Seismic response analysis of the reef-seawater system under obliquely incident P and SV waves

Abstract Despite the increasing focus on the seismic safety of reef engineering sites, the current studies on this topic are still based on the hypotheses of uniform seismic excitations or the vertical incidence of seismic waves. In this study, a two-dimensional seismic analysis model for the reef-seawater system under obliquely incident P and SV waves is developed, which considers the fluid-soil-interaction and the wave radiation effects of the fluid and the solid domain. The oblique input of the seismic wave into the reef-seawater model is accomplished through the boundary substructure method. A series of parametric studies are conducted, the ground motion fields on the reef sites are discussed, and the effects of several fundamental factors on the seismic response are comprehensively studied. The results show that under most circumstances, the least favorable load case for the reef site seismic response is the vertical incidence of seismic waves. However, for the horizontal ground motion of the reef site under the P wave, the least favorable incident angle is approximately 30°. In addition, the largest horizontal seismic response usually appears near the downstream side of the reef flat, and the peak velocity and acceleration ratios can reach up to 4 in this area.