This dual-institution research seeks to follow-up earlier work that demonstrated shear-wave splitting in the subcontinental mantle. It will investigate this splitting on a much more detailed scale utilizing 3-component digital equipment along a line between the western Superior province and the Black Hills in central North America. An experiment of this sort lies at the state-of-the-art in field and analysis technique, and represents the best use of PASSCAL portable instruments for study of the earth's crust and upper mantle. This research will have important application to the structure of the crust and upper mantle, and because it develops the capability for investigation of shear- wave splitting, currently believed to be an important phenomenon during the process of preparation for an earthquake, it has important application to the National Earthquake Hazard Reduction Program.
