基于NGA模型的芦山余震地震动衰减关系

Ground Motion Attenuation Relationship of Lushan Aftershocks Based on NGA Model

四川省芦山县于2013年4月20日发生了7.0级地震,基于国家强震动台网中心发布的此次地震的2106组余震强震动记录,利用基于NGA衰减关系的简化模型,使用随机效应方法拟合得到其PGA以及0.01~8 s周期下的伪加速度反应谱(阻尼比5%)的地震动衰减关系。与其他学者研究得出的四川其他地区衰减关系进行对比,本文模型能够较好地预测芦山余震强震动衰减。不论基岩场地和软土场地,本文在衰减关系在短周期均与卢大伟模型结果一致。但是在长周期情况下,本文模型在软土场地大于卢大伟结果,而在基岩场地上低于俞言祥结果。因此,在使用本文衰减关系时,要特别注意场地和周期对其的影响。

On April 20,2013,and the M7 earthquake occurred in Lushan county,Sichuan Province.Based on the 2106 sets of strong ground motion data,using the simplified attenuation relationship model based on NGA,the random effect method was used to obtain the PGA,PGV,and pseudo-acceleration response spectra(PSA)(damping ratio=5%)period from 0.01 s to 8 s.Through contrast with the attenuation relationship in other parts of Sichuan,this model can well predict the strong ground motion attenuation of Lushan aftershocks.The attenuation relationship on both the rock site and soft site is consistent in the short-term with the outcome of Lu Dawei's model.In the case of long periods,however,the outcome of this model in the soft site is larger than that of Lu Dawei’s model and is lower at rock site than that of Yu Yanxiang’s model.Therefore,when using the attenuation relationship derived from this paper,special attention should be paid to the influence of site and period.