Seismological Structure of the Inner Core and Core-Mantle Boundary

EAR0003557（PH#7x）提案摘要标题：内核和核幔边界的地震学结构PI：Kenneth C. Creager，华盛顿大学我们建议将发展良好的新方法应用于全球数字数据，以检查内核和最低地幔的各向异性和各向同性结构。 我们计划分析五个不同的压缩波（PKPAB，PKPBC，PKPCD，PKPDF和散射相位），通过地球的核心传播的波形和差分旅行时间，以检查大规模的弹性各向异性的变化内的内核和散射在地幔的基础。 我们还将研究内核顶部和外核底部的边界层。 此外，我们将应用一种新的，最近开发的方法来探索在地幔底部的方位各向异性。 到目前为止的结果表明，澳大利亚东南部下方有很强的各向异性，这可能与塔斯马尼亚附近的热点有关。 大规模的横向变化的内核似乎完全与各向异性，而地幔表现出各向同性和各向异性的变化相结合。 由于内层的粘度比地幔小许多数量级，它不能支持密度的显著大尺度横向变化。 由于改变密度（温度和化学）的机制与改变各向同性波速的机制相同，因此内核内的各向同性不均匀性确实应该很小。 另外两个新提出的项目使用ScP和PKP前体作为探针探索最低地幔的精细结构。

Abstract for proposal EAR0003557 (PH #7x)Title: Seismological Structure of the Inner Core and Core-Mantle BoundaryPI: Kenneth C. Creager, University of WashingtonWe propose to apply well developed and new methods to global digital data to examine the anisotropic and isotropic structure of the inner core and lowermost mantle. We plan to analyze waveforms and differential travel times of five distinct compressional waves (PKPAB, PKPBC, PKPCD, PKPDF, and scattered phases) that propagate through the Earth's core to examine the large-scale variability of elastic anisotropy within the inner core and scattering at the base of the mantle. We will also investigate the boundary layers at the top of the inner core and the bottom of the outer core. In addition, we will apply a new, recently developed method to explore azimuthal anisotropy at the base of the mantle. Results to date suggest strong anisotropy beneath southeastern Australia, perhaps associated with the hotspot near Tasmania. Large-scale lateral variations in the inner core seem to be entirely associated with anisotropy, while the mantle exhibits a combination of isotropic and anisotropic variability. Because the viscosity of the inner is many orders of magnitude less than the mantle, it cannot support significant large-scale lateral variations in density. Because the mechanisms that change density (temperature and chemistry) are the same as those that change isotropic wave speeds, isotropic heterogeneity within the inner core should indeed be small. Two other new proposed projects explore the fine structure of the lowermost mantle using ScP and PKP precursors as probes.