The Effect of the Density Ratio at a Boundary on the form of the Spectral Response of a Thin Layer

Abstract

In recent years, theoretical calculations of the amplitudes of waves of various types, of the spectral response of layers, and so on for specific experimental conditions have been used frequently in interpreting seismic data. The principal desire has been the determination of the seismic properties of the section: the thickness of individual layers and the propagation speeds for elastic waves within these layers. Usually, the densities of the rocks are not considered in such calculations. The reason for this is that information about densities is normally not available in areas where seismic exploration is being done. As a consequence, the density ratio ρ_k/ρ_{k ± 1} boundary is usually assumed to be unity in the calculations. In fact, though, it is well known that rocks which differ in age or lithology also differ in density. Actually, the range of relative change in the density of various media is considerably smaller than the range of relative change in wave speeds for the same rocks.