Seabed seismic analysis using exact responses of solid-liquid free field for 2D oblique incident waves by finite/infinite element method

Abstract

The seabed seismic analysis of a viscoelastic half-space with overlying liquid under two-dimensional (2D) oblique incident P- or SV-waves is performed by the finite/infinite element method (FIEM). Firstly, the exact solutions of the free-field solid-liquid responses in frequency domain are derived for the waves with arbitrary incident angles, including the critical angles of reflection for SV-waves and of transmission for P- and SV-waves. Next, the equivalent seismic forces to be imposed on the near-field boundaries are computed for the solid and liquid assuming that the earthquake data are available on the solid-liquid interface. Then, the equations of motion for the seabed modeled by the finite/infinite elements are presented with the solid-liquid interface implemented and the key parameters selected. The reliability of the solutions has been verified by comparison with Wolf's in frequency domain, and by inversely computing the input ground motions in time domain. New findings from this paper include: (1) The suppressive frequencies exist in the presence of overlying liquid, for which the vertical solid displacements are reduced for P- and SV-waves both for under-critical cases. (2) Both the horizontal and vertical displacements of the solid surface are reduced by overlying liquid for SV-waves with over-critical incident angles.