华北中北部地区震源参数和场地响应的联合反演

The Joint Inversion of Source Parameters and Site Effects in Central and Northern Area of North China

利用遗传算法反演华北中北部地区 2 7个地震震源谱的低频水平、拐角频率和 2 5个台站的场地响应。具体方法是利用研究区的平均衰减模型对记录谱进行路径校正 ,然后假定每一个地震的ω2 模型 ,调整低频水平和拐角频率使所有台站场地响应的标准偏差最小 ,最后给出参与计算的每个台站的场地响应。结果表明 ,17个基岩台中 11个台的场地响应在 1～ 2 0Hz范围内接近 1,6个基岩台的场地响应部分频段放大或缩小 3倍以上。8个井下摆台站的场地响应形态相同 ,表现为低频放大 ,高频部分迅速衰减。地震矩与震级的关系为logM0 =17 1+1 13ML,地震矩与震源半径的关系为logM0 =19 4 + 0 0 0 5 2r。

The low-frequency flat levels and corner frequencies of 27 earthquakes in central and northern area of North China, together with the site effects of the 25 recording stations, are inverted by using genetic algorithms. All recording spectra were corrected by averaged attenuation model of propagation-path, and for each earthquake, a different omega-squared model was assumed such that the low-frequency flat levels and corner frequencies would minimize the standard deviation of the site effects at all stations. Finally, the site effect of each station was obtained. It was observed that the site effects of 11 of 17 rock stations were approximately 1 at a range between 1Hz and 20Hz, others showed amplification or minification over three times at some frequencies. The shapes of site effects of 8 Huangtu layer stations, whose seismometers were in the wells, were similar. Their site effects showed amplification at low frequencies and minification at high frequencies. The relationship between seismic moment and magnitude is logM 0=17.1+1.13M L. The relationship between seismic moment and source radius is logM 0=19.4+0.0052r.