9526606 Toomey This research involves the development of a practical tomographic method to invert teleseismic delay times simultaneously for heterogeneity and seismic anisotropy, assuming that the anisotropy is approximated by hexagonal symmetry, and to apply the method to existing data from southern California. Forward modeling calculations show that the delay time patterns associated with anisotropy alone are comparable in magnitude to delays resulting from typical upper mantle heterogeneity, underscoring the importance of including anisotropy as a free parameter in tomographic imaging. Inverse modeling of synthetic data are then used to demonstrate that a tomographic approach is feasible and stable. This work shows that a tomographic analysis of P wave data may be used to constrain variations in anisotropy with depth. This research is a component of the National Earthquake Hazard Reduction Program. ***
