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Sharp hemisphere boundaries in a translating inner core
Author(s) -
Geballe Z. M.,
Lasbleis M.,
Cormier V. F.,
Day E. A.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50372
Subject(s) - inner core , geology , core (optical fiber) , isotropy , boundary (topology) , anisotropy , geophysics , outer core , core–mantle boundary , translation (biology) , geometry , transition zone , physics , mathematics , optics , mathematical analysis , chemistry , biochemistry , messenger rna , gene
Geodynamic models of a convectively translating inner core have recently been proposed that would account for the seismically observed differences in isotropic velocity between the eastern and western hemispheres of the inner core. These models, however, have previously been thought to be incompatible with seismic observations of a 1.5% P wave velocity change occurring over an 800 km wide region at the boundary between hemispheres of the inner core. Here we show that if rigid translation occurs, the age of material in the 100 km below the inner core boundary changes quickly as it crosses the boundary between the western and eastern hemispheres. We then forward model seismic traveltimes to show that the sharp transition in V P between hemispheres may be explained by a random distribution of highly oriented crystalline domains that grow during translation and are composed of material with relatively high elastic anisotropy (up to 12%).