利用天然地震研究蒙城地震台区域范围内介质的品质因子Q值

基于单次散射模型的尾波功率谱分析法,利用安徽省蒙城区域数字地震台1999年12月30日记录震中距35 km,M_S 4.1地震波形资料计算蒙城地震台周边半径约55 km范围内区域地球介质不同频率的Q值,发现0.5—20 Hz频率范围内,Q值随频率的变化关系近似服从幂函数关系Q_c=Q_0f~η,Q_0为1 Hz时的Q值,即Q_c=27.04f~(0.9952±0.0004),其中Q值在13—533范围内,平均值为273,η值在0.9952±0.004。结果表明,蒙城地震台附近范围内Q值具有较强的频域依赖性,与他人研究求得的Q作比较,平均值结果接近该Q值可以较好反映当地地球介质的品质因子;给出当地地震波传播介质的平均自由程为15 km,探讨介质的品质因子Q(Q_c)值的物理意义及应用,对研究本地区的地震活动习性及震后趋势预测具有重要意义。

Study on the quality factor Q in Mengcheng Seismic Station area with natural earthquake data

Based on the single-scattering model of coda power spectrum analysis, using the digital waveform data of Ms 4.1 earthquake on December 30, 1999 with epicenter distance of 35 km, recorded by Mengcheng Seismic Station, Anhui Province, the media Q values at different fre- quencies are calculated for the region surrounding the station about 55 km radius. It is found that, in 0.5--20 Hz frequency range, the variation of value obeys the power function as Q= Q0fη, where Q0 is the value of Q at 1 Hz. It can be also write as Q=27.04 f^0.9952±0.0004, in which the value in the 13--533 range with the average of 267, η values is between 0. 9952±0. 004. The results showed that within the vicinity of Mengcheng sets the Q value is strongly dependent on the frequency. Comparing with the Q value calculated by other methods, The mean of this results is similar. The local Q-value obtained with this method can be a better response to the local earth medium quality factor. The mean free path of local seismic wave propagation medium is given as 15 kin. The physical meaning and applied signification in seismicity study and aftershock tendency prediction of media quality factor Q（Qc） value are discussed.