汶川8.0级地震前紫坪铺水库小震活动及震源参数研究
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摘要
利用区域和水库地震台网记录的数字地震波资料,研究了汶川8.0级地震前的2000年1月1日~2008年5月11日紫坪铺水库区的地震活动及震源参数。结果表明:汶川8.0级地震前该区域小震活动持续,地震活动水平为ML2~3,自2005年9月紫坪铺水库蓄水以来,特别是2008年2月地震活动明显增加,但从长期的序列来看,地震活动频次和强度仍在区域地震活动的正常起伏范围。汶川8.0级地震发生前近3个月内,中小地震的视应力差值Δσapp普遍大于0,计算得到的视应力总大于其拟合值。汶川8.0级地震震中位于低应力区,而相对较高的视应力差值分布在震中以东地区,局部出现视应力增加的现象。
Based on the digital seismic waveform data observed from regional and reservoir seismic networks,the seismicity and source parameters of Zipingpu Dam from January 1,2000 to May 11,2008 before the Wenchuan M_S8.0 earthquake is studied.The analysis results show a continuous activity of small earthquakes before Wenchuan M_S8.0 earthquake,and the level of seismic activity was from M_L2.0 to M_L3.0 in recent years.The impoundment of Zipingpu Dam started in September 2005,the obvious increment of seismic activities occurred on February 2008.But according to the analysis results of a more long time series,the frequency and intensity of seismic activities still do not exceed its range,which still belongs to a fluctuation of regional seismic activities or tectonic activity.At the same time,we also research the spatio-temporal distribution and change of apparent stress difference in source region before great earthquake,and the result shows that the apparent stress values of small earthquakes are generally higher than fitted values of apparent stress in reservoir area during near three months before the Wenchuan M_S8.0 earthquake.It can be seen from spatial distribution of apparent stress difference,the epicenter of Wenchuan M_S8.0 earthquake located at low stress distribution area,and the relatively high apparent stress difference is in the east area of epicenter.Local area presents the phenomenon of apparent stress increment.
Based on the digital seismic waveform data observed from regional and reservoir seismic networks,the seismicity and source parameters of Zipingpu Dam from January 1,2000 to May 11,2008 before the Wenchuan M_S8.0 earthquake is studied.The analysis results show a continuous activity of small earthquakes before Wenchuan M_S8.0 earthquake,and the level of seismic activity was from M_L2.0 to M_L3.0 in recent years.The impoundment of Zipingpu Dam started in September 2005,the obvious increment of seismic activities occurred on February 2008.But according to the analysis results of a more long time series,the frequency and intensity of seismic activities still do not exceed its range,which still belongs to a fluctuation of regional seismic activities or tectonic activity.At the same time,we also research the spatio-temporal distribution and change of apparent stress difference in source region before great earthquake,and the result shows that the apparent stress values of small earthquakes are generally higher than fitted values of apparent stress in reservoir area during near three months before the Wenchuan M_S8.0 earthquake.It can be seen from spatial distribution of apparent stress difference,the epicenter of Wenchuan M_S8.0 earthquake located at low stress distribution area,and the relatively high apparent stress difference is in the east area of epicenter.Local area presents the phenomenon of apparent stress increment.
引文
刘红桂、刘杰、丁页岭等,2006,地震视应力在云南地震序列中的前兆特征,地震学报,28(5),462~471。
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Brune J N,1970,Tectonic stress and spectra of seismic shear wave from Earthquake,Geophys.Res.,75(136),4997~5009.
Chael E P,1987,Spectral scaling of earthquakes in the Miramichi region of New Brunswick,Bull Seism Soc Amer,77,347~365.
Pulido N,Irikura K,2000,Estimation of dynamic rupture parameters from the radiated seismic energy and apparent stress,Geophys ResLett,27,3945~3948.
Wyss,M.and Brune,J.N.,1968,Seismic moment,stress,and source dimensions for earthquakes in the California-Nevada region,J.Geophys.Res.,73,4681~4694.
Wyss M.,1970a,Stress estimates for South American shallow and deep earthquakes,J.Geophys.Res,75(8),1529~l544.
Wyss M.,1970b,Apparent stresses of earthquakes on ridges compared to apparent stresses of earthquakes in trenches,Geophys.J.R.astr.Soc,19,479~484.
Zhang Zhi-wei,Cheng Wan-zheng,Ruan Xiang,et al,2009,The seismicity and tectonic stress field characteristics of the Longmenshanfault zone before WenchuanMS8.0 earthquake,Earthquake Sci,22,119~128.
秦嘉政、钱晓东,2006,云南地区地震视应力的时间和空间分布研究,地震学报,28(3),221~229。
钟羽云、朱新运、张震峰,2004,温州珊溪水库ML3.9震群震源参数特征,地震,24(3),107~114。
Brune J N,1970,Tectonic stress and spectra of seismic shear wave from Earthquake,Geophys.Res.,75(136),4997~5009.
Chael E P,1987,Spectral scaling of earthquakes in the Miramichi region of New Brunswick,Bull Seism Soc Amer,77,347~365.
Pulido N,Irikura K,2000,Estimation of dynamic rupture parameters from the radiated seismic energy and apparent stress,Geophys ResLett,27,3945~3948.
Wyss,M.and Brune,J.N.,1968,Seismic moment,stress,and source dimensions for earthquakes in the California-Nevada region,J.Geophys.Res.,73,4681~4694.
Wyss M.,1970a,Stress estimates for South American shallow and deep earthquakes,J.Geophys.Res,75(8),1529~l544.
Wyss M.,1970b,Apparent stresses of earthquakes on ridges compared to apparent stresses of earthquakes in trenches,Geophys.J.R.astr.Soc,19,479~484.
Zhang Zhi-wei,Cheng Wan-zheng,Ruan Xiang,et al,2009,The seismicity and tectonic stress field characteristics of the Longmenshanfault zone before WenchuanMS8.0 earthquake,Earthquake Sci,22,119~128.
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