海底与陆地地震动反应谱比定量分析

为了研究海底地震动与陆地地震动反应谱统计特性的差异,选取日本相模湾地区K-net的922组海底地震动记录和KiK-net的4599组陆地地震动记录,通过对海底与陆地地震动标准化弹性加速度反应谱以及弹塑性反应谱的对比分析表明:弹性反应谱的海陆谱比变异较小,平均值可作为定量对比关系;当周期小于0.5 s时海域与陆地地震动的差异较小,当周期0.5 s以上时海域与陆地地震动反应谱的差异明显,海域地震动的竖向分量显著较小;对于等强度延性谱,当震级或震中距较小时,有必要考虑1.5 s及以上周期的水平方向海底与陆地地震动的差别;而对于竖向地震动,则需更加关注0.5 s以下短周期地震动的海底与陆地地震动的差异。

Quantitative analysis on the difference of spectral ratios between offshore and onshore ground motions

To study the difference of the statistical characteristics of response spectrums between offshore and onshore ground motions,922 sets of offshore records of K-net and 4599 sets of onshore records of KiK-net in the Sagami Bay region in Japan were selected.The comparison and analysis of the standardized elastic response spectra and the elastoplastic response spectra of the offshore and onshore ground motions show that:the coefficients of variation of averaged response spectra are small,it is reasonable to take the average value as a quantitative comparable parameter.When the spectral period is less than 0.5 s,the difference between the response spectra of offshore and onshore ground motions is rather small.When the period is longer than 0.5 s,the difference is obvious,and the vertical component of the offshore ground motion is significantly smaller.For the constant-strength ductility spectra,when the seismic magnitude or epicentral distance is small,it is necessary to consider the difference between the horizontal components of offshore and onshore ground motions with spectral period above 1.5 s.For the vertical ground motion,it is necessary to pay more attention to the difference between offshore and onshore ground motions with spectral period below 0.5 s.