A perturbation method for elastic wave propagation: 1. Nonparallel boundaries

This is the first of a series of papers in which a small-perturbation theory for elastic wave propagation is presented. Using classical perturbation techniques, we obtain boundary conditions for the perturbation of the displacement field which, by means of the integral representation theorems of elastodynamics, permit us to express the solutions to the problems as integrals of known quantities. In this paper the method is formulated for mediums with boundaries which are slightly nonparallel. It is then applied to a study of the propagation of Love waves through a crustal layer.