Joint tomography with local body wave traveltime data and ambient noise surface wave dispersion: Application in the eastern margin of Tibetan plateau

Abstract:

Accurate and reliable velocity structure of the crust and upper mantle may provide key constraints on the tectonics and deep geodynamics. Seismic tomography methods with single dataset, such as body wave travel time and surface wave dispersions, have already obtained abundant results in the 3-D velocity structures of the crust and upper mantle. However, joint tomography methods are helpful to minimize the geophysical inversion non-uniqueness and improve the reliability and accuracy of the inversions compared to single tomography method. Recently, we developed the joint tomographic method of local body wave travel time and ambient noise surface wave dispersion, to take advantage of shallow sensitivity of surface wave data and deeper sensitivity of body wave data. In order to integrate the linear inversion equations from local earthquake body wave travel time tomography and noise surface wave tomography, the direct surface wave tomography method for 3-D velocity structures from dispersion data is developed. Unified form of the tomographic equation systems for both body and surface wave inversions makes the joint method efficient and effective, which can also accelerate the convergence of the tomographic inversion with limited iterations. With the joint tomographic method, we conduct tomographic inversion in the eastern margin of the Tibetan plateau. The obtained velocity structures of the crust and uppermost mantle from the joint inversion are better constraint and well improved compared to that from individual body or surface wave tomography, which could provide better 3-D model for the studies of deep tectonics and geodynamics in the Tibetan plateau.