中文摘要：

利用云南数字地震台网的区域地震波形资料，对川滇地区的地壳上地幔速度结构进行了初步研究．结果表明，川滇地区上地幔顶部P波速度较小，约7．8km／s，P波速度在上地幔表现为较小的正速度梯度，S波在100～160km深度范围内表现为弱低速层．对于较短的观测路径，不同路径的平均P波和S波速度存在明显的横向变化．与川滇菱形块体内部的速度结构不同，在块体边界附近可以观测到比较明显的上地壳低速层，我们认为它可能与块体边界的断裂带有关；川滇菱形块体内部存在的下地壳低速层，有利于块体向南滑动，而中上地壳没有明显低速结构，可能表明川滇菱形块体向南滑动的解耦深度至少在下地壳．根据不同路径的反演结果，给出了云南中部地区地壳内部的平均速度结构．

英文摘要：

The crustal and upper mantle velocity structure beneath Chuandian region has been studied by using the regional waveform data from digital seismic network of Yunnan province. The inversion result shows that the P-wave velocity in upper most mantle is relatively low, about 7.8 km/s in Chuandian region, with a small positive velocity gradient in upper mantle. The weak low S-wave velocity zone is between 100 km and 160 kin. For shorter paths, the average P and S-wave velocity structures vary obviously with paths. Different from the structures within the Chuandian rhombic block, a low velocity zone in upper crust can be observed near the boundary of the block. We inferred the low velocity zone might be related to fault zone near the boundary. The existence of low velocity zone in lower crust within Chuandian rhombic block will make the block easier to slip. Because there is no obvious low velocity zone in upper and middle crust, we consider the uncoupled depth of north toward slipping of Chuandian rhombic block might be occurred at lower crust or even deeper. Based on the inversion results of different paths, the average crustal velocity model in central area of Yunnan province is also given in this paper.