Two primary goals of seismic reflection processing are: (1) to image geologic structure and (2) to provide information about lithology for interpretation. The process used to achieve the second goal is made complex by the fact that the same seismic velocity may result from several different combinations/mixtures of materials in the earth. It is therefore necessary to explore the possible range of seismic velocities that can occur within the set of circumstances deemed most likely to occur in the earth at the site of interest.
Fine horizontal layering (i.e., layers with thickness small compared to the wavelength of the seismic wave) is known to result in vertical transverse isotropy (VTI) - wherein wave speeds vary with angle in such media, but are uniquely determined by the angle from the vertical. There has continued to be some doubt about the range of anisotropy parameters possible in such media. Here I will correct an error of Postma (1955) and show that the P-wave anisotropy parameter c11/c33 can be a factor of 2 smaller than previously supposed. I also obtain a simple upper bound on this parameter in terms of layer elastic parameters.