Solidification Texture of the Uppermost Inner Core

对地震波形进行分析，以确定地球固体核心小规模结构变化的空间频谱或结构。地震体波的形状和尾波在近垂直和近水平入射到内核边界上的敏感度有很大的不同，用来绘制内核非均匀结构的横向变化。固体内核结构的横向变化可以记录液体外核底部流体流动的横向变化，并限制内核的旋转与地幔的旋转锁定的程度。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，以及了解地球核心的小尺度结构如何与外核中的流体流动及其与磁场时间变化的关系。这项研究的结果对于理解液态外核的凝固如何维持地球磁场，以及地核的冷却如何与地幔的冷却和动力学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层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.