2001年施甸震群非弹性衰减及震源参数特征研究
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摘要
本文根据昆明区域数字台网记录的数字地震波形资料,采用Atkinson方法反演了施甸地震震源区非弹性衰减,运用Moya方法反演了施甸震中200km区域内6个数字地震台的场地响应。首先扣除了地震记录数据中传播路径、场地响应和仪器响应的影响,继而利用遗传算法测定了2001年施甸震群的震源参数。结果表明:①地震矩和近震震级有很好的线性关系,地震矩范围为1×1012~1014N.m,震源破裂半径为157~973m,地震矩与震源半径之间亦呈线性关系。②拐角频率随地震矩的增大而减小。用最小二乘法拟合出拐角频率与地震矩之间的关系式,据此关系式可计算出拐角频率的估计值。拐角频率与其估计值之差的时间进程曲线表明,强余震发生之前会连续出现拐角频率与其估计值的差值呈高值或低值异常。③地震应力降范围为0.07~1.55MPa,应力降与近震震级无明显的依赖关系,强余震发生之前会出现高应力降异常。④余震的震源深度主要分布在5~10km,表明地震能量释放主要集中在这一深度范围内。
Based on horizontal-component digital seismograms recorded on 6 stations of the Kunming Regional Digital Network,we inverse the Non-elasticity attenuation in source region of the Shidian earthquakes using the Atkinson method and site responses of 6 stations 200km around the Shidian epicenter using the Moya method.The observational seismic waveform data are corrected by removing the propagation,instrument and site effects before the source parameters of the Shidian swarm in 2001 are obtained by using genetic algorithms.The results are as follows:(1) there is a linear relation between seismic moment and local magnitude.The seismic moment is between 1×10~(12) and 10~(14) N·m.The rupture radius of seismic focus varies from 157m to 973m.The seismic moment and the rupture radius remain a linear correlation.(2) The corner frequency increases while the seismic moment decreasing.Based on the expression between corner frequency and seismic moment by using least squares fitting,we can obtain the estimated value of corner frequency.The time-varying value of the difference between the calculated corner frequency and estimated corner frequency shows that there are continuous anomalies of high or low before strong aftershocks.(3) The seismic stress drop is in range of 0.07～1.55MPa.The stress drop seems independent of the local magnitude.The change of stress drops has feature of high value before occurrence of the strong aftershocks.(4) The depth of aftershocks is mostly in range from 5km to 10km,which means that energy release of aftershocks is mainly concentrated in this range of depth.
Based on horizontal-component digital seismograms recorded on 6 stations of the Kunming Regional Digital Network,we inverse the Non-elasticity attenuation in source region of the Shidian earthquakes using the Atkinson method and site responses of 6 stations 200km around the Shidian epicenter using the Moya method.The observational seismic waveform data are corrected by removing the propagation,instrument and site effects before the source parameters of the Shidian swarm in 2001 are obtained by using genetic algorithms.The results are as follows:(1) there is a linear relation between seismic moment and local magnitude.The seismic moment is between 1×10~(12) and 10~(14) N·m.The rupture radius of seismic focus varies from 157m to 973m.The seismic moment and the rupture radius remain a linear correlation.(2) The corner frequency increases while the seismic moment decreasing.Based on the expression between corner frequency and seismic moment by using least squares fitting,we can obtain the estimated value of corner frequency.The time-varying value of the difference between the calculated corner frequency and estimated corner frequency shows that there are continuous anomalies of high or low before strong aftershocks.(3) The seismic stress drop is in range of 0.07～1.55MPa.The stress drop seems independent of the local magnitude.The change of stress drops has feature of high value before occurrence of the strong aftershocks.(4) The depth of aftershocks is mostly in range from 5km to 10km,which means that energy release of aftershocks is mainly concentrated in this range of depth.
引文
黄玉龙、郑斯华、刘杰等,2003,广东地区地震动衰减和场地响应的研究,地球物理学报,46(1):54~61。
李立平,1990,澜沧-耿马地震震源动力学参数研究.地震研究,13(3):223~232。
李一正,1985,滇西地区震级与地震矩标度,地震研究,8(6):617~632。
刘杰、郑斯华、黄玉龙等,2003,利用遗传算法反演非弹性衰减系数、震源参数和场地响应.地震学报,25(2):211~218。
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,地震地磁观测与研究,25(1):9~17。
秦嘉政,1986,用近震尾波估算昆明及周围地区的Q值和地震矩,地球物理学报,29(2):145~156。
章文波、谢礼立、郭明珠,2001,利用强震记录分析场地的地震反应,地震学报,23(6):604~614。
叶建庆、苏有锦、刘学军等,2002,2001年云南中强地震序列震源参数,地震研究,25(2):115~123。
Abercrombie R.E.,1995,Earthquake source scaling relationships from-1 to 5MLusing seismograms recorded at 2.5km depth,J.G.R.,100:24015~24036.
