地震研究

2009年云南姚安M_S6.0地震余震序列尾波Q_c值研究^*

李琼,秦嘉政,钱晓东,赵小艳,毛慧玲

(云南省地震局,云南昆明 650224)

关键词：姚安地震; 尾波衰减; 余震序列; 地壳Q_c值

Study on the Coda Q_c-value for Aftershock Sequence of Yao'an M_S6.0 earthquake in Yunnan in 2009

LI Qiong,QIN Jia-zheng,QIAN Xiao-dong,ZHAO Xiao-yan,MAO Hui-ling

(Earthquake Administration of Yunnan province,Kunming 650224,Yunnan,China)

Keywords：Yao'an earthquake; coda attenuation; aftershock sequence; crustul Q_c-value

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参考文献

利用云南大姚地震台记录到的2009年姚安6.0级地震余震序列的数字化波形观测资料,基于尾波单次散射理论,估算该次地震震源区尾波Q_c值。结果表明:中心频率为1.5 Hz时,振幅衰减率β(f)在-0.141 27～-0.043 05之间,平均值为-0.074 60; Q_c值在33.3～99.8之间,平均值为65.5。并得出Q_c值与频率的关系:尾波波源因子与震级成正比,与频率成反比。主震发生后头几天,尾波Q_c值(1.5 Hz)波动较大,之后在±1.5倍方差线内趋于稳定,且没有超过5级的强余震发生。姚安地区尾波Q_c值具有构造运动活跃、地震活动频繁地区的低Q_c值特征。

The coda-wave attenuation factor Q_c at the source region of Yao'an, Yunnan, M_S6.0 earthquake in 2009 is estimated through single-scattering theory of coda wave on the basis of the digital waveform data of aftershock sequence recorded by Da'yao Station. When central frequency f=1.5 Hz, the coda attenuation ratio β(f) in Yao'an region ranges from -0.141 27 to -0.043 05, and the average is -0.074 60. The Q_c-value of coda ranges from 33.3 to 99.8, and the average is 65.5.The relation between the Q_c-value and frequency f is Q_c(f)=45.3 f^0.97. The coda factor is in direct proportion to magnitude,and in inverse proportion to frequency. In the first few days after the main shock, the Q_c-value(1.5 Hz)of coda fluctuated obviously, it showed a tendency toward stabilization within the line of ±1.5 times of variance, and the strong aftershocks smaller than M5 will occur. The Yao'an region has the characteristics of active tectonic-movement, frequent seismic-activity, and low Q_c-value.

引言
1 资料
2 方法原理及数据处理
3 计算结果
4 讨论和结论

图1 用于计算的地震震中及台站分布图<br/>Fig.1 Earthquake epicenters used to calculate and the station distribution

图1 用于计算的地震震中及台站分布图
Fig.1 Earthquake epicenters used to calculate and the station distribution

图2 表1中02号地震原始波形及滤波结果图<br/>Fig.2 Original waveforms and filtering results of No.02 earthquake in Tab.1

图2 表1中02号地震原始波形及滤波结果图
Fig.2 Original waveforms and filtering results of No.02 earthquake in Tab.1

图3 各中心频率对应的t与[A(f,t)×t]的数据点及回归直线<br/>Fig.3 Data points and regression line between t and [A(f,t)×t]corresponding to different center frequency

图3 各中心频率对应的t与[A(f,t)×t]的数据点及回归直线
Fig.3 Data points and regression line between t and [A(f,t)×t]corresponding to different center frequency

表1 姚安地震余震序列尾波振幅衰减率β(f)及Qc值<br/>Tab.1 Attenuation ratio β(f)and the coda Qc values for aftershock sequences of Yao'an earthquake

表1 姚安地震余震序列尾波振幅衰减率β(f)及Qc值
Tab.1 Attenuation ratio β(f)and the coda Qc values for aftershock sequences of Yao'an earthquake

图4 尾波Qc值与频率f变化特征(粗线表示各中心频率平均值)<br/>Fig.4 Variation diagram between the coda value Qc and frequency f

图4 尾波Qc值与频率f变化特征(粗线表示各中心频率平均值)
Fig.4 Variation diagram between the coda value Qc and frequency f

图5 尾波波源因子lnA0(f)与震级ML的关系<br/>Fig.5 Relationship between the coda factor

图5 尾波波源因子lnA0(f)与震级ML的关系
Fig.5 Relationship between the coda factor

表2 姚安台估算的不同中心频率平均β(f)值和Qc值<br/>Tab.2 Average attenuation ratio β(f)and the coda Qc values of different center frequency estimated through data recorded by Yao'an station

表2 姚安台估算的不同中心频率平均β(f)值和Qc值
Tab.2 Average attenuation ratio β(f)and the coda Qc values of different center frequency estimated through data recorded by Yao'an station

图6 2009年姚安地震余震序列尾波Qc值随时间变化(上下两条虚线为1.5倍方差)<br/>Fig.6 Coda Qc values of Yao'an aftershock sequences change over time in 2009(Upper and lower dashed lines represent twice of variance)

图6 2009年姚安地震余震序列尾波Qc值随时间变化(上下两条虚线为1.5倍方差)
Fig.6 Coda Qc values of Yao'an aftershock sequences change over time in 2009(Upper and lower dashed lines represent twice of variance)

图7 不同地区尾波衰减Q-1c值随频率的变化特征(1.美国中东部地区; 2.美国西部地区; 3.日本关东地区; 4.日本大石山地区; 5.美国加州斯通峡谷地区; 6.云南武定地区; 7.美国加州帝王谷地区; 8.河北昌黎地区; 9.云南施甸地区; 10.云南姚安地区)<br/>Fig.7 Coda Q-1C value variation with frequency in different areas(1.Central and eastern United States; 2.Western UnitedStates; 3.Japan's Kanto region; 4.Japan's Ishiyamd areas; 5.Stone Canyon area,California,United States; 6.Wudingregion in Yunnan; 7.Imperial valley region,California,UnitedStates; 8.Changli area in Hebei; 9.Shidian area in Yunnan; 10.Yao'an area in Yunnan)

图7 不同地区尾波衰减Q-1c值随频率的变化特征(1.美国中东部地区; 2.美国西部地区; 3.日本关东地区; 4.日本大石山地区; 5.美国加州斯通峡谷地区; 6.云南武定地区; 7.美国加州帝王谷地区; 8.河北昌黎地区; 9.云南施甸地区; 10.云南姚安地区)
Fig.7 Coda Q-1C value variation with frequency in different areas(1.Central and eastern United States; 2.Western UnitedStates; 3.Japan's Kanto region; 4.Japan's Ishiyamd areas; 5.Stone Canyon area,California,United States; 6.Wudingregion in Yunnan; 7.Imperial valley region,California,UnitedStates; 8.Changli area in Hebei; 9.Shidian area in Yunnan; 10.Yao'an area in Yunnan)