Shear-Wave Splitting and Implications for Mantle Flow Beneath the MELT Region of the East Pacific Rise

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Science  22 May 1998:
Vol. 280, Issue 5367, pp. 1230-1232
DOI: 10.1126/science.280.5367.1230

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Shear-wave splitting across the fast-spreading East Pacific Rise has been measured from records of SKS and SKKSphases on the ocean-bottom seismometers of the Mantle Electromagnetic and Tomography (MELT) Experiment. The direction of fast shear-wave polarization is aligned parallel to the spreading direction. Delay times between fast and slow shear waves are asymmetric across the rise, and off-axis values on the Pacific Plate are twice those on the Nazca Plate. Splitting on the Pacific Plate may reflect anisotropy associated with spreading-induced flow above a depth of about 100 km, as well as a deeper contribution from warm asthenospheric return flow from the Pacific Superswell region.

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