The influence of seabed on offshore ground motion

The characteristics between offshore and onshore ground motions are different based on the complex geological structure of the seabed. But the influence of seabed topography on the characteristics of offshore ground motions is less studied. Therefore, in order to analyze the influence of site conditions, local site topography and other factors on the characteristics of offshore ground motion, a numerical simulation method for the propagation process of offshore ground motion is proposed by combining the self-designed wave analysis program and the finite element dynamic analysis software. Firstly, different numerical models including canyon, ridge and slope are constructed to analyze the effect of different topography on the characteristics of the offshore ground motion. Besides, the influence of the seawater layer, the incidence angle of ground motion and the soft soil layer is also analyzed. Finally, a complex seabed site model is established to study the effects of different topographic coupling on the offshore ground motion. The seismic response of offshore slope, ridge and canyon site will be significantly amplified by P wave, and it is found that the seismic response is particularly enhanced at the inflection point of all kinds of topography. However, the effect of different topography on SV wave seismic response is limited. In addition, the water depth and the slit soft soil layer also affect the seismic response of the seabed site.