Illuminating the heterogeneous Earth based on numerical simulations of seismic waves: from global tomography to subduction-zone imaging

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Understanding the internal processes and dynamic evolution of our planet Earth has been one of the fundamental scientific questions for earth scientists. The tectonic events in the past are responsible for shaping the topographic and geological features observed on the surface, while the internal geodynamic circulation is the main engine driving complex plate motions. These plate motions and associated tectonic stress are often manifested as earthquakes, many of which cause severe damage over large areas. On the other hand, seismic waves emitted from these earthquakes provide an essential tool for illuminating heterogeneous structures of the Earth's interior and present direct evidence for the underlying tectonic processes. This proposal aims to continue our involvement in the development of forward seismic wave simulation techniques, and further advance innovative seismic imaging tools based on these numerical simulations to map internal structures of the Earth at both global and continental scales. For the whole globe, we will utilize a finite-frequency sensitivity kernel database computed fully numerically to generated updated shear and bulk-sound velocity models for the whole mantle. The large number of diffracted wave measurements will boost the resolution of the models above the core-mantle-boundary (CMB) and help provide better constraints on the Large Low Shear Velocity Provinces (LLSVPs) and ancient subducted slabs accumulating at the CMB. At regional scales, we will apply 2D and 3D SEM-FK hybrid techniques to both forward modelling and inversion of subduction zones beneath southern and central Alaska, with the goal of improving the locations and velocity variations of subducted oceanic crust and lithospheric mantle, the Moho interface and the overriding plate, and contributing to the interdisciplinary discussions on subduction zone processes.**