Oblique Propagation of Waves in Inhomogeneous Media

The present paper deals with the propagation of plane waves travelling in an arbitrary direction through a medium the elastic parameters and density of which are a function of the vertical coordinate. Instead of describing the process by differential equations of the second order a system of linear equations is used. This procedure renders it possible to investigate the case where the movement depends in a general way on the time. A method of progressive approximation of the effect of the in-homogeneity has been worked out; this method is generally applicable with the exception of the case where the wave-normal is almost horizontal (the turning-point of a seismic ray).