判别小震群序列类型的新方法研究——谱振幅相关分析法
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摘要
已有研究表明,与一般性小震群相比,前震序列的震源机制更趋于一致.鉴于小地震的震源机制不易求解,本文利用谱振幅相关分析法研究小地震震源机制是否相似的问题,以探讨小震群序列类型判定的可能性.选择小震群活动频繁的云南西北部作为研究区域,计算发生在该地区的五个震群的谱振幅相关系数.结果显示,2001年施甸MS5.9级及2001年永胜MS6.0级强震震前的小震群序列谱振幅相关系数平均值分别为0.88、0.93;2002年漾濞、2003年洱源、2005年宾川三个一般性小震群的谱振幅相关系数平均值分别为0.48、0.68和0.63.表明,强震前的小震群序列与一般性小震群序列相比,谱振幅相关系数明显较大,接近于1.0,说明其震源机制相似性更为显著.本文针对小震群类型判定所作的理论推测与所研究震例实测结果基本相符合,初步表明,谱振幅相关分析法可能是判定小震群类型的物理意义较为明确的方法,具有实用价值,值得进一步深入研究.
Study shows that the focal mechanisms of foreshock sequence are more consistent than those of general small earthquake swarm.Due to the intricacy of calculating the focal mechanism of small earthquakes,we use correlation coefficient of spectral amplitude to study the consistency of focal mechanism of small earthquakes,so as to analyze the possibility of determining the type of small earthquake swarm.We apply the method to five earthquake swarms in the northwest of Yunnan Province where small earthquake occurs frequently.The results show that the mean correlation coefficient of spectral amplitude of foreshocks of the Shidian MS5.9 earthquake in 2001 is 0.88,the Yongsheng MS6.0 earthquake in 2001 is 0.93,while the general small earthquake swarms in Yangbi(2002),Eryuan(2003),Binchuan(2005) is 0.48,0.68,and 0.63 respectively.The results suggest that the correlation coefficient of spectral amplitude of foreshock sequence is larger,closer to 1.0 than that of general small earthquake swarm,which leads to more similarity of focal mechanisms of foreshock sequence.In this paper,the theoretical expectations conform to the actual calculated results in these earthquake cases.This feature preliminarily implies that the correlation analysis of spectral amplitude could serve as a method that has clear physical significance and practical utility in determining the type of the earthquake swarm,and thus be worthy of further study.
Study shows that the focal mechanisms of foreshock sequence are more consistent than those of general small earthquake swarm.Due to the intricacy of calculating the focal mechanism of small earthquakes,we use correlation coefficient of spectral amplitude to study the consistency of focal mechanism of small earthquakes,so as to analyze the possibility of determining the type of small earthquake swarm.We apply the method to five earthquake swarms in the northwest of Yunnan Province where small earthquake occurs frequently.The results show that the mean correlation coefficient of spectral amplitude of foreshocks of the Shidian MS5.9 earthquake in 2001 is 0.88,the Yongsheng MS6.0 earthquake in 2001 is 0.93,while the general small earthquake swarms in Yangbi(2002),Eryuan(2003),Binchuan(2005) is 0.48,0.68,and 0.63 respectively.The results suggest that the correlation coefficient of spectral amplitude of foreshock sequence is larger,closer to 1.0 than that of general small earthquake swarm,which leads to more similarity of focal mechanisms of foreshock sequence.In this paper,the theoretical expectations conform to the actual calculated results in these earthquake cases.This feature preliminarily implies that the correlation analysis of spectral amplitude could serve as a method that has clear physical significance and practical utility in determining the type of the earthquake swarm,and thus be worthy of further study.
引文
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[10]刁桂苓,徐锡伟,陈于高等.汶川Mw7.9和集集Mw7.6地震前应力场转换现象及其可能的前兆意义.地球物理学报,2011,54(1):128-136.Diao G L,Xu X W,Chen Y G,et al.The precursorysignificance of tectonic stress field transformation before theWenchuan Mw7.9 Earthquake and the Chi-Chi Mw7.6Earthquake.Chinese J.Geophys.(in Chinese),2011,54(1):128-136.
