Theoretical results in the previous chapter predict that plane harmonic waves reflected and refracted at plane anelastic boundaries are in general inhomogeneous with the degree of inhomogeneity dependent on the angle of incidence, the degree of inhomogeneity of the incident wave, and properties of the viscoelastic media. As a result physical characteristics of the waves such as phase velocity, energy velocity, phase shifts, attenuation, particle motion, fractional energy loss, direction and amplitude of maximum energy flow, and energy flow due to wave interaction vary with angle of incidence. Consequently, these physical characteristics of inhomogeneous waves propagating in a stack of anelastic layers will not be unique at each point in the stack as they are for homogeneous waves propagating in elastic media. Instead these physical characteristics of the waves will depend on the angle at which the wave entered the stack and hence the travel path of the wave through previous layers. Towards understanding the significance of these dependences of the physical characteristics on angle of incidence and inhomogeneity of the incident wave, numerical models for general SII and P waves incident on single viscoelastic boundaries are presented in this chapter. Study of this chapter, especially the first three sections, provides additional insight into the effects of a viscoelastic boundary on resultant reflected and refracted waves.

A computer code (WAVES) is used to calculate reflection–refraction coefficients and the physical characteristics of reflected and refracted general waves for the problems of general (homogeneous or inhomogeneous) plane P, SI, and SII waves incident on a plane boundary between viscoelastic media (Borcherdt et al., 1986).