【摘要】 利用中美合作Hi-Climb项目北段吉隆-鲁谷剖面的天然地震探测数据,拾取2004~2005年期间5级以上地震事件的P波与4级以上地震的Pn波震相的走时,通过多震相层析成像反演获得青藏高原腹地的地下500 km以上的P波速度扰动结构.结果表明雅江地区为北向倾斜的低速扰动,班公-怒江断裂下方存在向南俯冲并被印度板块俯冲挤压而回折的高速体,建立了印度板块在冈底斯地块下方拆沉并被雅江低速体穿越的构造样式.说明印度板块俯冲在到达班公-怒江缝合带之前已经开始消减,与拆沉位置对比发现,印度板块的前锋深部呈现多期多级次特征,并受到地幔热循环作用的影响.更多还原

【Abstract】 Utilizing the seismological data collected by Sino-US cooperated project Hi-Climb,crossing the north part of the profile from Gyirong to Lugu,we picked the arrival times of P phases from earthquakes larger than Mb 5.0 and Pn phases from that lager than Mb 4.0 recorded during 2004～2005.Through multi-phase tomography inversion the P wave velocity perturbations down to 500 km below the central part of Tibetan Plateau were determined.It is found that there is a northward dipping low velocity perturbation zone in the Yarlun-Tsangbo Suture area,and a southward subduction zone beneath Bangong-Nujiang Suture which may be lifted by Indian Plate subduction,and the delamination of Indian Plate beneath Gangdes block may be cut through by the low velocity zone at Yarlun Suture.The tectonic style illustrates that Indian Plate should have subducted before it may reach Bangong-Nujiang Suture,and that the frontier of Indian Plate presents multi-phase multi-level feature according to the delaminated position,and may also be affected by the thermo-cycle of lower mantle.更多还原