Publication Date:
2015-06-12
Description:
As we strive to understand the most remote region of our planet, one critical area of investigation is the uppermost inner core since its structure is related to solidification of outer core material at the inner core boundary (ICB). Previous seismic studies have used body waves to show that the top ~ 100km of the inner core is isotropic. However, radial anisotropy cannot be uniquely determined by body wave observations. Alternatively, normal mode centre frequencies are sensitive to spherically symmetric Earth structure, therefore may provide a constraint on the existence of radial anisotropy in the inner core. Here we show that normal mode centre frequency measurements are compatible with 2-5% radial anisotropy in the top ~100km of the inner core with a fast direction radially outwards and a slow direction along the ICB. Given the uncertainties in the mineral physics and processes that produce anisotropy, the observed radial anisotropy may be reconciled with predictions based on either solidification processes or from texturing due to anisotropic growth.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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