中国西部地壳上地幔速度和Q_β结构

VELOCITY AND Q_β IN THE WESTERN CONTINETAL CHINA

从穿越中国西部地区所有双台大圆路径中 ,选出Rayleigh波记录比较清晰且焦散效应相对较弱的 3条双台大圆路径。计算出双台间地震面波相速度频散 ,群速度频散和随周期变化的衰减因子 ,进而反演出 3条路径下地壳上地幔的平均S波速度和Qβ 结构。对应于兰州—高台路径 ,在约 72km深度的上地幔中开始出现低速和低Qβ 层 ,在深度为 6km～ 2 0km的地壳中 ,存在一低Qβ 层 ,而在其下 2 0km～ 34km深度的地壳中存在一高Qβ 夹层 ;对应于成都—乌鲁木齐路径 ,在约 86km深度的上地幔中开始出现低速Qβ 层 ,在 12 1km深度开始出现明显的低Qβ 层 ,在深度为 19km～ 34km的地壳中 ,存在一显著的高Qβ 层 ;对应于高台—拉萨路径 ,在约 84km深度的上地幔中开始出现低速和低Qβ 层 ,在 15km～2 9km深度的地壳中 ,存在一高Qβ 夹层。

By using a method which minimizes the effects of scattering and focusing, we select three two-station paths across the western continental China. eastern china thoroughly. Based on the dispersion of phase and group velocity and attenuation factor corresponding to each path, we acquire the wave velocity and Q β structure under the crust and upper mantle. Corresponding to the Lanzhou-Gaotai path, low-velocity and low-Q β layer appear in the upper mantle at about the depth of 72 km; in the crust, there is a low-Q β layer between 6 and 20 km deep, and a high-Q β layer between 20 and 34 km deep. Corresponding to the Chengdu-Wulumuqi path, there is an obvious high-Q β layer in crust between the depth of 19 and 34 km with both low-Q β adjacent layers; in the upper mantle obvious low-Q β and low-velocity layer appears at the depth of 121 km.Corresponding to the Gaotai-Lasa path, in the crust a high-Q β layer exists between the depth of 15 and 29 km, below it there is a low-Q β layer between the depth of 29 and 46 km, low-Q β layer and low-velocity begins to appear in the upper mantle at about 84 km deep.