Mapping the Fine Structure of Earth's Inner Core with Seismic Array Data

这个项目将使用国际监测系统（IMS）地震台记录的高频地震波来绘制和模拟地球内核的精细结构。使IMS阵列台站用于探测和定位核武器试验的相同特性和技术，使它们成为观察与内核相互作用的通常微弱的地震相位的理想选择。虽然内核在物理上很小，但它对地球动力学起着很大的作用，更一般地说，对地球内部的热传递起着很大的作用。在同样的意义上，冰芯可以用来推断过去的气候波动，也有可能使用内核的径向结构的地震模型来限制地球磁场的历史。从IMS站收集的数据将通过波束形成、fk分析和相位加权叠加等标准阵列技术进行处理，以观察核心反射（ScP, PcP,PKiKP, SKiKP）和折射（PKPbc, PKPdf）。在同一地震记录上记录的相位之间的相对性质将用于减轻浅层结构的影响。具体研究目标包括利用PcP/PKiKP振幅比来约束内核顶部的剪切速度和跨越内核-外核边界（ICB）的密度跳变，模拟临界PKiKP相来约束ICB的厚度，利用准极性PKPbc和PKPdf相来评估ICB下各向异性不连续的假设，并通过分析透明区临界PKiKP相的余弦来评价内核散射假说

EAR-0229103Keith D. KoperThis project will use high frequency seismic waves recorded atseismograph stations of the International Monitoring System (IMS)to map and model the fine structure of Earth's inner core. The sameproperties and techniques that make IMS array stations useful fordetecting and locating nuclear weapons tests make them ideal forobserving the often faint seismic phases that interact withthe inner core. Although the inner core is quite small physicallyit plays a large role with respect to the geodynamo, and moregenerally with respect to heat transfer within the Earth. In thesame sense that ice cores can be used to deduce past climatefluctuations it may be possible to use seismic models of the fineradial structure of the inner core to constrain the history of Earth'smagnetic field.The data gathered from IMS stations will be processed withstandard array techniques such as beamforming, fk analysis, andphase-weighted stacking to observe core reflections (ScP, PcP,PKiKP, SKiKP) and refractions (PKPbc, PKPdf). Relative propertiesamong phases recorded on the same seismogram will be used tomitigate the effect of shallow structure. Specific researchtargets include using PcP/PKiKP amplitude ratios to constrainthe shear velocity at the top of the inner core and the densityjump across the inner core-outer core boundary (ICB), modelingprecritical PKiKP phases to constrain the thickness of the ICB,evaluating the hypothesis of an anisotropic discontinuity beneaththe ICB using quasi-polar PKPbc and PKPdf phases, and evaluatingthe inner-core scattering hypothesis by analyzing the codaof precritical PKiKP phases in the transparent zone.--