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Partial melting in the deepest mantle
Author(s) -
Simmons N. A.,
Grand S. P.
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 - 10.1029/2001gl013716
Subject(s) - mantle (geology) , geology , partial melting , residual , travel time , geodesy , hotspot (geology) , seismology , geophysics , mathematics , algorithm , transport engineering , engineering
We have compared the travel times of direct (P, S) and core‐reflected (PcP, ScS) phases recorded in southern Africa from earthquakes occurring in the Scotia Arc region. The low‐velocity region beneath the south Atlantic is explored by calculating ScS‐S and PcP‐P travel‐time residuals to determine the correlation and magnitude of Vs and Vp reductions in the deepest mantle. Residual calculations yield extraordinary results as PcP‐P is about 1 second larger than expected while ScS‐S is >7 seconds larger for a great circle arc distance of 54°. We investigate models of P and S velocity reductions in the deepest mantle that may explain these residuals to provide constraints on the velocity structure of the D” region in this extremely slow zone. The reductions in P and S velocity needed to match the data are consistent with partial melting in the deepest mantle for a wide range of 1D models.