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利用日本K-NET与美国SEMS台网中海底强震记录研究了海底地震动特性。通过分析水平反应谱、竖向与水平加速度反应谱的比谱和弹塑性反应谱,比较了海底与陆地地震动的区别。发现海底竖向地震动的峰值加速度明显更低。在大于0.2s的周期段,海底水平地震动反应谱大于陆地谱值,而且海底谱具有更长的特征周期,并随震中距增长而增大。此外,海底地震动的竖向与水平加速度反应比谱与陆地地震动的差异很大,在小于1s的中短周期段海底地震动的比谱明显更小。根据不同的震级与震中距的真实地震动记录,提出了中等地震下不同震中距海底地震动比谱的简化设计方程。最后,比较了海底与陆地地震动的弹塑性反应谱,可知总体上海底与陆地的等延性强度折减系数谱差异不大。
The seismic behavior of the seabed was studied by using the seabed strong earthquakes recorded by K-NET in Japan and SEMS in the United States. By analyzing the horizontal response spectrum, the spectrum of the vertical and horizontal acceleration response spectrum and the elasto-plastic response spectrum, the difference between the seabed and the ground motion was compared. It is found that the peak acceleration of vertical seismic waves is significantly lower. In the period of more than 0.2s, the horizontal seismic response spectrum of seafloor is larger than the land-based spectrum, and the seafloor spectrum has longer characteristic period and increases with the increase of epicenter distance. In addition, the difference between the vertical and horizontal acceleration responses of the seabed ground motion and the ground motion is quite different. In the medium-short period of less than 1 second, the spectrum of the seabed ground motion is obviously smaller. Based on the real ground motion records of different magnitude and epicentral distances, a simplified design equation of seismic amplitude spectrum of submarine ground motions under moderate earthquakes is proposed. Finally, the elasto-plastic response spectra of seabed and terrestrial ground motions are compared. It can be seen that there is no significant difference in the intensity ductility coefficient between the bottom and the land.