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Mid-mantle deformation inferred from seismic anisotropy

Wookey, J., Kendall, J.M. and Barruol, G. (2002) Mid-mantle deformation inferred from seismic anisotropy. Nature, 415 (6873). pp. 777-780. ISSN 0028-0836

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Abstract

With time, convective processes in the Earth's mantle will tend to align crystals, grains and inclusions. This mantle fabric is detectable seismologically, as it produces an anisotropy in material properties—in particular, a directional dependence in seismic-wave velocity. This alignment is enhanced at the boundaries of the mantle where there are rapid changes in the direction and magnitude of mantle flow, and therefore most observations of anisotropy are confined to the uppermost mantle or lithosphere and the lowermost-mantle analogue of the lithosphere, the D" region. Here we present evidence from shear-wave splitting measurements for mid-mantle anisotropy in the vicinity of the 660-km discontinuity, the boundary between the upper and lower mantle. Deep-focus earthquakes in the Tonga–Kermadec and New Hebrides subduction zones recorded at Australian seismograph stations record some of the largest values of shear-wave splitting hitherto reported. The results suggest that, at least locally, there may exist a mid-mantle boundary layer, which could indicate the impediment of flow between the upper and lower mantle in this region.

Item Type: Article
Copyright, Publisher and Additional Information: © 2002 Macmillan Magazines Ltd
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds)
Depositing User: Repository Officer
Date Deposited: 20 Sep 2004
Last Modified: 04 Jun 2014 09:59
Published Version: http://www.nature.com/nature/
Status: Published
Refereed: Yes
Identification Number: 10.1038/415777a
URI: http://eprints.whiterose.ac.uk/id/eprint/78

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