三峡库区上地壳横波速度结构

S-Wave Velocity Structure of Upper Crust in Three Gorges Reservoir Region of the Yangtze River

为了更好地了解三峡库区的稳定性，利用三峡库区的流动宽频地震仪台阵于2011年4-5月期间观测的背景噪声数据，采用互相关方法提取了瑞利面波的格林函数，用多重滤波方法获得了瑞利面波的群速度频散曲线.利用走时层析成像方法获得了0.5-10.0s周期的纯路径频散曲线，进而反演获得了沿巴东-茅坪-土门方向的横波速度结构剖面，揭示了三峡地区上地壳的速度变化情况.研究表明：（1）研究区地下速度结构与地质构造关系密切，速度剖面上很好地反映了一个以黄陵背斜核部为中心的背斜构造；（2）九畹溪及其周边区域下方较快的速度变化可能与对应的区域断裂构造、地震活动性密切相关；（3）三斗坪地区上地壳表现为高速，表明三峡坝区处于构造稳定区域.

In order to make a better understanding of the stability of the Three Gorges Reservoir region,the profile of S-wave velocity structure along Badong-Maoping-Tumen is presented using the ambient noise data observed at 10 stations from mobile broadband seismic array which is located at Three Gorges Reservoir region.All of available vertical component time series dur-ing April and May,201 1 have been cross-correlated to estimate the empirical Green functions.Group velocity dispersion curves were measured by applying multiple filtering technique.Using these dispersion curves,we obtain high resolution pure-path dis-persions at 0.5-10 s periods.The S-wave velocity structure,which was reconstructed by inverting the pure-path dispersions, reveals the velocity variations of upper crust at Three Gorges Reservoir region.Main conclusions are as follows.（1）The velocity variations in the study region have a close relationship with the geological structure and the velocity profile suggests an anticline unit which core area is Huangling block.（2）The relative fast velocity variations beneath Jiuwanxi and its surrounding areas may correspond to the geological structure and earthquake activity there.（3）The high velocity of the upper crust in Sandouping in-dicates that the reservoir dam of Three Gorges is located at a tectonic stable region.