滇西试验场区的Q值及其随时间窗的变化
THE Q-FACTOR AND ITS TIME WINDOW DEPENDENCE IN THE AREA OF WESTERN-YUNNAN SEISMOLOGICAL EXPERIMENT SITE
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摘要: 本文试用数字地震记录求取尾波Q值及其与频率的关系.在微机上处理触发数字地震仪记录的资料,原始记录经数字滤波器作窄带通滤波得到一组分频记录,经过时间序列分析的方法,可得到能量密度随时间衰减的曲线,该曲线比从可见记录求得的较为可靠.以散射模型的理论表达式进行曲线拟合,求得Q值及其与频率的关系.值得注意的是,这个结果对某一台站并非常数,尾波Q值是时间窗(即研究所用尾波的整个延续时间)的函数,其原因可能是由于不同到时的尾波采样区域和深度不同,以及多次散射的影响等.因此,当把Q值作为地震预报的一个参数时,延续时间是一个重要的可选择的因子.Abstract: This study is an experiment of using digital seismic records to find the coda Q and its dependence on freqency. Data are recorded by triggered digital seismometers,and then are put into a microcomputer. After narrow band-pass filtering of the digital records,the digital seismograms become a set of pseudo-single frequency records. With the approach of time series analysis,decay curves of energy density against time are plotted. These curves are more reliable than those from visual seismograms. Fitting these decay curves to theoretical expression of a scattering model,the coda Q and its dependence on freqency are obtained. It can be noticed that these results are not constant for a certain station. The coda Q obtained is a function of time window which is the whole duration time of the coda used for study. The reason of this relation may be due to the difference in sampling area and depth for different arrival time of codas and the effect of multiple scattering. Therefore,when considering the coda Q as an earthquake prediction parameter,the duration time is an important factor to make choice.
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[1] Aki, K., 1969. Analysis of seismic coda of local earthquakes as scattered waves. J. Geophys. Res., 74,615——631.
[2] Aki, K,Chouet, B,19i5, Drtgin of coda waves, souruc, attenuation and scattering effects. J. Ccophys.Res., 80, 3322——3342.
[3] Sato, H, 1977. Enelrgy propagation includingt scattering effects single isotropic scattering approxima——tion. J. Phys. Esrth, 25, 27——41.
[4] Sato, H., 1978. Mean free path of S——wave under the Kanto district of Japan. J. Phys. Earth, 26, 185——198.
[5] M.巴特著,郑治真等译,1978.地球物理学中的谱分析,26——30,48——55,地震出版社.
[6] C.福里斯,A. B.季莫列娃著,粱宝洪译,1979.普通物理学(修订本),第一卷,459——466,人民教育出版社.
[7] 高龙生、石汝斌、华正兴、李瑞渲,1986.唐山一北京地区口因子随频率的变化,地震学报,8, 354——366,
[8] Gao, L. S., Hua, Z. X. and Li, R. X., 1985. Estimation of mean free path of S——waves under Beijing area by means of both intensity. and decay of coda. Gcophy. Researrh, 1, 69——83.
[9] 程德利、张裕中,1985尾波观察与Q值分布.地震学报,7,398——407,
[10] 秦嘉政、李宁、胡克坚,1987, 198,年云南禄劝地震余震尾波Q值的某些研究.地震学报,9,239 ——252,
[11] Gao, L. S,Biswas, N. N., Lee, L. C. and Aki, K., 1983. Effects of multiple scattering on coda waves in three——dimensional medium. Pageoph, 121, 3——15.[1] Aki, K., 1969. Analysis of seismic coda of local earthquakes as scattered waves. J. Geophys. Res., 74,615——631.
[2] Aki, K,Chouet, B,19i5, Drtgin of coda waves, souruc, attenuation and scattering effects. J. Ccophys.Res., 80, 3322——3342.
[3] Sato, H, 1977. Enelrgy propagation includingt scattering effects single isotropic scattering approxima——tion. J. Phys. Esrth, 25, 27——41.
[4] Sato, H., 1978. Mean free path of S——wave under the Kanto district of Japan. J. Phys. Earth, 26, 185——198.
[5] M.巴特著,郑治真等译,1978.地球物理学中的谱分析,26——30,48——55,地震出版社.
[6] C.福里斯,A. B.季莫列娃著,粱宝洪译,1979.普通物理学(修订本),第一卷,459——466,人民教育出版社.
[7] 高龙生、石汝斌、华正兴、李瑞渲,1986.唐山一北京地区口因子随频率的变化,地震学报,8, 354——366,
[8] Gao, L. S., Hua, Z. X. and Li, R. X., 1985. Estimation of mean free path of S——waves under Beijing area by means of both intensity. and decay of coda. Gcophy. Researrh, 1, 69——83.
[9] 程德利、张裕中,1985尾波观察与Q值分布.地震学报,7,398——407,
[10] 秦嘉政、李宁、胡克坚,1987, 198,年云南禄劝地震余震尾波Q值的某些研究.地震学报,9,239 ——252,
[11] Gao, L. S,Biswas, N. N., Lee, L. C. and Aki, K., 1983. Effects of multiple scattering on coda waves in three——dimensional medium. Pageoph, 121, 3——15.
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