[11]王俊国,刁桂苓.千岛岛弧大震前哈佛大学矩心矩张量(CMT)解一致性的预测意义.地震学报,2005,27(2):178-183.Wang J G,Diao G L.Consistent CMT solutions fromHarvard University before the great earthquakes in KurileIslands and its significance for earthquake prediction.ActaSeismologica Sinica(in Chinese),2005,27(2):178-183.
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[14]Ogata Y,Utsu T,Katsura K.Statistical discrimination offoreshocks from other earthquake clusters.Geophys.J.Int.,1996,127(1):17-30.
[15]Lund B,Bevarsson R.Correlation of microearthquake body-wave spectral amplitudes.Bull.Seism.Soc.Am.,2002,92(6):2419-2433.
[16]Brune J N.Tectonic stress and the spectra of seismic shearwaves from earthquakes.J.Geophys.Res.,1970,75(26):4997-5009.
[17]Kisslinger C,Bowman J R,Koch K.Procedures forcomputing focal mechanisms from local(SV/P)zdata.Bull.Seism.Soc.Am.,1981,71(6):1719-1729.
[18]Chael E P.Spectral scaling of earthquakes in the Miramichiregion of New Brunswick.Bull.Seism.Soc.Am.,1987,77(2):347-365.
[19]黄玉龙,郑斯华,刘杰等.广东地区地震动衰减和场地响应的研究.地球物理学报,2003,46(1):54-61.Huang Y L,Zheng S H,Liu J,et al.Attenuation of groundmotion and site response in Guangdong region.Chinese J.Geophys.(in Chinese),2003,46(1):54-61.
[20]Atkinson G M,Mereu R F.The shape of ground attenuationcurves in Southeastern Canada.Bull.Seism.Soc.Am.,1992,82(5):2014-2031.
[21]Moya A,Aguirre J,Irikura K.Inversion of sourceparameters and site effects from strong ground motion recordsusing genetic algorithms.Bull.Seism.Soc.Am.,2000,90(4):977-992.
[22]Holland J H.Adaptation in Natural and Artificial Systems.Ann Arbor:University of Michigan Press,1975.
[23]刘杰,郑斯华,黄玉龙.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,2003,25(2):211-218.Liu J,Zheng S H,Huang Y L.The inversion of non-elasticity coefficient,source parameters,site response usinggenetic algorithms.Acta Seismologica Sinica(in Chinese),2003,25(2):211-218.
[24]陈棋福,郑大林,车时等.中国震例(2000—2002).北京:地震出版社,2008.Chen Q F,Zheng D L,Che S,et al.Earthquake Cases inChina(2000—2002).Beijing:Seismological Press,2008.
[2]国家地震局预测预防司.测震学分析预报方法.北京:地震出版社,1997.Department of Prediction and Prevention for the StateSeismological Bureau.The Method of Analysis and Predictionfor the Seismometry(in Chinese).Beijing:SeismologicalPress,1997.
[3]Nur A.Dilatancy,pore fluids,and premonitory variations ofts/tptravel times.Bull.Seism.Soc.Am.,1972,62(5):1217-1222.
[4]Anderson D L,Whitcomb J H.The dilatancy-diffusion modelof earthquake prediction.∥Kovach R L,Nur A eds.Conference on Tectonic Problems of the San Anareas FaultSystem.Palo Alto:Stanford University,1973:417-426.
[5]Scholz C H,Sykes L R,Aggarwal Y P.Earthquakeprediction:aphysical basis.Science,1973,181(4102):803-810.
[6]Mjachkin V I,Brace W F,Sobolev G A,et al.Two modelsfor earthquake forerunners.Pure Appl.Geophys.,1975,113(1):169-181.
[7]陈颙.用震源机制一致性作为描述地震活动性的新参数.地球物理学报,1978,21(2):142-159.Chen Y.Consistency of focal mechanism as a new parameterin describing seismic activity.Chinese J.Geophys.(ActaGeophysica Sinica)(in Chinese),1978,21(2):142-159.
