单台Lg尾波Q_(Lg)~c的测量研究
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摘要
将单台记录叠加频谱比法（简称SSR法）应用于震中距小于500km的区域地震Lg尾波为lHz下的值，n是与频率f有关的指数）的提取之中·为了检验方法的稳定性和可靠性，我们选用两组发生在不同地区的地震记录．一组是1989-10-18大同主震（ML＝5．9）的15个余震，北京遥测地震台网记录到的信噪比较高的Lg尾波序列。另一组是秦岭造山带数字流动地震观测台网记录到的1995年甘肃平凉两次地震信噪比较高的Lg尾波序列．每一组地震的震源参数基本相同，即它们到某一特定台站的路径几乎相同，得到的 可以认为是不受震源影响的地震一台站路径上的平均衰减效应·两区域 的测量结果表明：（1）尽管两个地震观测台网所用观测仪器不同，每个台站的观测条件不同，所记录的地震也不尽相同，但对Q_0和，的拟合结果线性程度都比较高，说明SSR法是稳定的；（2）同一震群的不同地震到某一特定台站测得的结果基本一致，即Q_0值及其平均值大都在其标准差范围之内，说明SSR法是可靠的。（3）对同一地震不同方位各台站的Lg尾波测量结果可以看出，穿过不同构造区的Q_0值存在明显差异,如果这些差异可以看作是构造上横向差异的表现，那么，如果选择方位分布好的一定数量的地震，而记录台站在研究区又具有合适分布，利用这些观测得到的?
A stacked spectral ratio method is applied to the measurement of Lg coda Q at regional epicentral, distances (△＜ 500km). In order to test the stability and reliabilityof the method, we select tWo sets of high signal to noise ratio seismic records atdifferent regions. One set is Lg coda bine series from the Beijing telemetry seismicnetwork observed 15 aftershocks of the Datong principal earthquake on Oct 18, 1989(ML = 5.9). Other set is from the portable digital seismic network observed two earthquakes in Pingliang, Gansu province. The source parameters basically are sameaxnong every set of earthquakes, that is to say, their ray paths to the given stationare almost same. So obtained Q can be regarded as an average attenUation effectover the paths, which is not affected by the sources. The measuring Q results showthat: (1) Although there are different instruments used in two seismic netWorks withdifferent observation condihons in every stations, fitting resultS of the Q and ηarehighly linear. It indicates that the SSR method is stable. (2) There are the basicallysame resultS of Lg coda Q at a given station observed different earthquakes of thesame set i,e. Ω0 and their average values are almost within the range of the standarderror. It indicates that the SSR method is reliable. (3) Based on the measuring resultsof Lg Q at different stations recorded the same earthquake, it can be seen that thereis obvious difference, which can be regarded as the lateral difference of the toctonicstrucks, on Lg coda Q0 passing through different tectonic area. So if we select someearthquakes with a good azimuth distribuhon and there are a proper stahon distribution,we can image on ofs in the study area using measuring Q.
A stacked spectral ratio method is applied to the measurement of Lg coda Q at regional epicentral, distances (△＜ 500km). In order to test the stability and reliabilityof the method, we select tWo sets of high signal to noise ratio seismic records atdifferent regions. One set is Lg coda bine series from the Beijing telemetry seismicnetwork observed 15 aftershocks of the Datong principal earthquake on Oct 18, 1989(ML = 5.9). Other set is from the portable digital seismic network observed two earthquakes in Pingliang, Gansu province. The source parameters basically are sameaxnong every set of earthquakes, that is to say, their ray paths to the given stationare almost same. So obtained Q can be regarded as an average attenUation effectover the paths, which is not affected by the sources. The measuring Q results showthat: (1) Although there are different instruments used in two seismic netWorks withdifferent observation condihons in every stations, fitting resultS of the Q and ηarehighly linear. It indicates that the SSR method is stable. (2) There are the basicallysame resultS of Lg coda Q at a given station observed different earthquakes of thesame set i,e. Ω0 and their average values are almost within the range of the standarderror. It indicates that the SSR method is reliable. (3) Based on the measuring resultsof Lg Q at different stations recorded the same earthquake, it can be seen that thereis obvious difference, which can be regarded as the lateral difference of the toctonicstrucks, on Lg coda Q0 passing through different tectonic area. So if we select someearthquakes with a good azimuth distribuhon and there are a proper stahon distribution,we can image on ofs in the study area using measuring Q.
