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Inner core anisotropy

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Inner Core Anisotropy diagram

Located over 5000 km below the Earth’s surface, the inner core represents the most remote portion of our planet. Seismology has provided a wealth of information on the elastic behavior of this region.  It has been established that the inner core exhibits elastic anisotropy with compression waves traveling 3% faster in the polar than in the equatorial direction.  There may be additional complexities in the structure, such as variations in anisotropy with depth and differences between the eastern and western hemispheres.  Recently we demonstrated that by coupling a number of newly developed in-situ x-ray synchrotron techniques – hydrostatic axial x-ray diffraction, radial x-ray diffraction, nuclear resonant inelastic x-ray spectroscopy, and phonon inelastic x-ray spectroscopy – the elastic anisotropy of iron can be characterized at high pressure (Mao et al, GRL 2008).  We plan to extend these integrated studies to inner core conditions, which we hope will produce the accurate results critical for interpreting the observed inner core anisotropy and its implications for the structure, composition, and evolution of Earth’s core.