缅甸弧及邻区的壳幔S波速度结构与动力学过程

用适配滤波频时分析技术处理了锡龙（SHIO）、清迈（CHTO）、昆明（KMI）和拉萨LSA）台记录的长周期数字化面波记录，获取了穿过缅甸弧及周边地区的530条路径的Rayleigh波频散，这些频散的周期范围为10.45～105.03 s.在此基础上，以分格频散反演方法从混合路径频散中提取了1°×1°网格内的纯路径频散，并且由网格内的纯路径频散反演出深达200 km的S波速度结构，最后重建了缅甸弧及周边地区的S波速度三维结构.所得结果表明：大致以实皆断裂为分界，其东部地壳波速较低，其西部地壳波速较高.印度-缅甸地区岩石圈厚度为110～130 km，上地幔顶部S波速度为43～4.4 km/s；而缅甸弧东侧的滇缅泰地块下方为一低速地幔柱上涌区，其宽度为150～200 km左右，这里的岩石圈厚度为70～80 km，上地幔顶部S波速度为41～4.2 km/s.另外，S波速度结构还反映出这一构造格局呈南北向的空间展布，并且与该区地震震源分布、断裂走向、火山分布有很好的对应关系.

Crust-mantle velocity structure of S wave and dynamic process beneath Burma Arc and its adjacent regions

The Rayleigh dispersion data of 530 selected paths crossing Burma Arc and its adjacent regions are determined by applying the MF FTAN(Matched Filter Frequency-Time Analysis ) technique to long period data recorded at SHIO, CHTO, KMI, and LSA stations, the periods of the Rayleigh dispersion are in the range of 10.45～105.03 s. On this basis, a method of grid dispersion inversion is proposed to extract pure path dispersion in a 1°×1° grid from mixed path dispersion. Then, the S velocity structure to a depth of 200 km is inverted from pure-path dispersion in each grid cell, finally, the 3-D velocity structure of S wave is reconstructed beneath Burma Arc and its adjacent regions. The result shows that taking Sagain fault as the boundary, the velocity of crust on the west side of the fault is higher than one on the east side of the fault; lithosphere depth is in the range of 110～130 km and the S wave velocity at the top of upper mantle is 4.3～4.4 km/s beneath the Indo-Burma regions; however, on the east side of Burma Arc; there is a lower-velocity column of uprising mantle about 150～200 km wide beneath Yunnan-Myanmar-Thailand Block; the lithosphere depth is 70～80 km and the velocity of S wave at the top of mantle is 4.1～4.2 km/s in the area. On the other hand, the S wave velocity structure shows an EW(east-west) variation, this distribution feature corresponds to the distribution of epicenters and volcanoes, and the strike of faults.