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Seismic anisotropy in the top 400 km of the inner core beneath the “eastern” hemisphere
Author(s) -
Niu Fenglin,
Wen Lianxing
Publication year - 2002
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 - 10.1029/2001gl014118
Subject(s) - geology , inner core , polar , southern hemisphere , anisotropy , core (optical fiber) , geodesy , apparent polar wander , geophysics , northern hemisphere , seismology , atmospheric sciences , physics , paleomagnetism , climatology , optics , astronomy
Depth variation in seismic anisotropy at the top 400 km of the inner core beneath the “eastern” hemisphere is investigated by comparing the differential travel times of PKP phases recorded at distances from 127° to 160°. At distances less than about 150°, there is no noticeable difference in differential travel times for PKP phases sampling both the polar and the equatorial paths. At greater distances, however, PKIKP phases arrive systematically earlier (about 0 ∼ 0.5 second) in the polar path than in the equatorial path. These observations suggest that, in the “eastern” hemisphere, seismic anisotropy exists only in depths greater than about 200 km below the inner core boundary (ICB) with seismic velocities along the polar paths (an average of 27.6° from the earth's spin axis) being 0.4% faster than those along the equatorial paths.