中国大陆地区地震动时程强度包络函数研究

The study in time history envelop function of ground motion in mainland of China

地震动时程强度包络函数可描述地震动幅值的变化特征,主要用于地震安全性评价中的人工合成地震动。目前,国内工程最常用的强度包络函数参数的衰减关系是利用美国西部强震动记录统计得到的结果。本文以研究更适合我国大陆地区的强度包络函数参数及衰减关系为目标,基于中国大陆地区基岩场地强震动观测数据,采用目前广泛使用的三段式强度包络函数模型,运用70%能量持时法确定上升段持时t1和平稳段持时ts,利用统计回归方法确定衰减因子c,最终通过加权最小二乘法确定了我国基岩场地水平向和竖直向加速度时程强度包络函数参数及其衰减关系公式。通过与国内最常用的时程强度包络函数参数的衰减关系对比发现,上升段持时t1与震级之间有明显的相关性,而后者则与震级无关,下降段衰减因子c在远场普遍大于后者的研究结果。

Since time history envelope function can accurately describe the change characteristics of the seismic amplitude,it is mainly used to synthesize ground motion of seismic safety evaluation. The time history envelope attenuation relationship which has been used most generally at present was obtained statistically based on strong motion records of the western United States. In this paper,we focus on obtaining more suitable time history envelope function parameters and their attenuation relationship by using rock site records of our own country. According to the three-segment model of time history envelope function the rising duration t1 and stable duration tsare determined by the 70% energy duration method. Then the attenuation factor c is gained by means of the statistical regression method. With application of the weighted least squares method,time history envelope function parameters and theirattenuation relation formulas in horizontal and vertical direction on rock site have been derived. By contrasting those attenuation relationship with the most commonly used ones,we find that the rising duration t1 is significantly correlated to the magnitude according to our results while t1 is independent to magnitude in other relationships. Meanwhile,the attenuation coefficient c in the far field is generally bigger than the results obtained by the other relationship.