To identify signals passing through solid rock, generated by powerful sources of vibration, in various aspects of practical geodynamics and in solving questions of protection of engineering structures (buildings, pipelines, tunnels, etc.) from seismic waves and pulsed loads, it is very useful to have information on the fundamental properties of the propagation of elastic waves in inhomogeneous and stratified media, composites, and compound structures and systems.One of the simplest models of a compound (stratified) medium is an inffmitely long layer in contact with elastic media. As some limiting cases of this model we can consider the following, a) The media adjoining the upper and lower surfaces of the layer have the same physical characteristics; b) one medium is absent (the corresponding surface of the layer is free from stresses); c) either the layer or one of the media has zero shear strength (an ideal compressible liquid); d) an elastic layer is immersed in a liquid; e) a layer is compressed between absolutely rigid bodies.The problems also differ in the conditions of contact between the layer and the medium-rigid contact (stresses and displacements equal); sliding contact (no shear resistance in the plane of contact); and various types of elastic contact (we have in mind the presence of a linear elastic bond between the layer and the medium).A fairly extensive bibliography has now accumulated on the existence and description of various types of free waves propagated in a system. This work was begun by Bromwich [1] and Love [2], who discussed longwave and short-wave approximations respectively (since the only linear dimension here is the thickness of the layer, the wavelength is referred to it). Among investigations of the dynamic of stratified media, Brekhovskikh [3] gives the dispersion characteristics of the first few modes of a plane homogeneous layer with surfaces free from stresses. Further investigations were devoted to the properties of the dispersion equations and the construction of the phase curves for various wave modes (a fairly complete survey of this work can be found in [4]).in the USSR, various methods of solving dynamic problems of this type have been successfully developed by the Lenin_grad school (G. I. Petrashen', L. A. Molotkov, K. I. Ogurtsov, G. I. Marchuk, E. I. Shemyakin, and others). In a monograph, describes completed investigations of a number of fundamental aspects of the theory of wave propagation in strata, describes the conditions of existence of various groups of waves (mainly surface waves) in relation to the parameters of the strata, and studies wave perturbations in each particular case. He gives references up to 1960.With the advent of high-speed computers, solution of the dispersion equations became a purely technical problem. A great deal of information has now accumulated concerning the properties of the phase curves for various relations between the parameters of the layer and the medium (see, e~., [6][7][8][9][10])o For a layer on a half space (with sliding cont...