Tracing the Indian lithospheric mantle beneath central Tibetan Plateau using teleseismic tomography

We determined a detailed three-dimensional P-wave velocity structure of the crust and upper mantle down to 400 km depth beneath central Tibet by applying teleseismic tomography to 28,146 high-quality P-wave arrival times. The data were collected very carefully from the original seismograms of 1625 teleseismic events recorded by 131 broadband stations of five portable seismic networks deployed in central Tibet. Our results show that the Indian lithospheric mantle has subducted beneath central Tibet and its frontier has passed through the Bangong-Nujiang Suture and extended northward beneath the Qiangtang Terrane at 34 degrees north latitude. A prominent low-velocity anomaly is revealed within the Tethyan Himalayan Sequences close to the Yarlung-Zangbo Suture which is the boundary between the Tethyan Himalayan Sequences and the Lhasa Terrane. The subduction of the Indian lithospheric mantle has caused the east-west extension in central Tibet. The Indian slab beneath the region has not sutured with the Asian lithospheric mantle in the north. The obtained tomographic images can explain many geological and geophysical features such as strong seismic anisotropy in the upper mantle and K-rich and ultra-potassic lavas in northern Tibet. (C) 2010 Elsevier B.V. All rights reserved.