江西九江-瑞昌震区的尾波衰减特征初探
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摘要
根据单次散射模型,利用数字地震记录资料研究和讨论了江西省九江-瑞昌震区的尾波衰减特征,获得了可信的结果。经过计算,震中距30 km内的5个地震台站得到Q0值在75~79内波动。η值大体可以分为两类:九江台和范镇台η值为0.86~0.88;丁家山、狮子洞和武皎台η值为0.94~0.97,这种差别可能与台站方位有一定的关系。考虑到此次地震的破裂尺度不会太大,可采用后3个台的计算结果,拟合得到九江-瑞昌震区尾波Qc值随频率的变化关系为Qc(f)=(77.5±15.6)f0.96±0.09。九江-瑞昌震区的Q0值为77.5,η值为0.96,与云南武定、施甸地区接近,这种类似现象是构造运动活跃地区的特征体现还是反映了中强地震破裂区局部介质性质的一种共性,有待于进一步深入研究。本研究参与计算的5个台站最大尾波流逝时间为40~44 s,得到的平均采样体深度约为53 km,相对江西地区地壳平均厚度33 km而言,结果反映的是九江-瑞昌震区地壳和上地幔顶部的介质性质。
Based on the single scatter model(Aki),value of coda was calculated in Jiujiang—Ruichang earthquake-stricken area in Jiangxi province,using digital seismic wave recorded by five stations whose epicenter distance was less than 30 km.The result shows the seismic coda attenuation feature in the relative region as follows: ① The value of varies form 70 to 79,based on value of η,the result showed two kinds of change,the η value,obtained from these wave data recorded in the Jiujiang and Fangzhen stations,varies from 0.86 to 0.88,the other value,obtained from the wave data recorded in the Dingjiashan,Shizidong and Wujiao stations,varies from 0.94 to 0.97.The deference among the value of η may correlated to the direction of stations which recorded these wave.Taking the size of the earthquake rupture into account,the mean coda attenuation coefficient in the area was obtained just using the wave data obtained from the late 3 stations,the result is Q_c(f)=(77.5±15.6)f~(0.96±0.09).② The result is in accordance with what obtained in Wuding Shidian area in Yunnan Province,the result may show that the geologic structure is identical in the two areas.In the study 40~44 s of elapsed time windows were used to calculate the attenuation coefficient,the corresponding sampling depth is about 53 km.The result shows the attenuation feature of the earth crust and the upper mantle in the(area.)
Based on the single scatter model(Aki),value of coda was calculated in Jiujiang—Ruichang earthquake-stricken area in Jiangxi province,using digital seismic wave recorded by five stations whose epicenter distance was less than 30 km.The result shows the seismic coda attenuation feature in the relative region as follows: ① The value of varies form 70 to 79,based on value of η,the result showed two kinds of change,the η value,obtained from these wave data recorded in the Jiujiang and Fangzhen stations,varies from 0.86 to 0.88,the other value,obtained from the wave data recorded in the Dingjiashan,Shizidong and Wujiao stations,varies from 0.94 to 0.97.The deference among the value of η may correlated to the direction of stations which recorded these wave.Taking the size of the earthquake rupture into account,the mean coda attenuation coefficient in the area was obtained just using the wave data obtained from the late 3 stations,the result is Q_c(f)=(77.5±15.6)f~(0.96±0.09).② The result is in accordance with what obtained in Wuding Shidian area in Yunnan Province,the result may show that the geologic structure is identical in the two areas.In the study 40~44 s of elapsed time windows were used to calculate the attenuation coefficient,the corresponding sampling depth is about 53 km.The result shows the attenuation feature of the earth crust and the upper mantle in the(area.)
引文
①朱新运等,浙江省及邻近区域尾波Q值研究,2006。
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[2]朱新运,刘杰,张帆,等.基于Aki模型的近震S波尾波Q值求解及分析软件研制[J].地震研究,2006,29(1):76-80.
[3]Pulli J.Attenuation of coda wave in New England[J].Bull Seis Soc Amer,1984,1149-1166.
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[6]Jin A,Aki K.Temporal changes in codaQbefore the Tangshan earthquake of 1976 and the Hai-cheng earthquake of 1975[J].J Geophys Res,1986,91:665-673.
[7]秦嘉政.云南地区短周期波区域Q值与地震烈度衰减[A].云贵地区地震危险性研究文集[C].昆明:云南科技出版社,1989.253-260.
[8]陈学庭.澜沧和耿马大地震Q值随时间的变化[M].北京:地震出版社,1992.
[9]秦嘉政,李白基,钱晓东,等.云南武定地震余震近场尾波衰减的区域特征[J].地震学报,2001,23(1):87-97.
[10]钱晓东,李白基,秦嘉政.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,2004,25(1):9-17.
[11]张培震,邓起东,张国民,等.中国大陆的强震活动与活动地块[J].中国科学(D辑),2003,33(增刊):12-20.
[12]崔学军,陈祥云,杨建国,等.广济-九江同步耦合断裂及其控岩、控矿作用[J].地质科技情报,2002,21(3):1-6.
[1]Aki K,Chouet B.Origin of coda waves:source,attenuation and scattering effects[J].J GeophysRes,1975,80:3322-3342.
[2]朱新运,刘杰,张帆,等.基于Aki模型的近震S波尾波Q值求解及分析软件研制[J].地震研究,2006,29(1):76-80.
[3]Pulli J.Attenuation of coda wave in New England[J].Bull Seis Soc Amer,1984,1149-1166.
[4]杨明桂,王昆.江西省地质构造及地壳演化[J].江西地质,1994,8(4):239-251.
[5]Castro R R,Luca T,Giancarlo M,et al.The spectral Decay Parameters Kin the region of Umbria-Marche,Italy[J].J Geophys Res,2000,105(B10):23811-23823.
[6]Jin A,Aki K.Temporal changes in codaQbefore the Tangshan earthquake of 1976 and the Hai-cheng earthquake of 1975[J].J Geophys Res,1986,91:665-673.
[7]秦嘉政.云南地区短周期波区域Q值与地震烈度衰减[A].云贵地区地震危险性研究文集[C].昆明:云南科技出版社,1989.253-260.
[8]陈学庭.澜沧和耿马大地震Q值随时间的变化[M].北京:地震出版社,1992.
[9]秦嘉政,李白基,钱晓东,等.云南武定地震余震近场尾波衰减的区域特征[J].地震学报,2001,23(1):87-97.
[10]钱晓东,李白基,秦嘉政.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,2004,25(1):9-17.
[11]张培震,邓起东,张国民,等.中国大陆的强震活动与活动地块[J].中国科学(D辑),2003,33(增刊):12-20.
[12]崔学军,陈祥云,杨建国,等.广济-九江同步耦合断裂及其控岩、控矿作用[J].地质科技情报,2002,21(3):1-6.
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