【摘要】 用分布于欧亚大陆及西太平洋地区106个宽频带数字地震台站约2万多个长周期波形记录,挑选出沿10600条大圆路径传播的瑞利面波,采用频散分析及波形拟合反演方法,对中国及相邻地区地壳上地幔进行高分辨率三维层析成像。瑞利面波高分辨率速度成像表明,从上地壳到70km深,在东亚东部及西太平洋边缘海地区均为高速分布,西部以青藏高原为中心呈极低速分布。从100～250km深,在东亚东部及西太平洋边缘海,自北向南显示出一条宽2500～4000km,长约8000km的巨型低速异常带。在深度300～400km的平面图上,速度差异幅度不大,塔里木—扬子地块仍然显示为高速分布。东西两部分岩石圈与软流圈的结构有着巨大的差异。西部主要是印度板块与欧亚板块碰撞引起的岩石圈汇聚增厚区,东部则主要是由于软流圈上涌(地幔热物质上升)引起的岩石圈拉张减薄区。古新世印度与欧亚大陆的碰撞汇聚,岩石圈板片以低角度下插到青藏高原之下,引起高原隆起和地壳增厚,西部地区成为岩石圈汇聚区。中生代中晚期东亚大陆东缘岩石圈解体,软流圈物质上涌,岩石圈减薄张裂,形成巨型低速带,并演化为东亚裂谷系。现今的西太平洋边缘海、沟弧盆体系是新生代中晚期太平洋板块、澳大利亚板块与欧亚板块相互作用形成的。更多还原

【Abstract】 Rayleigh surface waves propagating along 10,600 great-circle paths were selected using more than 20,000 long-period waveform records from 106 wide-band digital seismic stations distributed in Eurasia and the Western Pacific, and high-resolution 3D tomographic imaging of the crust and upper mantle in China and its adjacent regions was performed using the inversion of both dispersion analysis and waveform fitting. The high-resolution Rayleigh surface wave tomographic imaging indicates that: from the upper crust to 70 km depth, high velocities are displayed in the eastern part of East Asia and Western Pacific marginal seas, while very low velocities distributed in the western region centering around the Qinghai-Tibet Plateau; from the 100 to 250 km depth, a giant low-velocity anomaly belt ~250 to 400 km wide and ~8000 km long are shown in the eastern part of East Asia and Western Pacific marginal seas; from the 300 to 400 km depth, there is no appreciable velocity difference and high velocities are still displayed from the Tarim block to Yangtze block. There exist significant differences in lithospheric and asthenospheric structure between the eastern and western parts with longitude 110°E as the boundary. The western part is the lithospheric thickening convergent region formed by India-Eurasia collision, whereas the eastern part the lithospheric extension-thinning region arising from upwelling of asthenospheric material (rise of mantle thermal material). Due to the Paleocene India-Eurasia collision and convergence, the Indian lithospheric sheet was subducted beneath the Qinghai-Tibet Plateau at low angles, causing the plateau uplift and crustal thickening; thus the western part became a lithospheric region. In the Mid-Late Mesozoic, the lithosphere beneath the eastern margin of the East Asian continent was disassembled; as a result, the asthenospheric material upwelled and the lithosphere underwent extension and thinning, thus forming a giant low-velocity zone, which later evolved into the East Asian rift system. The present marginal seas and trench-arc-basin system of the Western Pacific was formed by interaction of the Pacific plate, Australian plate and Eurasia plate in the Mid-Late Cenozoic.更多还原