This research is to develop a better theory governing the propagation of Love and Rayleigh surface waves on a laterally heterogeneous earth model. The theory uses a slowly varying Lagrangian method to develop a JWKB theory that is then extended in a JWKB-Maslov manner to be valid near caustics, that is, near the source and antipode of the surface waves. Unlike other theories, this then will be applicable over the entire earth. The resulting computer program will be applied to the study of surface wave amplitude variations including geometric focusing and defocusing, laterally heterogeneous anelasticity, and earthquake source directivity. This research is a component of the National Earthquake Hazard Reduction Program.
