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Degree‐2 pattern of attenuation structure in the upper mantle from apparent complex frequency measurements of fundamental spheroidal modes
Author(s) -
Suda Naoki,
Shibata Naoki,
Fukao Yoshio
Publication year - 1991
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 - 10.1029/91gl01337
Subject(s) - attenuation , geology , transition zone , hotspot (geology) , mantle (geology) , geophysics , upwelling , geodesy , physics , optics , oceanography
We present preliminary results of an analysis of global lateral variations in elastic and anelastic structure of the upper mantle. Using the Sompi method, we have analyzed IDA records to measure apparent complex frequencies of fundamental spheroidal modes 0 S 21 – 0 S 34 , which are primarily sensitive to the structure of the transition zone. The apparent complex frequencies have then been inverted into local frequency and attenuation maps using our new inversion method. We have obtained consistent degree‐2 patterns in the local attenuation maps as well as in the local frequency maps. The high‐attenuation anomalies correlate with regions of slow P‐wave velocity in the lower mantle and with regions of high hotspot density. This may represent a continuation of lower‐mantle upwelling into the transition zone.