Atkinson G.M.and Boore D.,1995,New ground motion relations for eastern North America,Bull.Seism Soc Am.,85:17~30.
Atkinson G.M.and Mereu R.F.,1992,The shape of ground motion attenuation curves in southeastern Canada,Bull.Seism.Soc.Am.,82:2014~2031.
Bakun W.H..1984,Seismic moments,local magnitudes,and coda-duration magnitudes for earthquakes in central California.BullSeism Soc.Am,74:439~458.
Brune J.N.,1970,Tectonic stress and the spectra of seismic shear waves from earthquake,J.G.R.,75(26):4997~5009.
Brune J.N.,1971,Correction,J G R,76(20):5002.
Chael E.,1987,Spectral scaling of earthquakes in the Miramichi region of New Brunswick,Bull Seism.Soc.Am.,77(2):347~365.
Jin Anshu,Moya C.A.and Ando M.,2000,Simultaneous determination on site response and source parameters of small earthquakesalong the Atotsugawa fault zone,Central Japan,Bull.Seism.Soc.Am.,90(6):1430~1445.
Mayeda K.and Walter W.R.,1996,Moment,energy,stress drop,and source spectra of western United States earthquakes fromregional coda evolopes,J.G.R.,101:11195~11208.
Moya C.A.,Aguirre J.and Irikura K.,2000,Inversion of source parameters and site effects from strong ground motion records usinggenetic algorithms,Bull.Seism.Soc.Am.,90(4):977~992.
Shi Jinhua,Kim W.Y.and Richards P.G.,1998,The corner frequencies and stress drops of intraplate earthquakes in the NortheasternUnited States,Bull.Seism.Soc.Am.,88:531~542.
①苏有锦、刘杰、郑斯华等,2006,云南地区S波非弹性衰减Q值研究,地震学报,待刊。
李立平,1990,澜沧-耿马地震震源动力学参数研究.地震研究,13(3):223~232。
李一正,1985,滇西地区震级与地震矩标度,地震研究,8(6):617~632。
刘杰、郑斯华、黄玉龙等,2003,利用遗传算法反演非弹性衰减系数、震源参数和场地响应.地震学报,25(2):211~218。
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,地震地磁观测与研究,25(1):9~17。
秦嘉政,1986,用近震尾波估算昆明及周围地区的Q值和地震矩,地球物理学报,29(2):145~156。
章文波、谢礼立、郭明珠,2001,利用强震记录分析场地的地震反应,地震学报,23(6):604~614。
叶建庆、苏有锦、刘学军等,2002,2001年云南中强地震序列震源参数,地震研究,25(2):115~123。
Abercrombie R.E.,1995,Earthquake source scaling relationships from-1 to 5MLusing seismograms recorded at 2.5km depth,J.G.R.,100:24015~24036.
Atkinson G.M.and Boore D.,1995,New ground motion relations for eastern North America,Bull.Seism Soc Am.,85:17~30.
Atkinson G.M.and Mereu R.F.,1992,The shape of ground motion attenuation curves in southeastern Canada,Bull.Seism.Soc.Am.,82:2014~2031.
Bakun W.H..1984,Seismic moments,local magnitudes,and coda-duration magnitudes for earthquakes in central California.BullSeism Soc.Am,74:439~458.
Brune J.N.,1970,Tectonic stress and the spectra of seismic shear waves from earthquake,J.G.R.,75(26):4997~5009.
Brune J.N.,1971,Correction,J G R,76(20):5002.
Chael E.,1987,Spectral scaling of earthquakes in the Miramichi region of New Brunswick,Bull Seism.Soc.Am.,77(2):347~365.
Jin Anshu,Moya C.A.and Ando M.,2000,Simultaneous determination on site response and source parameters of small earthquakesalong the Atotsugawa fault zone,Central Japan,Bull.Seism.Soc.Am.,90(6):1430~1445.
Mayeda K.and Walter W.R.,1996,Moment,energy,stress drop,and source spectra of western United States earthquakes fromregional coda evolopes,J.G.R.,101:11195~11208.
Moya C.A.,Aguirre J.and Irikura K.,2000,Inversion of source parameters and site effects from strong ground motion records usinggenetic algorithms,Bull.Seism.Soc.Am.,90(4):977~992.
Shi Jinhua,Kim W.Y.and Richards P.G.,1998,The corner frequencies and stress drops of intraplate earthquakes in the NortheasternUnited States,Bull.Seism.Soc.Am.,88:531~542.
①苏有锦、刘杰、郑斯华等,2006,云南地区S波非弹性衰减Q值研究,地震学报,待刊。
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