Maximum Responses of Viscoelastic Multilayers Subjected to Inhomogeneous Plane Wave Incidence.

Abstract

The frequency response functions of the viscoelastic horizontal multilayers subjected to time harmonic plane P or SV wave incidence are generally governed by the acoustic impedance ratios of the base rock to that of each layer and by the incident angle of the waves to the layer interfaces and loss factor Q-1 of each layer. And the critical angles in the inhomogeneous wave fields play more important roles in the response characteristics than those of elastic wave fields and generalized Snell's law should be applied.In order to clarify the surface response characteristics of the viscoelastic layers, the factor termed response is introduced, which is evaluated by the ratios of the maximum surface response of viscoelastic layer in a properly chosen frequency range to that of elastic layer at the first resonant frequency in this frequency range. It was found that in the inhomogeneous wave field subjected to plane harmonic SV wave incidence, the maximum response ratio of horizontal component has eminent value at the normal incidence of SV wave, but that of vertical components has maximum value in the neighborhood of critical angles of SV wave.