Tomography of Gyirong- Lugu profile (Hi- Climb) and the subduction of Indian-Tibet collision

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.