3-DIMENSIONAL DIFFRACTION OF COMPRESSIONAL WAVES BY A RIGID CYLINDER IN AN INHOMOGENEOUS-MEDIUM

In this paper we consider the diffraction of compressional waves by a rigid cylinder embedded in an unbounded inhomogeneous elastic medium. The point source, generating the incident pulse, is situated at a finite distance from the obstacle. It is assumed that the velocities of P and S waves are given by alpha = alpha0r(q), beta = beta0r(q) respectively, q < 1. The formal solutions of displacement field are obtained in the integral form. These integrals are evaluated asymptotically by the Residue Cagniard method to obtain the short-time estimate of the motion near the wave front in the shadow zone of the elastic medium. Numerical computations are done to investigate the behaviour of diffracted P and S waves.