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Science 6 July 2007:
Vol. 317. no. 5834, pp. 108 - 111
DOI: 10.1126/science.1141269
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Reports

Trench-Parallel Anisotropy Produced by Foundering of Arc Lower Crust

Mark D. Behn,1* Greg Hirth,1 Peter B. Kelemen2

Many volcanic arcs display fast seismic shear-wave velocities parallel to the strike of the trench. This pattern of anisotropy is inconsistent with simple models of corner flow in the mantle wedge. Although several models, including slab rollback, oblique subduction, and deformation of water-rich olivine, have been proposed to explain trench-parallel anisotropy, none of these mechanisms are consistent with all observations. Instead, small-scale convection driven by the foundering of dense arc lower crust provides an explanation for the trench-parallel anisotropy, even in settings with orthogonal convergence and no slab rollback.

1 Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
2 Lamont Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA.

* To whom correspondence should be addressed. E-mail: mbehn{at}whoi.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
The Subduction Zone Flow Field from Seismic Anisotropy: A Global View.
M. D. Long and P. G. Silver (2008)
Science 319, 315-318
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