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Seismic anisotropy of the inner core
Author(s) -
Sayers Colin M.
Publication year - 1989
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 - 10.1029/gl016i003p00267
Subject(s) - anisotropy , inner core , crystallite , seismic anisotropy , rotation (mathematics) , core (optical fiber) , spherical harmonics , symmetry (geometry) , orientation (vector space) , geometry , distribution function , physics , condensed matter physics , geology , materials science , crystallography , geophysics , mathematics , optics , chemistry , thermodynamics , quantum mechanics
Recent studies of seismic travel times and free oscillations have been interpreted in terms of an anisotropic inner core with cylindrical symmetry aligned with the earth's axis of rotation. The inner core is believed to consist of hexagonal close‐packed (hcp) iron. In this letter the velocity anisotropy is used to determine the coefficients W lmn of a series expansion of the crystallite orientation distribution function in generalised spherical harmonics. This function gives the probability of a crystallite having a given orientation with respect to a set of axes fixed in the core. The solution to this problem enables construction of crystallographic pole figures, which suggest a strong alignment of hcp Fe c‐axes along the earth's axis of rotation.