Abstract
Reef islands are valuable terrestrial resources for ocean exploitation and utilization but face the serious threat of earthquake disasters. This study takes Zhubi Reef in the South China Sea as the research object and establishes a three-dimensional (3D) reef-seawater model to investigate the seismic response of Zhubi Reef. The 3D local topography and the effect of fluid-solid interaction are comprehensively considered. The artificial boundaries of fluid and solid domains are adopted to simulate the wave radiation and absorption of the semi-infinite seabed and the infinite seawater layer. The boundary substructure method is used to input the seismic waves into the numerical reef models. The results indicate that the seismic responses, including the peak values of the ground motions and the acceleration response spectra, are significantly amplified over Zhubi Reef. The acceleration response spectra on the reef flat shift closer towards the low-period direction compared with those of the seismic waves input from the subsea bedrock. In addition, the 3D topographic effect on the seismic response of Zhubi Reef is studied through a comparative analysis between two-dimensional (2D) and 3D reef models. The distribution laws of the peak response in the middle region of the reef flat calculated by the 2D and 3D models agree well with each other, and the differences are obvious in the edge areas where the local 3D topographies change drastically.
Highlights
With technological progress and economic development, the exploitation and utilization of the ocean have entered a new stage
In the previous studies completed by our research team, we comprehensively considered the abovementioned key factors and established a seismic analysis model of reef islands [13]. e artificial boundaries of fluid [14] and solid [15] media are applied on the truncated boundary of the near-field model to simulate the wave radiation effect, and the seismic wave input method based on the substructure of artificial boundaries [16] is adopted to realize the incidences of seismic P and SV waves at different angles in the reef models. en, a typical reef island in the South China Sea, namely, Yongshu Reef, is taken as a research object, and its ground motion field distribution and seismic response characteristics are studied through 2D and 3D analysis [17, 18]
It is important to provide the local response spectra on the reef flat when conducting the seismic design on those reef constructions. erefore, we further investigate the spatial distribution of acceleration response spectra along the reef flat of Zhubi Reef. e calculated acceleration response spectra with the damping factor of 5% are plotted on 3D images as shown in Figure 10, with the period and the normalized parameter x/L as horizontal coordinates
Summary
With technological progress and economic development, the exploitation and utilization of the ocean have entered a new stage. Chen et al [10] considered the nonlinear dynamic characteristics of coral sand and the influence of the infinite foundation, established a 2D seismic analysis model of coral reefs with a height of 20 m, and analyzed the spatial distributions of the ground motion field and the response spectrum on reef flats. En, a typical reef island in the South China Sea, namely, Yongshu Reef, is taken as a research object, and its ground motion field distribution and seismic response characteristics are studied through 2D and 3D analysis [17, 18]. Is study takes Zhubi Reef as the research object, comprehensively considers the 3D local topographic characteristics, the effect of fluid-solid interaction, the wave radiation effect of the semi-infinite seabed and the infinite seawater layer, and the seismic wave input method, and establishes a 3D reef-seawater system model to investigate the distribution of the seismic wave field on Zhubi Reef. The 3D topographic effect on the seismic response of Zhubi Reef is studied through a comparison analysis between the 2D and 3D reef models
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