烈度衰减关系的改进及其在地震危险性分析中的应用

IMPROVEMENT ON RELATIONSHIP OF INTENSITY ATTENUA—TION AND ITS APPLICATION IN SEISMIC RISK ANALYSIS

本文在系统地总结了前人关于地震烈度衰减关系研究的基础上,将长轴烈度衰减关系变为短轴仍采用常规形式,对长短轴分别回归,并给出了西北地区的回归结果。经过这样处理后的烈度衰减关系具有如下特征:在震中,长短轴烈度相等,在远场,长短轴烈度曲线相交,即椭圆等震线变成了圆,而且不同震级的等震线在蜕化成圆时所对应的震中距也不同。将该烈度衰减关系用于甘肃某市的地震危险性计算,并与国家地震局危险性程序所得结果相比较,产生了如下差异:中等烈度值所对应的概率增大,高烈度所对应的概率略有降低。

On the bace of the systematic study on earthquake intensity attenuation done by the predecessors, this paper changes the long axis intensity attenuation relation as I_(a)=C_(1)+C_(2)M+b C_4/)R_a^(1/3)ln(R_a+R_o)/M,the short one is still the common form.The paper regresses independently to materials of long axis intensity and the short one,and gives the results in northwest china.The improved intensity attenuation relationship has such characteristics:in the epicentres, the long axis intensity equals the short one;in the far-field,the long axis intensity attenuation curves cross the short one,i.e. elliptic isoseismal becomes a circle and epicentral distance corresponding to a circle changes with the magnitude.Using the improved relationship,the author calculates the seismic risk of a city in Gansu province,and compares its resuits with that seismic risk program of SSB calculates.The differences are:the probabilities corresponding to the medium intensity increase,the probabilities corresponding to the high intensity decrease a little.