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Evidence for a stagnant plume in the transition zone?
Author(s) -
Vinnik Lev,
Chevrot Sébastien,
Montagner JeanPaul
Publication year - 1997
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 - 10.1029/97gl00786
Subject(s) - transition zone , plume , geology , classification of discontinuities , geophysics , core–mantle boundary , mantle plume , mantle (geology) , boundary current , seismology , oceanography , meteorology , physics , tectonics , ocean current , lithosphere , mathematical analysis , mathematics
The structure of the mantle transition zone (MTZ) beneath the Pacific ocean is investigated by using Pds waves, converted from P to S from seismic discontinuities at depths d in the receiver region. At stations within the South Pacific superswell, the pulse of P 660 s is anomalously broad. To explain this effect, we assume that the 660 km phase boundary may present a barrier for a thermochemical plume ascending from the lower mantle. Then the low‐velocity material of the plume accumulates just below this boundary, and forms a large‐scale lens, which broadens the pulse of P 660 s . The phase boundary is uplifted by heating, but the related travel time anomaly is cancelled by the increased effective width of the transition.