【摘要】 利用PASSCALI、NDEPTH-ⅡI、NDEPTH-Ⅲ、HIMNT等研究计划,及中国新疆地学断面和国家973项目在青藏高原布设的流动台站记录的到时数据,以及自1990年1月到2004年2月全球地震事件的震相报告,作者对覆盖印度大陆的恒河平原和整个青藏高原的305个地震台站记录的9649个远震事件,共139021条P波初至到时资料进行了层析成像反演.结果表明:印度岩石圈地幔在不同的位置向北俯冲的形态不同,但俯冲前缘都到达羌塘地体之下.沿88°E剖面显示,厚约100 km的印度岩石圈地幔从南部的恒河平原向北一直俯冲到青藏高原之下.在主边界逆冲断裂之下100 km深度处以约22°角度开始向北俯冲,俯冲最前缘到达羌塘地体的中部地区约34°N,之后进入上地幔深处.而沿北东方向的剖面则显示,印度岩石圈地幔以近水平的角度俯冲到青藏高原之下,向北越过班公-怒江缝合带,到达33°N附近,然后以大角度近乎垂直地向下俯冲断离,并引起地幔热物质的上涌,形成羌塘地体之下大规模的低速带.更多还原

【Abstract】 We have collected all the available arrival time data recorded by the temporary seismic stations from the projects of PASSCAL,INDEPTH-Ⅱ,INDEPTHⅢ, HIMNT,WKL and TIBET 973,and phase reports from the International Seismological Center from January 1990 to February 2004 in Tibet and its surrounding areas.In the tomographic inversion,we have used 139021 P-wave arrival times from 9649 teleseismic events recorded by 305 seismic stations.Our study area covers the southern Ganges plain in India to the northern Tarim basin and Qaidam basin in China.Our tomographic images show that the subducting angles of Indian lithospheric mantle are different under different areas,but their front locations are all beneath the Qiangtang terrane.The tomographic images along 88°E show that the Indian lithospheric mantle is underthrusting northward with a dip angle of about 22° beneath the center of Qiangtang terrane at about 34°N latitude,and its frontier has reached to the deep part of the upper mantle.The tomographic images along a northeasterly profile show that the Indian mantle has nearly horizontally underthrust under the Tibet from Ganges plain to 33°N.Then,the Indian mantle broke off down to the asthenosphere and caused the asthenophere upwelling.A consequence of the asthenophere upwelling was to form a big low-velocity zone beneath the Qiangtang terrane.更多还原