DIFFRACTION OF SH-WAVES BY SUBSURFACE INCLUSIONS OF ARBITRARY SHAPE

The weighted residual method was applied to the problem of scattering and diffraction of plane SH-waves by an underground inclusion of a dif ferent elastic medium and of arbitrary shape in a two-dimensional half -space. Results from the application of the weighted residual approach to the case of an underground circular inclusion closely approximate those obtained using the closed-form solution for underground inclusio ns. To demonstrate the versatility of the method, it was applied to in clusions of elliptical and square shape. It was shown that significant ground-motion amplification, with respect to the amplitude of the inc ident waves, occurred due to the presence of an inclusion or cavity. A mplifications were dependent on the size, shape, and depth of the incl usion as well as the frequency and angle of incidence of the incident waves. Amplification profiles for the lower-frequency incident waves w ere simple with peak values that did not differ significantly from 2, the value expected on the surface of a uniform half-space. As the freq uency is increased, amplification profiles become more complicated wit h worst-case values exceeding 7 for elliptical-shaped inclusions.