盆地型长周期地震动的判别准则

Discriminant Criterion of Long-period Ground Motion in Basin

为了筛选出盆地内超高层结构抗震设计所需的盆地型长周期地震动(简称为长周期地震动)验算波,总结了长周期地震动的形成机理,分析了长周期地震动中面波的卓越性,提出了截取由面波主导的地震动尾波的方法,通过基于尾波特性的统计分析得到了长周期地震动的判别准则.结果表明:沉积盆地边界所激发的面波在盆地内传播、叠加以及依频率放大是长周期地震动的主要形成机理;长周期地震动中由面波主导的尾波段对长周期结构响应起控制作用;长周期地震动判别准则宜定为:速度反应谱卓越周期大于2s,且截取出的尾波与原始波在速度反应谱卓越周期处的谱幅值比大于85%.

To screen out the basin long-period ground motion inputs,which could be used for the seismic design of supper high-rise buildings in basin,the formation mechanism of long-period ground motions was explained.Then,the dominance of surface wave in long-period ground motion was analyzed,and an approach to extract the coda waves of ground motions,which were dominated by surface waves,was put forward.Finally,the discriminant criterion of long-period ground motion was proposed through statistical analysis based on the characteristics of coda waves.The results demonstrate that the propagation,overlapping,and frequency-dependent amplification of the surface waves are generated by conversion of body waves at the boundaries of deep sedimentary basins,and plains are the main formation mechanism of longperiod ground motions.The surface wave components in the coda waves of long-period ground motions are responsible for the maximum responses of long-period structures,such as supper high-rise buildings.The discriminant criterion of long-period ground motion is concluded that：the predominant period of velocity response spectrum（Tp）of ground motion is larger than 2 s,in addition,the ratio of the amplitude in the predominant period of velocity response spectrum associated with the extracted coda waves and original wave is greater than 85%.