏高原及其邻区的模拟地震台站和宽频带数字地震记录资料 ,采用区域体波层析成像和瑞利面波层析成像 ,反演得到了青藏高原地区的三维地震波速度结构。两种层析成像方法得到的地壳上地幔P波和S波速度结构的结果非常相似 ,它们显示 ,青藏高原南部的拉萨块体的上地壳存在明显的低速区 ,青藏高原北部的羌塘地区的下地壳和上地幔顶部相对速度较低。这些结果与青藏高原南、北部处于碰撞过程中的不同阶段有关。

Based on the recording data from the synthetic and broadband digital seismic stations in and around Qinghai-Xizang Plateau,the 3-D seismic velocity structures in Qinghai-Xizang Plateau were obtained by using the regional body wave tomography and surface wave tomography. The results from these two tomography methods have similar characteristics for P- and S- wave velocity structure in crust and uppermost mantle. They show that there are remarkable low velocity zones in the upper crust of Lhasa block in the southern Xizang and the lower crust and uppermost mantle of Qiangtang block in the northern Xizang. These phenomena may be related to the different steps of collision process for southern and northern Xizang.