利用华北地区地震监测台网小震记录建立强地震动衰减关系

Strongground motion attenuation relationship for North China from small earthquake records by earthquake monitoring networks

利用华北地区宽频带数字地震监测台网小震数据,反演得到表达区域震源和地壳介质特性的六个参数,包括应力降Δσ=92 bars、品质因子Q0=241和η=0.81、几何衰减分段点R1=69 km和R2=122 km、κ0=0.061 3 s。由此计算的加速度傅里叶幅值谱,配上一个随机相位谱,合成地震动加速度时程,建立区域强地震动衰减关系。与强震数据相比,本文得到的5级和7级的曲线能够从数据中穿过,尤其是远场部分,6级的结果偏高;与经验性衰减关系比较,由于本文使用的是点源模型,与等效半径对应的曲线接近。

Six regional parameters,which describe the characteristics of regional source and crustal medium,are inversed from small earthquake data,recorded by the broadband digital earthquake monitoring network in North China. Inversed results are Δσ = 92 bars,Q0= 241,η = 0. 81,R1= 69 km,R2= 122 km and κ0= 0. 061 3 s. Acceleration Fourier amplitude spectra can be calculated by these values. Complex spectra are formed by combining with random phase spectra. Acceleration time histories can be simulated,and regional strong ground motion attenuation relationships can be established. Compared with strong ground motion data,the curves,in the cases of Mw= 5. 0 and Mw= 7. 0,pass through the data,especially on the far field,and in the case of Mw= 6. 0,the curve is higher. Compared with regional empirical attenuation relationships,the results are close to the equivalent-radius curves,since the point source model is adopted in this paper.