[8]刁桂苓,于新昌.唐山地震前后京、津、唐、张地区的综合断层面解.西北地震学报,1980,2(3):39-47.Diao G L,Yu X C.Composite fault plane solution before andafter the Tangshan earthquake in Beijing,Tianjin,Tangshanand Zhang.Northwestern Seismologica Journal(inChinese),1980,2(3):39-47.
[9]刁桂苓,于利民,李钦祖.强震前后震源区应力场变化一例.地震学报,1994,16(1):64-69.Diao G L,Yu L M,Li Q Z.Variation of stress field in thesource region around a strong shock:an example.ActaSeismologica Sinica(in Chinese),1994,16(1):64-69.
[10]刁桂苓,徐锡伟,陈于高等.汶川Mw7.9和集集Mw7.6地震前应力场转换现象及其可能的前兆意义.地球物理学报,2011,54(1):128-136.Diao G L,Xu X W,Chen Y G,et al.The precursorysignificance of tectonic stress field transformation before theWenchuan Mw7.9 Earthquake and the Chi-Chi Mw7.6Earthquake.Chinese J.Geophys.(in Chinese),2011,54(1):128-136.
[11]王俊国,刁桂苓.千岛岛弧大震前哈佛大学矩心矩张量(CMT)解一致性的预测意义.地震学报,2005,27(2):178-183.Wang J G,Diao G L.Consistent CMT solutions fromHarvard University before the great earthquakes in KurileIslands and its significance for earthquake prediction.ActaSeismologica Sinica(in Chinese),2005,27(2):178-183.
[12]Sobolev G A.Physical processes during the earthquakepreparation period:experiment and theory,earthquakeprediction.Proceedings of International Symposium onearthquake Prediction(1979).Pariss:Uness Co,1984:281-310.
[13]Ogata Y,Utsu T,Katsura K.Statistical features offoreshocks in comparison with other earthquake clusters.Geophys.J.Int.,1995,121(1):233-254.
[14]Ogata Y,Utsu T,Katsura K.Statistical discrimination offoreshocks from other earthquake clusters.Geophys.J.Int.,1996,127(1):17-30.
[15]Lund B,Bevarsson R.Correlation of microearthquake body-wave spectral amplitudes.Bull.Seism.Soc.Am.,2002,92(6):2419-2433.
[16]Brune J N.Tectonic stress and the spectra of seismic shearwaves from earthquakes.J.Geophys.Res.,1970,75(26):4997-5009.
[17]Kisslinger C,Bowman J R,Koch K.Procedures forcomputing focal mechanisms from local(SV/P)zdata.Bull.Seism.Soc.Am.,1981,71(6):1719-1729.
[18]Chael E P.Spectral scaling of earthquakes in the Miramichiregion of New Brunswick.Bull.Seism.Soc.Am.,1987,77(2):347-365.
[19]黄玉龙,郑斯华,刘杰等.广东地区地震动衰减和场地响应的研究.地球物理学报,2003,46(1):54-61.Huang Y L,Zheng S H,Liu J,et al.Attenuation of groundmotion and site response in Guangdong region.Chinese J.Geophys.(in Chinese),2003,46(1):54-61.
[20]Atkinson G M,Mereu R F.The shape of ground attenuationcurves in Southeastern Canada.Bull.Seism.Soc.Am.,1992,82(5):2014-2031.
[21]Moya A,Aguirre J,Irikura K.Inversion of sourceparameters and site effects from strong ground motion recordsusing genetic algorithms.Bull.Seism.Soc.Am.,2000,90(4):977-992.
[22]Holland J H.Adaptation in Natural and Artificial Systems.Ann Arbor:University of Michigan Press,1975.
[23]刘杰,郑斯华,黄玉龙.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,2003,25(2):211-218.Liu J,Zheng S H,Huang Y L.The inversion of non-elasticity coefficient,source parameters,site response usinggenetic algorithms.Acta Seismologica Sinica(in Chinese),2003,25(2):211-218.
[24]陈棋福,郑大林,车时等.中国震例(2000—2002).北京:地震出版社,2008.Chen Q F,Zheng D L,Che S,et al.Earthquake Cases inChina(2000—2002).Beijing:Seismological Press,2008.
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