川滇地区水平向强地震动衰减关系研究

Research on attenuation relationships for horizontal strong ground motions in Sichuan--Yunnan region

利用近几年在川滇地区破坏性地震及汶川地震强余震中获得的951条加速度记录,通过选取合适的衰减关系形式和距离参数,经统计获得了川滇地区水平向峰值加速度与35个周期点对应的加速度反应谱(阻尼比0.05)衰减关系.统计结果显示,震级越大,地震动随距离的衰减越慢;加速度反应谱的短周期部分随距离的衰减明显快于长周期部分;中强地震在近场也会产生较大的峰值加速度和较高的短周期加速度反应谱.由于统计资料的非完整性,本文统计结果尚不宜直接应用于相关工程场地的设计地震动参数确定中.但本文结果与目前由转换方法得到的我国西部地震动参数衰减规律的较大差异提示:进一步深入研究我国地震动参数衰减规律应是紧迫而重要的任务.

By statistical analyses of 951 sets of acceleration records obtained in several destructive earthquakes and aftershocks of Wenchuan Ms8. 0 earthquake, the attenuation relationships for peak ground acceleration （PGA） and acceleration response spectra （damping ratio 0.05） in Sichuan-Yunnan region of China were determined with appropriate attenuation relationship formula and distance parameters. The result of this study indicates that the ground motion induced by larger earthquakes attenuated much slower with the increase of distance than that induced by smaller ones, and the acceleration response spectra for shorter periods （0--0. 15 s） attenuated more quickly with the increase of distance than that for longer periods （0.2--10 s）, which were the two reasons why considerably large PGA and short-period spectrum acceleration were commonly observed in near-field of moderate earthquakes. But these attenuation re- lationships could not be used in the determination of design ground motion for engineering sites because of the data incompleteness. The significant difference between the result of this study and the attenuation relationship law in western China obtained with conversion method indicates that further research on the at- tenuation relationship laws in China is an important and pressing task.