引文
1 Aki N Analysis of the seismic coda of local earthquake as scattered waves.J Geophys. Ass, 1969, 74(2):615-631
2 Hermann R B. Q eshmates using the coda of local earthquakes. Bull Seism. Soc Am、 1980, 70(2):447-468
3 Singh S K. Herrmann R B.Regionalization of crustal coda Q in the continental United States.J. Geophys.Res.3 1983, 88(B1):527-538
4 Jin A, Aki K. Spatial and temperal correlahon between coda Q and seisnucity in China.Bull. Seism Soc.Am,1988,78(2):741-769
5 Xie J, Nuttli O W Intepretation of high-frequency coda at lafge distances: stochastic modeling and method of inversion. Geophys, J, 1988, 95(2):579-595
6 Xie J, Mitchell B J. A back projection method for imaging large-scale aateral variaion of Lg coda Q with application to continental Africa, Geophys. J.Int, 1990,100(1):161-181
7 Mitchell B J.Anelastics structure and evolution of the contiental crust and upper mantle form seism Rev .of Geophysics.1995, 33(2):441-462
8 蒋耀明,葛焕称.Lg波衰减与中国大地构造特征关系初析.见:地球物理学报编辑委员会编.八十年代中国地球物理学进展.北京:学术书刊出版社,1989.307-317 JIANG Yao-Ming, GE Huan-Cheng. Relationship between Lg attenuation and geotectonic chareters in China. In: Editorial Comnnttee of Chinese Journal of Geophysics ed. Geophysics in The Eightes(in Chinese). Beijing: ACademia Book and Periodical Press, 1989, 307-317
9 张国伟,孟庆任,赖绍聪.秦岭造山带的结构构造.中国科学(B),1995,25:994-1003 ZHANG Guo-Wei, MENG Qing-Ren, LAI Shao-Cong The structure in the Qinling orogenic belt(in Chnese). deience in China(series B), 1995, 25:994-1003
10 Mayeda K M, Walter W. A new brodband magnitude based on coda envelopes (abstract) Seismal. Res.Letter, 1994, 65(1):49
2 Hermann R B. Q eshmates using the coda of local earthquakes. Bull Seism. Soc Am、 1980, 70(2):447-468
3 Singh S K. Herrmann R B.Regionalization of crustal coda Q in the continental United States.J. Geophys.Res.3 1983, 88(B1):527-538
4 Jin A, Aki K. Spatial and temperal correlahon between coda Q and seisnucity in China.Bull. Seism Soc.Am,1988,78(2):741-769
5 Xie J, Nuttli O W Intepretation of high-frequency coda at lafge distances: stochastic modeling and method of inversion. Geophys, J, 1988, 95(2):579-595
6 Xie J, Mitchell B J. A back projection method for imaging large-scale aateral variaion of Lg coda Q with application to continental Africa, Geophys. J.Int, 1990,100(1):161-181
7 Mitchell B J.Anelastics structure and evolution of the contiental crust and upper mantle form seism Rev .of Geophysics.1995, 33(2):441-462
8 蒋耀明,葛焕称.Lg波衰减与中国大地构造特征关系初析.见:地球物理学报编辑委员会编.八十年代中国地球物理学进展.北京:学术书刊出版社,1989.307-317 JIANG Yao-Ming, GE Huan-Cheng. Relationship between Lg attenuation and geotectonic chareters in China. In: Editorial Comnnttee of Chinese Journal of Geophysics ed. Geophysics in The Eightes(in Chinese). Beijing: ACademia Book and Periodical Press, 1989, 307-317
9 张国伟,孟庆任,赖绍聪.秦岭造山带的结构构造.中国科学(B),1995,25:994-1003 ZHANG Guo-Wei, MENG Qing-Ren, LAI Shao-Cong The structure in the Qinling orogenic belt(in Chnese). deience in China(series B), 1995, 25:994-1003
10 Mayeda K M, Walter W. A new brodband magnitude based on coda envelopes (abstract) Seismal. Res.Letter, 1994, 65(1):49
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