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利用中国台湾地震台网1992~2004年间记录到的P波和S波到时数据,使用地震层析成像方法联合反演了台湾及邻近地区地壳上地幔的P波速度和Vp/Vs波速比结构.与已有结果相比,采用的球坐标系有限差分算法适合于地壳波速结构强烈不均匀的情况,能够提高走时计算和三维射线追踪的准确程度,而联合反演得到的P波速度、Vp/Vs波速比及其重新定位后的地震分布为揭示壳幔结构的横向变化和深部特征提供了更多约束.结果表明:在地壳浅表层,沉积盆地和造山带具有明显不同的波速特征,沉积盆地P波速度偏低、Vp/Vs波速比偏高,造山带P波速度偏高、Vp/Vs波速比偏低;台东纵谷作为欧亚大陆和菲律宾海板块的碰撞缝合带,Vp/Vs波速比明显偏高,并延伸至中、下地壳和上地幔,反映了岩石破裂、部分熔融和流体活动对壳幔深部物质的影响;台湾东北部琉球岛弧附近的P波速度、Vp/Vs波速比和重新定位后的地震分布勾画出了菲律宾海板块俯冲至欧亚大陆下方的形态,高速的海洋俯冲板片及板片上方P波低速和高Vp/Vs波速比的特征一直延伸至80km;沿着东西向的纵向波速剖面,地壳厚度在中央山脉东侧达到60km左右,并呈现向东倾的趋势,反映出欧亚大陆板块的向东俯冲和挤压使造山带中下地壳物质变形增厚.
Using P-wave and S-wave arrival data recorded by the Taiwan Earthquake Network of China from 1992 to 2004, the P-wave velocities and Vp / Vs velocities of the crust and upper mantle in Taiwan and its adjacent regions were jointly retrieved using seismic tomography Compared with the existing results, the finite difference method of spherical coordinate system is suitable for the case that the crustal wave velocity structure is strongly inhomogeneous, which can improve the accuracy of traveltime calculation and 3D ray tracing, and the P-wave velocity, Vp / Vs and their post-relocation seismic distribution provide more constraints to reveal the lateral variation and deep features of the crust and mantle structure.The results show that there are obviously different characteristics of velocity and sediment in the shallow crust, sedimentary basin and orogenic belt The P wave velocity is low in the basin, the Vp / Vs wave velocity ratio is high, the P wave velocity in the orogenic belt is high, and the Vp / Vs wave velocity ratio is low. The Taipung Rift as the collision suture in Eurasia and Philippine Sea Plate, The Vs velocity ratio is obviously higher and extends to the middle and lower crust and the upper mantle, reflecting the influence of rock rupture, partial melting and fluid activities on deep crust and mantle material. The P wave velocity, Vp / Vs wave The velocity ratio and the post-relocation seismicity profile delineate the subduction of the Philippine Sea plate to the lower part of the Eurasian continent, characterized by the characteristics of P-wave velocity and Vp / Vs velocities above the high-speed oceanic submerged plates and plates extending up to 80 km Along the east-west longitudinal wave velocity profile, the thickness of the crust reaches about 60 km on the eastern side of the Central Mountain Range and tends to eastward, indicating that the east subduction and extrusion of the Eurasian plate deform the middle and lower crustal materials of the orogenic belt Thickening