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.
