澜沧江流域水电工程地区的尾波衰减
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摘要
利用围绕澜沧江水利水电枢纽工程地区的8个地震台记录到的数字化波形资料,根据尾波散射理论,以不同的中心频率研究了该地区的尾波衰减。结果显示研究区尾波的Q0值在46~80之间,平均值为63;η值在0·66~0·94之间,平均值为0·79。与云南其它地区相比,研究区的Q0值比构造活动强烈地区的要高,属于中等构造活动地区;与世界上其它地区相比,研究区的尾波衰减不同于构造地震活动相对较弱的地区,而与构造地震活动频繁、强烈的地区较为接近,因此判断澜沧江流域及周边地区未来有发生中强地震的可能。另外,地震波衰减与断层的破碎程度有明显的依赖关系,地震波经过断层破碎带时,被强烈散射和吸收,Q0值明显降低,而且,不但近场的地震波衰减具有这种性质,远场的地震波衰减也同样具有这种特性。
Using the digital waveform data recorded by 8 earthquake stations around the key hydropower control project area of the Lancang River valley, we studied coda attenuation in this area and vicinity with different center frequencies on the basis of coda scattering theory. The result shows that in studied area the Q_0 values of coda change between 46 and 80, the average is 63; η ranges from 0.66 to 0.94, the average is 0.79. Compared with other areas of Yunnan with strong tectonic seismic activity, the Q_0 values are higher in this area; compared with other areas of the world, the coda attenuation in this area is different from that in the areas with relatively weak tectonic seismic activity but close to that in ones with frequent and strong tectonic seismic activity. So we think this area is a moderate tectonic activity area and it is possible to occur moderate earthquakes in future. In addition, the attenuation of seismic waves is obviously depended on the degree of fault crushing. When seismic waves pass through the fault crushed zones, they will be intensively scattered and absorbed, therefore, Q_0 values will reduce evidently, and this character not only appears in near field but also in far field.
Using the digital waveform data recorded by 8 earthquake stations around the key hydropower control project area of the Lancang River valley, we studied coda attenuation in this area and vicinity with different center frequencies on the basis of coda scattering theory. The result shows that in studied area the Q_0 values of coda change between 46 and 80, the average is 63; η ranges from 0.66 to 0.94, the average is 0.79. Compared with other areas of Yunnan with strong tectonic seismic activity, the Q_0 values are higher in this area; compared with other areas of the world, the coda attenuation in this area is different from that in the areas with relatively weak tectonic seismic activity but close to that in ones with frequent and strong tectonic seismic activity. So we think this area is a moderate tectonic activity area and it is possible to occur moderate earthquakes in future. In addition, the attenuation of seismic waves is obviously depended on the degree of fault crushing. When seismic waves pass through the fault crushed zones, they will be intensively scattered and absorbed, therefore, Q_0 values will reduce evidently, and this character not only appears in near field but also in far field.
引文
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WoodgoldCDR.1990.EstimationofQineasternCanadausingcodawaves[J].BSSA,80:411-429.
李白基,秦嘉政,钱晓东,等.2004.云南姚安地区的尾波衰减[J].地震学报,26(1):47-52.
钱晓东,李白基,秦嘉政.2004.2001年云南施甸MS5·9地震余震序列尾波Qc值研究[J]·地震地磁观测与研究,25(1):9-17.
秦嘉政,李白基,钱晓东,等.2001.云南武定地震余震近场尾波衰减的区域特征[J].地震学报,23(1):87-97.
张天中,高龙生,张卫平.1990.滇西实验场区的Q值及其随时间窗的变化[J].地震学报,12(1):12-21.
AkiK,ChouetB.1975.Originofcodawaves:source,attenuationandscatteringeffects[J].JGR,80:3322-3342.
HartzellS,LeedsA,FrankelA,etal.1996.SiteResponseforurbanLosAngelesusingaftershocksoftheNorthridgeearthquake[J].BSSA,86(1B):168-172.
SingS,HerrmannRB.1983.RegionalizationofcrustalcodaQinthecontinentalUnitedStates[J].JGR,88:527-538.
WoodgoldCDR.1990.EstimationofQineasternCanadausingcodawaves[J].BSSA,80:411-429.
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