High-resolution Mapping of Seismic Structures in the Lower Mantle

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The Principal Investigator continues the work on mapping the "African anomaly" and the "Pacific anomaly", and expands the study to other regions of the core-mantle boundary (CMB). The continued studies of the two anomalies include: mapping the geographic extent of the "African anomaly" in the lower mantle section by section, constraining the anisotropic behaviors of the base of the "African anomaly", mapping the geographic extent of the base of the "Pacific anomaly", constraining the structural and velocity features of the "Pacific anomaly" in the lower mantle and its structural connection to the base, and mapping the lateral variations of structural feature, length-scale and velocity reductions of the base of the "Pacific anomaly" and the anomaly in the lower mantle. The expanded study focuses on the seismic structures near the CMB beneath Philippines, South China Sea and central China. The Principal Investigator also explores possible interpretations and implications of the seismic results, in the context of mantle composition, temperature, dynamics and the relationship to the observations in other disciplines. The intellectual merits of the proposal include collection, identification, interpretation and waveform and travel time modeling of high-quality anomalous seismic data, with a scientific goal of mapping detailed structural features and velocity structures in several regions of the CMB, and structural features and velocity structures of the two prominent low-velocity anomalies in the lower mantle. Besides the training of a graduate student, the proposal has broad impacts on our further understanding of the thermal evolution of the Earth, thermal-chemical convection in the mantle, thermal-chemical mantle plume, dynamics and composition of the two prominent anomalies, the origin and distribution of geochemical reservoirs in the mantle, and relationship of mantle seismic heterogeneities to the geochemical signatures observed at the surface of the Earth including "the DUPAL anomaly".