1985年云南禄劝地震余震尾波 Q 值的某些研究
RESEARCH ON THE REGIONAL Q VALUES OF CODA WAVES FOR THE AFTERSHOCKS IN LUQUAN, YUNNAN OF 1985
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摘要: 建立在用来解释地方震和区域地震的尾波散射模型的基础上,用云南短周期区域台网12个台站的 VGK 地震仪记录的68个禄劝地震的余震序列尾波观测资料,分六个时间段估算了尾波 Q 值.发现在所观测的频率范围内(0.40——1.65Hz),Q 值与频率有关,估算的 Q 值在80——240之间,频率相关值=0.45.对表示散射强度的波源因子 B(fp)的估算结果多数在10-23——10-24量级,低 Q 值地区表现出激发强度高.值得注意的是禄劝地震前后,离震中区较近的台站所测得的 Q 值发生了明显变化,有的变化达2.0倍以上.Q 值随时间的区域变化,这在地震预报中也许有重要的实际意义.此外,测定了余震震源参数.对震源参数间的定量关系的讨论结果给出:IgE=1.59ML+11.335;E=(2.1010-5M0;在3.0ML5Pa,一个显著的特征是应力降与地震震级不存在明显的线性关系.Abstract: On the basis of a scattering model to explain the coda waves of local and regional earthquakes (K. Aki, 1969), data are obtained from over 68 aftershocks with magnitudes between 3.0 to 4.9 of the Luquan earthquake, recorded by 12 VGK short-period seismogrphs of the Seiemic Network of Yunnan Province. For six time windows are determined the coda Q values, the data cover a range of frequencies from 0.40 to 1.65 Hz. The frequency dependence of Q is observed in the range of frequencies considered. The estimated coda Q values is 80 to 240, the coefficient of frequency dependence is = 0.45. The source factor Bfp = 10-23-10-24, a measure if the intensity if scattering is obtained for 10 stations. The regions of lower Q values exhibit strong scattering. It should be noted that the aftershock coda Q is about a half of the normal value for near stations before the Luquan earthquake. This variation of Q may be taken as a significance earthquake precursor in predication of seismic trend.In addition, the aftershock source parameters are determined, and the quantitative relationships among the source parameters are discussed. For 3.0MLL + 11.335, E = (2.1010-5) Mo, a =0.40-0.80km, = (6.0-130) 105 Pa. A significant result is that there is no linear relationship between and ML.
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[1] Aki, K., Analysis of the seismic coda of local earthquakes as scattered waves, J, Geophys. Res., 74, 615——631, 1969.
[2] Singly S. and R. B. Herrmann, Regionalization of crustal coda S2 in the continental United States, J, Geophys. Res., 88, 527——538, 1983.
[3] Peishan Chen, O. W. Nuttli, Wenhua Ye and Jiazheng Qin, Estimates of short——period ,8Z values and seismie moments from coda waves for earthquakes of the Beijing and Yunnan regions of China, Bull. Seism.Sot. Amen, 74, 1189——1207, 1984.
[4] 秦嘉政、陈培善,用地震波的持续时间测定川滇地区的近震震级,地震学报,6, 58——65, 1984,
[5] 秦嘉政、阐荣举,用近震尾波估算昆明及其周围地区的Q值和地震矩,地球物理学报,29, 145——156, 1986.
[6] 林邦慧、李志勇、魏富胜,京津地区Q值及平均应力降的分布特征,地球物理学报,25, 344——351, 1982,
[7] Anshu Jin and K. Aki, Temporal Change in coda Q before .the Tangshan earthquake of 1976 and the Haicheng earthquake of 1975, J. Geophys, Res., 91, 665——673, 1986.
[8] Gao, L. S., N. N. Biswas, L. C. Lee, and K. Aki, Effects of multiple scattering on coda waves in, three——dimensional medium, PAGEOPH, 121, 3——15, 1983.
[9] Pulli, J. J., Attenuation of coda waves in New England, Bull. Seism. Sot. Amen, 74, 1149——1166,1984.
[10] 秦嘉政、李宁、胡克坚,禄劝地震余震序列尾波衰减特征,地震研究,增刊,1985.
[11] Vassilion, M. S. and H. Kanamori,地震中的能量释放,世界地震译丛,1982, 5: 42——52,
[12] 秦嘉政、阐荣举,云南地区区域剪切应力值及其对地震危险性的佑计,地震研究,9, 523——536, 1986.[1] Aki, K., Analysis of the seismic coda of local earthquakes as scattered waves, J, Geophys. Res., 74, 615——631, 1969.
[2] Singly S. and R. B. Herrmann, Regionalization of crustal coda S2 in the continental United States, J, Geophys. Res., 88, 527——538, 1983.
[3] Peishan Chen, O. W. Nuttli, Wenhua Ye and Jiazheng Qin, Estimates of short——period ,8Z values and seismie moments from coda waves for earthquakes of the Beijing and Yunnan regions of China, Bull. Seism.Sot. Amen, 74, 1189——1207, 1984.
[4] 秦嘉政、陈培善,用地震波的持续时间测定川滇地区的近震震级,地震学报,6, 58——65, 1984,
[5] 秦嘉政、阐荣举,用近震尾波估算昆明及其周围地区的Q值和地震矩,地球物理学报,29, 145——156, 1986.
[6] 林邦慧、李志勇、魏富胜,京津地区Q值及平均应力降的分布特征,地球物理学报,25, 344——351, 1982,
[7] Anshu Jin and K. Aki, Temporal Change in coda Q before .the Tangshan earthquake of 1976 and the Haicheng earthquake of 1975, J. Geophys, Res., 91, 665——673, 1986.
[8] Gao, L. S., N. N. Biswas, L. C. Lee, and K. Aki, Effects of multiple scattering on coda waves in, three——dimensional medium, PAGEOPH, 121, 3——15, 1983.
[9] Pulli, J. J., Attenuation of coda waves in New England, Bull. Seism. Sot. Amen, 74, 1149——1166,1984.
[10] 秦嘉政、李宁、胡克坚,禄劝地震余震序列尾波衰减特征,地震研究,增刊,1985.
[11] Vassilion, M. S. and H. Kanamori,地震中的能量释放,世界地震译丛,1982, 5: 42——52,
[12] 秦嘉政、阐荣举,云南地区区域剪切应力值及其对地震危险性的佑计,地震研究,9, 523——536, 1986.
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