A Fully Three-Dimensional Tomography Study of Upper Mantle Structure Beneath Eastern Asia

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ZhaoEAR-0308403In this proposal, the PI plans to conduct a regional three-dimensional (3-D) tomography for the anisotropic shear-wave velocity in the mantle beneath Eastern Asia. This study will be carried out by taking advantage of a wide distribution of moderate-sized (magnitude 5-6) earthquakes in most parts of Eastern Asia, an increasing number of permanent seismic stations and the latest developments in the methodology for regional tomography. The data to be inverted will include the frequency-dependent travel-time and amplitude perturbations measured on intermediate-period (20-100s) three-component seismic records of surface waves, mantle-turning body waves and ScS reverberations. Moreover, these measurements obtained from regional, intermediate-period seismic waves will be inverted using accurate and realistic full 3-D Frechet kernels computed by a normal-mode coupling algorithm. The model parameters will include the 3-D radially-anisotropic shear-wave velocity and the topographies of the upper-mantle transition-zone discontinuities. In most parts of the region under study, the upper-mantle structure will be resolved on a horizontal scale of ~500 km and a vertical scale of ~100 km. Issues affecting tomography models, such as source-receiver coverage, inversion procedures, velocity-topography trade-off, anisotropy, and attenuation will be examined. This is the first application of full 3-D regional tomography approach to a continental region. It is also the first study in which the perturbations in velocity and discontinuity topography are jointly inverted. The results will provide constraints for the geodynamic evolution of Eastern Asia and its relation to surrounding tectonic regions. Broader impact: The PI works closely with graduate students on this and related regional tomography studies and methods and data and software will also be made available to the wider seismology community. The techniques developed here can be an ideal choice for other regional tomography studies, for example the mantle structure under the USArray.--