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Published May 29, 2007 | Supplemental Material + Published
Journal Article Open

Seismological support for the metastable superplume model, sharp features, and phase changes within the lower mantle


Recently, a metastable thermal-chemical convection model was proposed to explain the African Superplume. Its bulk tabular shape remains relatively stable while its interior undergoes significant stirring with low-velocity conduits along its edges and down-welling near the middle. Here, we perform a mapping of chemistry and temperature into P and S velocity variations and replace a seismically derived structure with this hybrid model. Synthetic seismogram sections generated for this 2D model are then compared directly with corresponding seismic observations of P (P, PCP, and PKP) and S (S, SCS, and SKS) phases. These results explain the anticorrelation between the bulk velocity and shear velocity and the sharpness and level of SKS travel time delays. In addition, we present evidence for the existence of a D" triplication (a putative phase change) beneath the down-welling structure.

Additional Information

© 2007 by the National Academy of Sciences. Edited by Russell J. Hemley, Carnegie Institute of Washington, Washington, DC, and approved March 7, 2007 (received for review September 15, 2006). Published online before print April 10, 2007, 10.1073/pnas.0608160104 We thank two anonymous reviewers for helpful discussion and comments, which improved this article. The waveform data were obtained from Incorporated Research Institutions for Seismology. This work was supported by National Science Foundation Grant EAR-0456433. Author contributions: D.S. performed research; E.T., D.H., and M.G. contributed new reagents/analytic tools; and D.H. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/cgi/content/full/0608160104/DC1.

Attached Files

Published - SUNpnas07b.pdf

Supplemental Material - SUNpnas07bsuppfig10.pdf

Supplemental Material - SUNpnas07bsuppfig11.pdf

Supplemental Material - SUNpnas07bsuppfig7.pdf

Supplemental Material - SUNpnas07bsuppfig8.pdf

Supplemental Material - SUNpnas07bsuppfig9.pdf

Supplemental Material - SUNpnas07bsupptext.pdf


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