• 标题：Lithospheric mantle underneath the Tibetan Plateau does not escape southeastward
• 关键词：Eastern and southeastern Tibetan Plateau; Pn velocity; Uppermost mantle; Lithospheric mantle; Eastward escape
• 作者：

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A mass of lithospheric shortening occurred beneath the Tibetan Plateau due to the collision between the Indian and Eurasian plates. The extrusion of the upper crust beneath the Tibetan Plateau has been widely accepted, but whether the lithospheric mantle escapes laterally by creep deformation or rigid-block extrusion remains unclear. Based on the Pn travel time data, the velocity structure of the uppermost mantle in eastern and southeastern Tibetan Plateau was obtained by using the interstation travel-time difference method. The results show an obviously high Pn velocity beneath the Sichuan Basin and Qaidam Basin, indicating that the areas are stable blocks. The high Pn velocity beneath the eastern Lhasa terrane may be related to the underplating of the Indian lithospheric plate to the north. The Qilian block located in the north of the Kunlun fault appears as a normal Pn velocity, which indicates a mean lithospheric mantle thickness. A significantly low Pn velocity with an average of ~7.8 km/s in eastern and southeastern Tibetan Plateau, including the eastern Songpan–Ganzi terrane, the Chuan–Dian Diamond Block, and the northern part of Yunnan Province, indicates that the lithospheric mantle is relatively thin in these regions. Combined with other geologic and geophysical results, we propose that the lithospheric mantle of the plateau did not escape to eastern and southeastern Tibetan Plateau where the crust has been thickened by adding crustal material from the interior of the plateau