Start |Author Index | View Uploaded Presentations | Meeting Information

North-Central Section (44th Annual) and South-Central Section (44th Annual) Joint Meeting (11–13 April 2010)

Paper No. 4
Presentation Time: 2:30 PM

MANTLE ANISOTROPY BENEATH THE NEW MADRID SEISMIC ZONE AND ADJACENT AREAS


MOIDAKI, Moikwathai, Physics, University of Botswana, Gaborone, Botswana, GAO, Stephen S., Geological Sciences and Engineering, Missouri University of Science and Technology, Rolla, MO 65409, LIU, Kelly H., Geological sciences and engineering, Missouri university of science and technology, 129 McNutt Hall, Rolla, MO 65409 and ATEKWANA, Estella, Boone Pickens School of Geology, Oklahoma State University, Noble Research Center, Stillwater, OK 74078, moidaki@mopipi.ub.bw

A total of 93 well-defined PKS, 54 SKKS, and 126 SKS shear-wave splitting parameters are determined at 25 broadband seismic stations in an approximately 1000 by 1000 km2 area centered at 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. Unlike most previous shear-wave splitting studies which suggested uniform station-averaged splitting parameters (fast direction and splitting time) in the same area, our results, when presented in the form of individual (instead of station-averaged) splitting parameters and used the PKS, SKKS in addition to SKS phases, suggest significant and systematic spatial and azimuthal variations in the splitting parameters. The azimuthal variations at most stations can be best explained as the combinedeffects of present SW-NE-ward asthenospheric flow related to the motion of the North American plate in a hot-spot reference frame, and the NNE trending lithospheric fabrics formed during past orogenic events. In the NMSZ, anticipated rift-parallel fast directions associated with vertical magmatic dikes or along-rift flow, rift-orthogonal fast directions from small-scale convection, or reduction in splitting times as a result of vertical asthenospheric flow are not observed, suggesting that the NMSZ is a shallow feature which is consistent with results from other geophysical studies such as seismic reflection surveys. Due to the large spacing between the stations, the boundaries between the areas with different characteristics of splitting parameters cannot be decided accurately, and consequently the correlation between the splitting parameters and results from other geological and geophysical studies cannot be uniquely determined. The upcoming Transportable Array stations will greatly improve the spatial resolution of the anisotropy measurements, and thus will most likely lead to more insights to the structure and dynamics of the NMSZ.

Session No. 2

T1. Lithospheric Structure of the Mid-Continent Region: What We Know, What We Need to Know, and What EarthScope Can Tell Us
Sunday, 11 April 2010: 1:30 PM-3:15 PM
Compton Ferry (Branson Convention Center)
Geological Society of America Abstracts with Programs. Vol. 42, No. 2, p.38
© Copyright 2010 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
Back to: T1. Lithospheric Structure of the Mid-Continent Region: What We Know, What We Need to Know, and What EarthScope Can Tell Us
<< Previous Abstract | Next Abstract >>