Variations of reflection and transmission coefficients at the boundaries of different media and types of contact between media

Abstract

Wave amplitudes and amplitude ratios between different wave types carry information about variations of medium properties with depth and time. The most information is contained in the reflection and transmission coefficients, which depend on the physical properties of contacting media and boundary conditions. In this paper, the range of variations in reflection and transmission coefficients of plane waves generated at boundaries with different properties is examined. Numerical simulations of coefficients were carried out for the models of rigid and non-rigid contact between isotropic and anisotropic media. At the rigid contact between isotropic media, amplitudes of generated waves and their ratios vary within relatively narrow limits while the physical parameters of the media may accept various reasonable values. In anisotropic media, coefficients depend not only on the slowness contrast, but also on the wave polarization directions, which may vary considerably in space. Amplitude ratios of generated waves may vary significantly with the incident angle, and the amplitudes of converted waves may dominate or be comparable with monotype waves. Introducing non-rigid contact between media considerably broadens the range of coefficient variations. In contrast to the rigid contact, the incident energy goes predominantly into reflected and converted waves. The amplitude of converted waves may be relatively large and exceed the amplitudes of monotype and incident waves. In general, reflection and transmission coefficients generated at non-rigid contact depend on the values of stiffness coefficients and their ratio.