中文摘要：

高频衰减参数kappa是近场强地震动模拟中的一个重要参数，本文利用汶川地震的强震记录计算了主余震的kappa值，并分别给出了3种场地类别的kappa值随震中距和震级变化的统计参数。统计结果表明，水平方向地震动的高频衰减较明显；当震中距或震级较小时，部分强震记录的衰减缓慢；3种场地类别的kappa值统计结果均与震级和震中距有关，并随着场地类别的增大，相关系数相应增加。计算得到的kappa值离散性很大，本文在线性拟合的基础上给出了kappa的取值范围，这一范围基本控制在拟合直线两倍标准差之间。本文的研究结果对kappa值的估计有重要参考价值。

英文摘要：

The high frequency decay parameter kappa is an important parameter of near-fault strong ground motions simulation. The values of kappa for the mainshoek and aftershocks are calculated with the strong ground motions in Wenchuan earthquake. The statistical parameters are also given for three kinds of site category, which differ by epi- central distance and earthquake magnitude. The statistical results show that the high frequency decay is obvious in the horizontal ground motions. When the epicentral distance is short or the earthquake magnitude is small, the strong ground motions may decay slowly. The kappa of three kinds of site category are all related to epicentral distance and earthquake magnitude. The correlation coefficents increase with the growth of the site category. The dispersion of kappa is obvious. The range of kappa is given on the base of the linear fitting of kappa. This range is controlled un- der twice variance of the fitting line. The research results can be used to estimate the value of kappa.