Heterogeneity and Anisotropy of Earth's Inner Core

Deuss, Arwen (2014) Heterogeneity and Anisotropy of Earth's Inner Core. Annual Review of Earth and Planetary Sciences, 42 (1). pp. 103-126. ISSN 0084-6597 DOI 10.1146/annurev-earth-060313-054658

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Abstract

Seismic observations provide strong evidence that Earth's inner core is anisotropic, with larger velocity in the polar than in the equatorial direction. The top 60–80 km of the inner core is isotropic; evidence for an innermost inner core is less compelling. The anisotropy is most likely due to alignment of hcp (hexagonal close-packed) iron crystals, aligned either during solidification or by deformation afterward. The existence of hemispherical variations used to be controversial, but there is now strong evidence from both seismic body wave and normal mode observations, showing stronger anisotropy, less attenuation, and a lower isotropic velocity in the western hemisphere. Two mechanisms have been proposed to explain the hemispherical pattern: either (a) inner core translation, wherein one hemisphere is melting and the other is solidifying, or (b) thermochemical convection in the outer core, leading to different solidification conditions at the inner core boundary. Neither is (yet) able to explain all seismically observed features, and a combination of different mechanisms is probably required.

Item Type:	Article
Uncontrolled Keywords:	2014AREP; IA68;
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title:	Annual Review of Earth and Planetary Sciences
Volume:	42
Page Range:	pp. 103-126
Identification Number:	10.1146/annurev-earth-060313-054658
Depositing User:	Sarah Humbert
Date Deposited:	25 Aug 2014 16:35
Last Modified:	07 Sep 2014 01:37
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3102

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