利用地方震尾波估测新丰江库区的Q值
Q-VALUE IN XINFENGJIANG RESERVOIR REGION ESTIMATED BY Q OF CODA WAVES OF LOCAL EARTHQUAKES
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摘要: 本文根据AKi单次逆向散射的尾波理论,应用Herrmann等人推广了的尾波理论模式,并假设Q与频率相关,计算了58-1,63-B和DSL-1三种短周期地震仪的尾波优势频率、尾波形状和尾波斜率作为t*函数的理论曲线,并利用库区四个台58-1仪器记录的新丰江库区的地震资料,用S-t*和C-t*两种方法,估算了新丰江水库区频率约为1.0Hz短周期波的地壳Q0值,得到Q0值在170——300之间,平均为23038;频率相关系数为0.0——0.2。Q0的平面分布表明,近坝峡谷区具有最低的Q0值。与其他地区对比后认为,库区属于地质构造相对稳定的地区。 文中还对尾波Q值的估测方法等若干问题进行了讨论。Abstract: Based on Aki's theory on single backscattering coda wave in applying the coda theory model developed by Herrmann et al. while assuming that the Q is interrelated with the frequency, theoretic curves are calculated in the paper, taking the predominant coda frequency fp(t*, ), the coda slope C(fp, t*, ) and the shape S(p, t*, ) as function of t* for the model 58-1, 63-Band DSL-1 short-period seismographs used in the Xinfengjiang region-data were obtainedfrom 55 local earthquakes, with magnitudes mostly between 3.0 and 5.0. By applying both methods of S-t* and C-t* on the seismic data reco ded with model 58-1 seismographs at four seismic stations in the Xinfengjiang region, the Qo-value of the earth's crust at a frequency around 1.0 HZ in the reservoir region is calculated as between 170 and 300, averaging 23038, and the frequency correlation coefficient being 0.0 to 0.2. Spatial distribution of Q0 indicates that the lowest Q0-value falls on the deep canyon area near the dam. Compared with data obtained in other areas, it is considered that the reservoir region is a relatively stable geologic structure.In addition, the methods of estimating the Q-value of coda waves as well as other issues concerned are also discussed in the paper.
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[11] 秦嘉政、网荣举、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,1986,29,145一155.
[12] 王妙月、杨愚源、胡毓良、李自强、陈运泰、金严、冯锐,新丰江水库地震的震源机制及其成因的初步探讨,中国科学,1976,1,55——97,
[13] 周克森,用介质一仪器脉冲响应求新丰江库区Q值,地震研究,1984,7,399——410,
[14] Anshu Jin and K. Aki, Temporal change in coda Q before the Tangshan earthnuake of 1976 and the Haicheng ear:hduake of 1975, J. Geoplzys. Pes., 1986, 91, 665——673.[1] Aki, K., Analysis of the seismic coda earthquakes as scattered waves, J. Geophys, Res., 1969, 74, 615——631.
[2] Aki, K. and B. Chovet, Origin of coda waves: source, attenuation and scattering effects, J. Geophys. Res.,1975, 80, 3322——3342.
[3] Herrmann, R. B., Q estimates using the coda of local earthquakes, Bufl. Seism. Soc, Amer., 1980, 70,447——468.
[4] Singly S. and R, B. Herrmann, Regionalization of crustal coda Q in the continental Unified States, J Geophys. Res., 1983, 88, 527——538.
[5] Chen, P. S., O. W, Nuttli, W. H. Ye and J. Z. Qin, Estimates of short——period Qvalues and seismic momenu from coda waves for earthquakes of the Beijing and Yunnan regions of China, Bull. Scisnz. Soc.mcr., 1984, 74, 1189——1207.
[6] Rautian, T. G. and V. I. Khalturin, The use of the coda for determination of the earthquake source spectrum, Bull. Seisnz. Soc. Amen, 1978, 68, 923——948,
[7] Нерсесов, И. Л., Экслериментальные Исследования сейсмической коды, Наука, 1981,издагелъство.
[8] 程德利,张裕中,尾波观测与Q值分布.地震学报,1985,7,398——407,
[9] 周克森,DSL一型流动地震仪的动态特性研究,西北地震学报,1984,6,80——89,
[10] 周克森,熏烟记录地震仪的动态分析,华南地震.1984, 4, 7——15.
[11] 秦嘉政、网荣举、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,1986,29,145一155.
[12] 王妙月、杨愚源、胡毓良、李自强、陈运泰、金严、冯锐,新丰江水库地震的震源机制及其成因的初步探讨,中国科学,1976,1,55——97,
[13] 周克森,用介质一仪器脉冲响应求新丰江库区Q值,地震研究,1984,7,399——410,
[14] Anshu Jin and K. Aki, Temporal change in coda Q before the Tangshan earthnuake of 1976 and the Haicheng ear:hduake of 1975, J. Geoplzys. Pes., 1986, 91, 665——673.
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