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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, B11304, doi:10.1029/2004JB003501, 2005

Models of lithosphere and asthenosphere anisotropic structure of the Yellowstone hot spot from shear wave splitting

Gregory P. Waite

Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah, USA


Derek L. Schutt

Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming, USA


Robert B. Smith

Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah, USA


Abstract

Teleseismic shear wave splitting measured at 56 continuous and temporary seismographs deployed in a 500 km by 600 km area around the Yellowstone hot spot indicates that fast anisotropy in the mantle is parallel to the direction of plate motion under most of the array. The average split time from all stations of 0.9 s is typical of continental stations. There is little evidence for plume-induced radial strain, suggesting that any contribution of gravitationally spreading plume material is undetectably small with respect to the plate motion velocity. Two stations within Yellowstone have splitting measurements indicating the apparent fast anisotropy direction (φ) is nearly perpendicular to plate motion. These stations are ∼30 km from stations with φ parallel to plate motion. The 70° rotation over 30 km suggests a shallow source of anisotropy; however, split times for these stations are more than 2 s. We suggest melt-filled, stress-oriented cracks in the lithosphere are responsible for the anomalous φ orientations within Yellowstone. Stations southeast of Yellowstone have measurements of φ oriented NNW to WNW at high angles to the plate motion direction. The Archean lithosphere beneath these stations may have significant anisotropy capable of producing the observed splitting.

Received 27 October 2004; accepted 8 August 2005; published 8 November 2005.

Keywords: Yellowstone; anisotropy; shear wave splitting.

Index Terms: 7208 Seismology: Mantle (1212, 1213, 8124); 7218 Seismology: Lithosphere (1236); 8121 Tectonophysics: Dynamics: convection currents, and mantle plumes; 8137 Tectonophysics: Hotspots, large igneous provinces, and flood basalt volcanism.

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Citation: Waite, G. P., D. L. Schutt, and R. B. Smith (2005), Models of lithosphere and asthenosphere anisotropic structure of the Yellowstone hot spot from shear wave splitting, J. Geophys. Res., 110, B11304, doi:10.1029/2004JB003501.