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The stably‐stratified outermost core revisited
Author(s) -
Lay Thome,
Young Christopher J.
Publication year - 1990
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/gl017i011p02001
Subject(s) - geology , outer core , core (optical fiber) , inner core , mantle (geology) , seismology , geophysics , physics , optics
The P‐wave velocity structure of the outermost 200 km of the outer core (the E' region) is analyzed using a suite of differential travel‐times for SKS, SKKS and S‐waves bottoming below, within, and above this depth range. Core‐penetrating phases with paths beneath Alaska exhibit similar SKS‐SKKS differential travel‐time patterns to phases sampling the core beneath the central Pacific, but very different SKS‐S differential travel‐times. These patterns can be explained by a core velocity model in which the outermost 50 to 100 km has 1–2% slower P‐wave velocities than standard Earth models, perhaps due to a stably‐stratified chemical boundary layer, combined with 3% lateral variations in S‐wave velocity in the lowermost mantle.