Dipping low-velocity layer in the mid-lower mantle: Evidence for geochemical heterogeneity

Satoshi Kaneshima, George Helffrich

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Abstract

Data from western United States short-period seismic networks reveal a conversion from an S to a P wave within a low seismic velocity layer (greater than or equal to the 4 percent velocity difference compared to the surrounding mantle) in the mid-lower mantle (1400 to 1600 kilometers deep) east of the Mariana and Izu-Bonin subduction zones. The low-velocity layer (about 8 kilometers thick) dips 30°to 40°southward and is at least 500 kilometers by 300 kilometers. Its steep dip, large velocity contrast, and sharpness imply a chemical rather than a thermal origin. Ancient oceanic crust subducted into the lower mantle is a plausible candidate for the low- velocity layer because of its broad thin extent.

Original languageEnglish
Pages (from-to)1888-1891
Number of pages4
JournalScience
Volume283
Issue number5409
DOIs
Publication statusPublished - Mar 19 1999
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • General

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