Introduction

Seismic anisotropy is required for a correct interpretation of the retrieved S-velocity structure in tomographic studies at least in the first 400 km of the upper mantle (Gung et al., 2003). A detailed knowledge of the seismic anisotropic structure of the earth's mantle also provides insight into debated geophysical issues, such as the nature and strength of the lithosphere/asthenosphere coupling, the depth extent of continental sub-regions and the relation of imaged seismic anisotropy to present-day asthenospheric flow and/or past tectonic events recorded in the lithosphere.

To date, our knowledge of the North American anisotropic structure arises mainly from global tomographic models (e.g. Ritsema et al., 1999; Gung et al., 2003) or SKS splitting studies (e.g. Fouch et al., 2000; Savage and Sheehan, 2000), which lack horizontal and vertical resolution respectively, and are limited to either radial or azimuthal anisotropy.

Our goal is a new high resolution model for the North American upper mantle incorporating both radial and azimuthal anisotropy. We aim at unprecedented lateral and depth resolution by improving both data coverage and methodology.

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