近断层强地震地面运动特征参数分析

摘要

102 strong ground motion records within the rupture distance of 100 km during the Wenchuan earthquake were selected to study that whether intensity measures of ground motions could describe the characteristics of near⁃fault earthquake⁃induced ground motions. Both time⁃history curves and response spectrums were performed to study the intensity measures of ground motions and the characteristics of spectrum parameters in different rupture distances.Results showed that the ratio of horizontal and vertical peak ground velocity to acceleration could not represent the intensity measure of near⁃fault ground motions.Also,the choosing value standard within 1/2⁃2/3 of ratio of peak acceleration in vertical and horizontal motions ( PVA/PHA ) was not suitable for near⁃fault motions. In contrast to the horizontal acceleration spectrums, more high frequencies were obtained in vertical spectrums which presented the narrow shape and the smaller characteristic period. With the increasing rupture distances, the average vertical acceleration spectrum attenuated more rapidly. It is recommended that the βmax in code design spectrum should give a reasonable increase for near⁃fault earthquake⁃induced ground motions.%针对以往用于描述一般地震动的强度表征参数是否也适用于近断层强地震动的问题，筛选出汶川地震中断层距100 km内的102条强震记录，通过时程曲线和反应谱分析，研究各类地震动强度指标及其谱参数特性随断层距的变化规律。结果表明：水平向及竖向的峰值速度与峰值加速度比不适合作为近断层地震动的强度表征参数，且竖向与水平向峰值加速度比为1／2～2／3的公认取值标准不适用于近断层地震动的情况。反应谱分析中，竖向加速度反应谱较水平向反应谱包含更多的高频成分，且谱形窄，特征周期明显较小。随着断层距的增加，竖向加速度平均反应谱衰减速度更快。针对近断层地震动，规范设计谱的平台值（βmax ）应适当增大，以提高安全储备。