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

Keith D.该项目将利用国际监测系统地震仪台站记录的高频地震波来绘制地球内核的精细结构图和模型。IMS阵列站用于探测和定位核武器试验的相同属性和技术使其成为观测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，但它在地球发电机方面起着重要作用，更广泛地说，它在地球内部的热传递方面起着重要作用。在同样的意义上，冰芯可以用来推断过去的气候波动，也可以使用内核精细径向结构的地震模型来约束地球磁场的历史。从国际监测系统台站收集的数据将用标准阵列技术处理，如波束形成、fk分析和相位加权叠加，以观察核反射（ScP、PcP、PKiKP、SKiKP）和屈光度（PKPbc、PKPdf）。利用同一地震记录上记录的各震相之间的相对性质来抵消浅层构造的影响。具体的研究目标包括：利用PcP/PKiKP振幅比来约束内核顶部的剪切速度和穿过内核-外核边界（ICB）的密度跃变，模拟预临界PKiKP相来约束ICB的厚度，利用准极性PKPbc和PKPdf相来评估ICB下的各向异性不连续性假设，并通过分析透明区中前临界PKiKP相的尾波来评估内核散射假设。

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.--