中国西部地区场地放大模型

Model of Site Amplification Factor for Western China

为探讨场地对地震动的影响，选取汶川地震主震、余震记录及美国下一代地震动衰减关系（NGA）项目的强震记录，通过比较地震动观测值与基岩衰减关系预测值得到场地放大系数．分析得出以Vs30和参考地震动为变量的场地放大连续函数模型．模型考虑了场地的K30对地震动影响的差异，反映了汶川地区场地条件对地震动的影响．通过随机效应方法回归了模型系数．模型结果表明：当参考地震动小于45～55gal时，其对场地放大无影响；当参考地震动大于45～55gal时，相同场地上随其增大场地放大系数减小；而且参考地震动对软场地上短周期地震动的场地放大影响显著，对硬土场地影响不显著．

To investigate the effect of site condition on ground motion, strong motion records of Wenchuan earth- quake and next generation attenuation （NGA） were used in this study. Site amplification factors were obtained by com- paring the spectral accelerations from recordings and rock attenuation relationship. A model for ground motion ampli- fication which is dependent on Vs30 and reference ground motion was developed. The model takes into account the influence of different Fs30 within the same site category on ground motion and reflects the site condition specialty of Wenchuan area. The coefficients were estimated using random effect method. It is shown that the site factor is inde- pendent of reference ground motion lower than 45--55 gal. The factor decreases with increasing reference motion when it is greater than 45--55 gal. The reference ground motion has an appreciable impact on low-period motion but has no influence on long-period and hard soil site.