Full-waveform Box Tomography for the Lithospheric Structure in South-central Tibetan Plateau

Tibetan Plateau is resulted from the collision between India and Eurasia ca 55 Ma. The fate of the subducted Indian crust has long been debated. The Hi-CLIMB seismic experiment (Nábělek et al., 2009) presented images indicating that the southern Tibetan Plateau was under-thrusted by the Indian plate up to ~31°N, and the Indian crust was partially decoupled from the mantle below. However, the structure and the dynamics of the underlying mantle remain enigmatic. Various geodynamic models have been proposed to explain the behavior of the mantle lithosphere across this collision zone. These include hypotheses involving lithospheric delamination, rollback, tearing, etc. Further information about the lithospheric mantle beneath Tibetan Plateau is required to better understand the history and current state of this continental collision. In this study, we conduct full-waveform inversion of P-wave and its coda using 14 teleseismic events recorded by the Hi-CLIMB stations, which mainly consist of an 800-km long sub-linear array of 189 broadband seismometers spaced at 5-15 km. Our analyses yield high-resolution 3-D models for the P- and S-wave speeds along with density in the south-central Tibetan Plateau, which covers key geological features including the Genge basin, the Himalayas, and the Lhasa and Qiangtang terranes. Our model resolves P- and S-wave velocity structures from the surface down to ~400 km depth and the density structure in the uppermost 100 km. Our new 3-D multi-parameter model is integrated with results from geochemical and geothermal simulations to evaluate the existing tectonic models, which sheds new light on the state of the Indian lithosphere beneath Tibetan Plateau.