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Published January 2, 2007 | Supplemental Material + Published
Journal Article Open

Evidence for a chemical-thermal structure at base of mantle from sharp lateral P-wave variations beneath Central America


Compressional waves that sample the lowermost mantle west of Central America show a rapid change in travel times of up to 4 s over a sampling distance of 300 km and a change in waveforms. The differential travel times of the PKP waves (which traverse Earth's core) correlate remarkably well with predictions for S-wave tomography. Our modeling suggests a sharp transition in the lowermost mantle from a broad slow region to a broad fast region with a narrow zone of slowest anomaly next to the boundary beneath the Cocos Plate and the Caribbean Plate. The structure may be the result of ponding of ancient subducted Farallon slabs situated near the edge of a thermal and chemical upwelling.

Additional Information

© 2007 by The National Academy of Sciences of the USA Contributed by Don V. Helmberger, October 23, 2006 (received for review May 18, 2006). Published online before print December 20, 2006, 10.1073/pnas.0609143103 This work benefited from constructive reviews by Vernon Cormier and Barbara Romanowicz and discussion with Mike Gurnis, Don Anderson, and Daoyuan Sun. We thank Alex Hutko and Thorne Lay for preprints. This work was supported by the National Science Foundation and the Natural Science Foundation of China. This is contribution no. 9164 of the Division of Geological and Planetary Sciences, California Institute of Technology. Author contributions: X. Song and D.V.H. designed research; X. Sun and X. Song performed research; X. Sun and S.Z. analyzed data; and X. Sun, X. Song, and D.V.H. wrote the paper. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/content/full/0609143103/DC1.

Attached Files

Published - SUNpnas07a.pdf

Supplemental Material - SUNpnas07asupfig10.pdf

Supplemental Material - SUNpnas07asupfig5.pdf

Supplemental Material - SUNpnas07asupfig6a.pdf

Supplemental Material - SUNpnas07asupfig6b.pdf

Supplemental Material - SUNpnas07asupfig7.pdf

Supplemental Material - SUNpnas07asupfig9.pdf


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