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Seismic evidence for an 850 km thick low‐velocity structure in the Earth's lowermost mantle beneath Kamchatka
Author(s) -
He Yumei,
Wen Lianxing,
Zheng Tianyu
Publication year - 2014
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 - 10.1002/2014gl061249
Subject(s) - geology , core–mantle boundary , mantle (geology) , geophysics , mantle plume , shear velocity , seismic velocity , seismic wave , transition zone , seismology , tectonics , physics , lithosphere , turbulence , thermodynamics
We detect an 850 km thick low‐velocity structure in the Earth's lowermost mantle beneath Kamchatka surrounded by and overlying a 210 km thick high‐velocity D′′ structure. The velocity structure is constrained by modeling the observed anomalously broadened waveforms for seismic shear waves sampling the lowermost mantle recorded at large distances from 90° to 100°. Waveform modeling analyses reveal that the low‐velocity anomaly has a stem with a diameter of about 550 km in the lowermost 210 km of the mantle and a cap with a diameter of about 1600 km. The low‐velocity structure of the cap decreases from 0% at the top to −1.5% at about 400 km above the core‐mantle boundary (CMB) and to −1.2% at 210 km above the CMB. We suggest that the geometrical and velocity features of the low‐velocity anomaly indicate that it may represent a localized mantle plume undetected before in the lower mantle.