SV-wave scattering by an underwater circular cylindrical canyon in a saturated poroelastic half-space

Abstract

To study the effects of underwater terrain on plane seismic waves (P-SV wave) propagation, the theoretical solution of ground displacement, strain, rocking, and energy for the underwater terrain is derived based on Biot’s theory. Numerical results in terms of incident angle and Poisson’s ratio are illustrated for various porosities and degrees of solid frame stiffness. The results show that the response of a saturated-fluid porous soil under overlying water is controlled by the solid frame stiffness and Poisson’s ratio. Considering the effect of complex site amplification, the scattering theoretical solution of plane SV wave by a circular-arc canyon with overlying water is first derived based on the free-wave field above obtained. The effects of the incident frequencies, the incident angles, and the circular arc canyon on the ground motion of the soil-water interface are investigated parametrically. In particular, the effect of overlying water on ground motion is studied, and the results indicate that the existence of an overlying water layer absorbs the energy of a seismic wave to a certain extent. Meanwhile, the accuracy of the results is also verified by reducing the complex site to that without an overlying water layer and no canyon. Finally, based on the theoretical solution derived above, the coherence functions and the underground variable seismic motion of the site also are simulated, respectively. Compared with ground motions, the numerical results show that underground motions are smaller, which indicates that the canyon has a certain amplification effect on the seismic motions.