Rayleigh wave group velocity maps At short periods, group velocities are slow because of the thick, slow crust At long periods, group velocities are neutral to fast because the crust is compensated by fast material in the upper mantle At short periods, group velocities are slow because of the thick, slow crust At long periods, group velocities are neutral to fast because the crust is compensated by fast material in the upper mantle

Mantle structure: depth slices Low-velocity uppermost mantle beneath North-Central Tibet High-velocity material at 200 km beneath most of Tibet

Mantle structure: slice across Western Tibet Subduction of Indian lithosphere

Mantle structure: slice across Central Tibet Detached lithosphere

Mantle structure: slice across Eastern Tibet Subduction of Asian lithosphere ???

Main Belt Thrust Yarlung-Zangbo Suture Bangong-Nujiang Suture Jinsha River Suture Kunlun Fault Altyn Tagh Fault Interpretation of the tomographic model for Tibetan region Western Tibet 1.Subduction of the Indian lithosphere 2.Penetration of hot asthenospheric material from the North 3.Strong mid-crustal anisotropy is probably caused by the extended ductile deformation of the crust Western Tibet 1.Subduction of the Indian lithosphere 2.Penetration of hot asthenospheric material from the North 3.Strong mid-crustal anisotropy is probably caused by the extended ductile deformation of the crust depth (km) Central Tibet 1.Lithospheric detachment 2.Penetration of hot asthenospheric material from the North 3.Strong mid-crustal anisotropy is probably caused by the extended ductile deformation of the crust Central Tibet 1.Lithospheric detachment 2.Penetration of hot asthenospheric material from the North 3.Strong mid-crustal anisotropy is probably caused by the extended ductile deformation of the crust depth (km) Eastern Tibet 1.Possible subduction of the Asian lithosphere 2.Possible penetration of hot asthenospheric material from the South 3.Mid-crustal anisotropy is weaker than in Western and Central Tibet Eastern Tibet 1.Possible subduction of the Asian lithosphere 2.Possible penetration of hot asthenospheric material from the South 3.Mid-crustal anisotropy is weaker than in Western and Central Tibet depth (km)