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Scales of heterogeneity near the core‐mantle‐boundary
Author(s) -
Lavely Eugene M.,
Forsyth Donald W.,
Friedemann Phyllis
Publication year - 1986
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/gl013i013p01505
Subject(s) - geology , mantle (geology) , residual , core–mantle boundary , transition zone , shear velocity , geophysics , anomaly (physics) , geodesy , seismology , meteorology , geography , physics , algorithm , condensed matter physics , computer science , turbulence
We have mapped shear velocity variations near the base of the mantle with ScS‐S differential travel times. Beneath the North Atlantic, there is a systematic variation in velocity over a distance of 1500 km or more, with a pronounced low velocity anomaly centered roughly beneath Madeira island. Beneath the northern Indian Ocean, there is no similar long‐wavelength anomaly. The average ScS‐S residual beneath the Indian Ocean is 3.6 ± 0 .7 s more negative than the Atlantic residual, indicating faster average velocities near the base of the mantle.