Crustal and Uppermost Mantle Anisotropy Beneath Tibet: New Constraints on Deformation

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The PIs will apply innovations in seismic surface wave tomography to burgeoningbroadband seismic data sets in China to construct a 3-D model of radial and azimuthal anisotropy within the crust and uppermost mantle beneath and surrounding much of Tibet. The new tomographic methods include ambient noise tomography and array-based earthquake tomography that promise new structural constraints on isotopic and anisotropic structures from the shallow crust to mantle depths of at least 150 km with a lateral resolution of about 100 kmacross most of the study region. Targeted data sets leverage past and on-going US PASSCAL experiments by introducing a vast new data resource, the Chinese provincial networks surrounding Tibet. This work will be facilitated by collaboration with researchers at the Institute of Geodesy and Geophysics of the Chinese National Academy of Sciences in Wuhan, China.Preliminary proof-of-concept data processing and inversion efforts establish the quality of the constituent data sets and guarantee the production of integrated isotropic and anisotropic models of the crust and uppermost mantle across all of Tibet.This work is motivated to gain new insight into fundamental questions related to the continental collision between India and Asia; in particular, the role of the Indian and Asian mantle lithospheres in the collision and how the crust deforms in response to the collision. Detailed consideration of these questions requires high resolution 3D models of isotropic and anisotropic seismic variables in the crust and uppermost mantle across all of Tibet. Anisotropic models especially will provide new constraints on the vertical coherence of strains in the crust that will help resolve debate between competing theories of crustal deformation in response to continental collision.