Unphysical negative values of the anelastic SH plane wave energy-based transmission coefficient

Shahin Moradi, Edward S. Krebes

Computing reflection and transmission coefficients in viscoelastic media is complicated since proper signs have to be chosen for the vertical slowness of the scattered waves. Research has shown that the commonly used methods for deciding the sign of the vertical slowness in the elastic media do not produce satisfactory results in viscoelastic case. New methods have been suggested by researchers to solve the problem, but none of them are quite perfect since some undesirable results still exist in these methods. ERC or the Extended Radiation Condition suggested by Krebes and Daley (2007) is one of the methods that give reasonable results. It has been found that when ERC is used, in some cases, the energy-based transmission coefficient becomes negative in a specific range of supercritical angles. In this work the conditions under which T becomes negative is determined and examined with numerical examples. It will be shown that only for the case in which V2 > V1 and Q2>Q1, under specific conditions T is negative for specific range of supercritical incidence angles.