9707189 Park This research is a collaboration between Columbia University and Yale University involving the investigation of different types of mantle heterogeneity in the stable cratonic environment of the northeastern U.S. The strong heterogeneity in this geologically old region is unexpected since lateral temperature gradients - the main cause of heterogeneity in areas of active tectonics - are probably very subdued. Travel-time anomalies correlate with shear-wave splitting variations, so at least some of the heterogeneity is probably due to lateral changes in the orientation of mantle fabrics. This research will test the hypothesis that "anisotropic domains," coherent volumes of strained mantle rock related to past tectonic activity, are the primary source of traveltime heterogeneity. The data are to come from seismograms recorded by the recent high density of fixed and portable stations in the northeastern U.S. to form a dataset of body wave traveltimes and shear wave splitting measurements. ***
