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Constraints on Inner Core Anisotropy Using Array Observations of P′P′
Author(s) -
Frost Daniel A.,
Romanowicz Barbara
Publication year - 2017
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 - 10.1002/2017gl075049
Subject(s) - anisotropy , inner core , core (optical fiber) , geology , polar , rotation (mathematics) , geodesy , sampling (signal processing) , geophysics , phase (matter) , latitude , physics , computational physics , geometry , optics , mathematics , astronomy , quantum mechanics , detector
Abstract Recent studies of PKPdf travel times suggest strong anisotropy (4% or more) in the quasi‐western inner core hemisphere. However, the availability of paths sampling at low angles to the Earth's rotation axis (the fast axis) is limited. To augment this sampling, we collected a travel time data set for the phase P′P′df (PKPPKPdf), for which at least one inner core leg is quasi‐polar, at two high latitude seismic arrays. We find that the inferred anisotropy is weak (on the order of 0.5 to 1.5%), confirming previous results based on a much smaller P′P′ data set. While previous models of inner core anisotropy required very strong alignment of anisotropic iron grains, our results are more easily explained by current dynamic models of inner core growth. We observe large travel time anomalies when one leg of P′P′df is along the South Sandwich to Alaska path, consistent with PKPdf observations, and warranting further investigation.