Earthʼs inner core: Innermost inner core or hemispherical variations?

Lythgoe, K. H. and Deuss, A. and Rudge, J. F. and Neufeld, J. A. (2014) Earthʼs inner core: Innermost inner core or hemispherical variations? Earth and Planetary Science Letters, 385. pp. 181-189. ISSN 0012-821X DOI 10.1016/j.epsl.2013.10.049

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Abstract

The structure of Earthʼs deep inner core has important implications for core evolution, since it is thought to be related to the early stages of core formation. Previous studies have suggested that there exists an innermost inner core with distinct anisotropy relative to the rest of the inner core. Using an extensive new data set of handpicked absolute travel time observations of the inner core phase PKIKP, we find that the data are best explained by variations in anisotropy between two hemispheres and do not require an innermost inner core. We demonstrate that observations of an innermost inner core are an artifact from averaging over lateral anisotropy variations. More significantly we show that hemispherical variations in anisotropy, previously only imaged in the upper inner core, continue to its centre. The eastern region has 0.5–1.5% anisotropy, whereas the western region has 3.5–8.8% anisotropy increasing with depth, with a slow direction at 57–61° to the Earthʼs rotation axis at all depths. Such anisotropy is consistent with models of aligned hcp or bcc iron aggregates.

Item Type:	Article
Uncontrolled Keywords:	2013AREP; IA66;
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title:	Earth and Planetary Science Letters
Volume:	385
Page Range:	pp. 181-189
Identification Number:	10.1016/j.epsl.2013.10.049
Depositing User:	Sarah Humbert
Date Deposited:	24 Nov 2013 01:53
Last Modified:	16 Dec 2013 12:49
URI:	http://eprints.esc.cam.ac.uk/id/eprint/2920

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