Investigation of Global Scale Seismic Mantle and Core Structure Using Forward and Inverse Approaches

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RomanowiczThis grant will support a program of investigation of lateral heterogeneity in the earth's mantle and core at the global scale, using seismological methods. There are two main components in this research program. The first is global seismic waveform tomography and related forward modeling. Global seismic tomography can provide constraints on key mantle dynamics questions such as: the fate of subducted slabs, the role of D" as a thermo-mechanical boundary layer, the depth of origin and role of mantle plumes in the global circulation, or the nature of coupling between upper and lower mantle and the distribution of geochemical reservoirs. The second component is the investigation of core-sensitive phases and their interpretation in terms of structure/anisotropy of the core and of the deep mantle. While a very small part of the earth, the inner core is thought to play an important role in the dynamics of the outer core and the magnetic field generation. Evidence for complexity in its anisotropic structure has been accumulating, and trade-offs between core and mantle structure need to be further explored.Under component (1), the investigators will extend their waveform tomography approach to include a combination of approximate analytical and exact numerical methods in the computation of synthetic waveforms and partial derivatives. Under component (2), they will continue to collect and analyze core sensitive travel time data to test recently proposed complex models of the inner core and further evaluate trade-offs between inner core, outer core and mantle structure.Broader Impacts: The proposed program of investigation of deep earth structure will benefit a broader community of non-seismologists in geophysics (geodynamicists, mineral physicists) and geochemists, in that it aims at providing seismological constraints on global geodynamical models of the earth's mantle (part 1 of this proposal) as well as the core (part 2 of this proposal).