Abstract: According to the epicenter distance and the site classification, the 404 groups of earthquake recordings of the main shock of Chi-Chi, Taiwan, China earthquake in 1999 are sorted out in this paper. Based on these data, we analyze the statistic features of duration, PGA, envelopes and response spectra ratio of horizontal and vertical component of the acceleration recordings. The results of analyses show that the effect of site classification on characteristics of various components in acceleration time history is obvious; furthermore, fault direction also has certain effects on the characteristics of horizontal component of ground motion acceleration. The detailed research results are: 1) the duration of horizontal component of acceleration records increases with the softening of site; 2) the direction of fault slip has some effects on PGA’s attenuation features; 3) the average envelopes of acceleration records at different distances and site class basically are single peak functions of time and the envelopes of horizontal and vertical components of ground motion are obviously different; 4) with the same epicenter distance, EW/SN response spectrum ratios tend to approximate to 1.0 as site becomes softer and period shorter. V/H response spectrum ratios in short periods (<0.1s) increase with the softening of site, however, V/H ratios within long-period range (>characteristic period) decrease with the softening of site, and the decrease of V/EW ratio speeds up relatively.

Key words: site, duration, envelope, response spectrum ratio

摘要： 文中将921台湾集集地震主震的404组强震记录按照不同震中距和场地类别分组,对加速度水平分量和垂直分量的持时、峰值加速度(PGA)、包络线、反应谱比值进行了统计分析。结果表明,场地条件对不同分量加速度时间历程的若干特征有显著的影响,而且比较复杂。此外,断层方向对地震动水平特性也有一定的影响。具体研究结果为:1)地震动水平分量的持时随着场地依次变软而增大;2)断层方向对PGA衰减特征有一定影响;3)不同震中距离和场地条件下集散的时间里程的包线基本上都是单峰点的时间函数;地震动加速度水平分量包络线与竖向分量包络线有明显的不同;4)在震中距相同的条件下,场地愈软弱,周期愈短,谱比值EW/SN愈接近1。场地愈软,在短周期(<0.1s)段,V/H谱比值是变大的趋势,而在长周期(>特征周期)段则是变小的趋势;而且相对来说V/EW谱比值随场地变软而减小的趋势相对要强一些。

关键词: 场地, 持时, 包络线, 反应谱比值