This research is to deploy 20 three-component broadband seismometers, most of which will come from the PASSCAL program, to study variation in the physical properties of the crust and upper mantle beneath the eastern Snake River Plain region. This region shows the results of a mantle hot spot crossing the continent with associated volcanic and earthquake activity. Tomographic imaging of the P- and S-wave velocities and attenuation will be used to outline the thermal and partial melt structure of the hot spot plume in the crust and upper mantle. Shear-wave splitting will be used to study anisotropy and implied mantle flow structure. This research is a component of the National Earthquake Hazard Reduction Program.