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Article
Shear Wave Splitting beneath the New Madrid Seismic Zone and Adjacent Areas
EOS Transactions, American Geophysical Union
  • Moikwathai Moidaki
  • Kelly H. Liu, Missouri University of Science and Technology
  • Stephen S. Gao, Missouri University of Science and Technology
  • John Patrick Hogan, Missouri University of Science and Technology
  • Mohamed G. Abdel Salam, Missouri University of Science and Technology
Abstract

Teleseismic shear-wave splitting parameters are determined at 15 permanent and portable broadband stations within and around the New Madrid seismic zone (NMSZ) in order to map the direction and strength of mantle fabrics and to explore the origin of seismic anisotropy. Both the splitting times and fast polarization directions of the fast shear-wave show significant spatial variations. The observed splitting times range from 0.7 to 1.7s with a mean value of 1.0s which is the same as the global average. The resulting fast directions range from 34 to 118 degrees from north with a mean of 65 degrees which is consistent with the motion direction of the North American plate in a hot-spot frame. Fast directions with ray-piercing points in the NMSZ are oblique to the rift axis. In the vicinity of the Ozarks Plateau, the split times range from 0.7s to 1.1s with a mean of 0.9s. The observed fast directions show a striking clockwise rotating pattern in which these change systematically from nearly N-S in the St. Francois Mountains to approximately NE-SW further north to be concordant to that of North American Craton. The area with anomalous fast directions has recently been suggested to be a downward asthenospheric flow as a result of the sinking of the Farallon slab in the lower mantle (Forte et al 2007). The observed anisotropy will be discussed in relation to the lower mantle flow, and the recently-proposed two-layer model of Marone and Romanowicz (2007).

Meeting Name
AGU Fall Meeting (2007: Dec. 10-14, San Francisco, CA)
Department(s)
Geosciences and Geological and Petroleum Engineering
Document Type
Article - Conference proceedings
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2007 American Geophysical Union (AGU), All rights reserved.
Publication Date
12-1-2007
Publication Date
01 Dec 2007
Disciplines
Citation Information
Moikwathai Moidaki, Kelly H. Liu, Stephen S. Gao, John Patrick Hogan, et al.. "Shear Wave Splitting beneath the New Madrid Seismic Zone and Adjacent Areas" EOS Transactions, American Geophysical Union (2007)
Available at: http://works.bepress.com/john-hogan/28/