## 1 Introduction  
In recent years, due to the increasing development of maritime transportation in China, the construction of marine engineering has become the focus of China's development [1, 2, 3]. At the same time, the South China Sea is located in a complex geological environment with active ground motion. As an important basis for seismic design and seismic safety evaluation of marine engineering, seismic response analysis of sea areas should be highly concerned [4, 5, 6]. The study of site seismic response is started from the land area. The seismic response analysis of land sites involves the nonlinear constitutive relationships of soil, the distribution of soil layers, and the boundary conditions. The earlier deterministic site seismic response analysis method is the linear elastic wave analysis method, which assumes that the soil is a linear elastic medium. [PERSON] [7], [PERSON] [8], and [PERSON] [9] used analytical and semi-analytical methods to study the seismic response of the semi-circular and semi-elliptical valley site under the incident plane SH wave. [PERSON] et al. [10] performed a numerical experiment using the finite element method, exploring the combined effect of wave passage and the presence of 2D topographic features. To further consider the nonlinear constitutive relationship of soil, [PERSON] et al. [11] proposed a new generation of one-dimensional site seismic response calculation method and the computer program SOILQUAKE and tested the program by using actual seismic records of four types of sites with extremely thick cover-layers. Since then, [PERSON] et al. [12], [PERSON] and [PERSON] [13], [PERSON] et al. [14], [PERSON] et al. [15], and [PERSON] et al. [16] have carried out further research work. For the boundary conditions of the soil, the viscous boundary proposed by [PERSON] and [PERSON] [17] is more accurate in a one-dimensional case, but it is prone to low-frequency drift in other cases. [PERSON] and [PERSON] [18] derived a two-dimensional viscoelastic artificial boundary based on the cylindrical wave equation. [PERSON] et al. [19] proposed the three-dimensional viscoelastic artificial boundary through the spherical wave equation and further derived the viscoelastic artificial boundary with the unity of dynamic and static. [PERSON] and [PERSON] [20] presented the first developed site amplification model for Croatia using random vibration theory. [PERSON] et al. [21] used PLAXIS3D software to numerically simulate the liquefaction effect on soil-structure interaction under earthquake action. [PERSON] et al. [22] presented the local site amplification maps for the volcanic area of Trecastagni, south-eastern Sicily, in Italy. The seismic response analysis of islands and reefs is still in the initial stage because of the complexity of the problems. [PERSON] et al. [23] developed FSSI-CAS 3D, a numerical analysis model of fluid-structure-foundation dynamic interaction based on the finite volume method, and took caisson breakwater as an example to study the dynamic interaction among ocean waves, caisson breakwater, and seabed foundation. [PERSON] et al. [24] established a 2D seismic response analysis model for coral reefs by considering the nonlinear dynamic characteristics of coral sand and the influence of artificial boundary conditions at the near-field site. They analyzed the spatial distribution characteristics of the peak acceleration amplification factor, ground surface acceleration response spectrum, and time-holding characteristics of the reef site, but they did not consider the influence of seawater on the seismic response of the reef site in the analysis. [PERSON] et al. [25] proposed two novel parallel implicit black-box coupling algorithms for partitioned fluid-structure interaction simulations. The simultaneous calculation of fluid and structure overcomes the parallel efficiency limitations of the classical staggered coupling approaches if used on massively parallel systems. [PERSON] et al.