More offshore structures such as sea-crossing bridges, undersea tunnels, and subsea pipelines are being constructed than ever. Owing to the lack of offshore strong motion records, onshore ground motions are used to assess the seismic behaviors of offshore structures, but onshore and offshore ground motions are significantly different from each other. In this study, the statistical characteristics of offshore strong motion records are investigated. Site factors are found to affect offshore ground motion. A comprehensive numerical analysis is then conducted to understand the influence of sloped terrain and silt soft-soil layer on offshore ground motions. The results indicate that a silt soft-soil layer on the seabed has a considerable amplification effect on the horizontal component of SV-wave. Moreover, the sloped terrain on the seabed can substantially enlarge the vertical component of P-wave.

与以往相比，正在建造更多的海上结构，如跨海大桥，海底隧道和海底管道。由于缺乏海上强运动记录，陆上地面运动被用于评估海上结构的地震行为，但是陆上和海上地面运动之间存在显着差异。在这项研究中，调查了海上强运动记录的统计特征。发现场地因素会影响近海地面运动。然后进行了全面的数值分析，以了解倾斜的地形和淤泥软土层对海上地面运动的影响。结果表明，海床上的淤泥软土层对SV波的水平分量具有相当大的放大作用。而且，