Solidification Texture of the Uppermost Inner Core

对地震波形进行分析，以确定地球固体内核小尺度结构变化的空间谱或结构。利用地震体波的形状和尾波在接近垂直角度和接近水平角度入射于内核边界的强烈不同的敏感性来绘制内核非均质结构的横向变化。固体内核结构的横向变化可能记录了液体外核底部流体流动的横向变化，并限制了内核旋转锁定于地幔旋转的程度。两名研究生参与了这项研究。具有更广泛影响的研究成果包括控制地球小尺度非均质性对地震波形影响的定性和定量规则，以及了解地球内核的小尺度结构与外核流体流动的关系及其与磁场时间变化的关系。这项研究的结果对于理解固体内核如何从液体外核中凝固来维持地球磁场以及地核的冷却如何与地幔的冷却和动态演化相耦合具有重要意义。地球的磁场和冷却历史对地球大气和地表生命的演化都很重要。

Seismic waveforms are analyzed to determine the spatial spectrum or texture of small scale structural variations in Earth's solid inner core. Strongly differing sensitivities of the shapes and codas of earthquake body waves incident at near vertical versus near horizontal angles on the inner core boundary are exploited to map lateral variations in the heterogeneous texture of the inner core. Lateral variations in the texture of the solid inner core may record lateral variations in fluid flow at the bottom of the liquid outer core and constrain the extent to which the rotation of the inner core is locked to rotation of the mantle. Two graduate students participate in this study. Research products having a broader impact include qualitative and quantitative rules governing effects of small scale heterogeneity in the earth on seismic waveforms, and an understanding of how small scale structure in the earth's inner core is related to fluid flow in the outer core and its relation to time variations in the magnetic field. Results of this study are important to understanding how the solidification of the solid inner core from the liquid outer core sustains Earth's magnetic field and how the cooling of the Earth's core is coupled to the cooling and dynamic evolution of Earth's mantle. Both the magnetic field and cooling history of Earth are important to the evolution of Earth's atmosphere and surface life.