Fine Structure of the Mantle from Global Broadband Studies

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9902995VidaleThis project will sysematically analyze global broadband and selected regional data to addressquestions about the state of the Earth's mantle with new methods and greater resolution. The first project strives to understand the distribution of small-scale (~10 km) heterogeneity throughout the mantle using observation of scattered waves between P and PP. Envelop stacks of many P wave trains in the global seismic network database show diagnostic patterns of energy as a function of range and arrival time. Stacks of regional network observations will augment the analysis by providing higher-resolution observations for a few locales. Modeling with single and multiple scattering theories will provide a profile of scatterer strength as a function of depth in the entire mantle. The second task will be the analysis of the core-mantle boundary by reflected phases. We have identified more than 20,000 arrivals of PcP and ScP and will attempt to map the spatial variability of amplitude and frequency content of core reflections. In addition, we have obtained numerous West Coast regional array recordings of core reflections, which can provide high-resolution results for limited areas of the CMB.