Seismic response of reef-seawater system with steep slope under Scholte wave

Abstract

The topographic feature of offshore reef leads to its unique response under earthquakes, especially considering the influence of surface waves. A dynamic solid-fluid coupling numerical model is developed to analyze the seismic response of reef-seawater system with steep slope under the Scholte wave, a special type of surface wave observed in submarine earthquakes. The governing equations, dispersion equation, and motion of steady Scholte wave are deduced. For transient Scholte wave, a non-uniform seismic wave input method for numerical analysis is proposed utilizing a novel stepwise artificial boundary condition (S-ABC). Using the proposed seismic input method, the seismic response of a typical reef-seawater system is analyzed. From the numerical results, shear wave is found to be partly dissipated by seawater. On the contrary, seawater can significantly amplify the motion of Scholte wave at the reef flat. The influence of topographic features, including flat width, height, and slope angle, are found to be limited for shear wave, but remarkable for Scholte wave. The findings suggest that amplification effect of seawater on surface waves and the influence of topographic features must be considered for the seismic response of offshore reefs.