川滇地区强震活动前b值的时空分布特征
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摘要
由于地震活动性参数b值能够反映地壳环境应力的大小,因此基于b值的地震活动性图像研究成为地震预测研究和实践最直观明了的方法之一。川滇地区地震活动频繁,是检验各种地震预测方法的理想实验场。为了研究川滇地区b值分布与强震活动的关系,利用过去40多年的小震资料分析了该区域1981年以来19次M6.5地震与b值的时空分布关系。结果表明:虽然川滇地区b值空间分布特征与强震活动之间关系并不显著,不到50%的强震发生在b值小于区域平均值的地区,但是震前b值的时间分布呈现系统地下降,58%的震源区的b值在强震前出现显著下降趋势。结合其他的地震、地质资料,较短时间内的地震活动性资料可以为特定地区的地震潜在危险性的判定提供一定的启示。
Because b-value can be used as an indicator to measure the level of crustal stress,the seismicity pattern recognition based on b-value is considered as one of the most intuitive methods for earthquake forecast research and experiments. The intense seismicity in the Sichuan-Yunnan region makes the ar- ea to be an ideal field for earthquake forecast experiment. We investigated the spatial and temporal variations of b-values before nineteen earthquakes with M≥6. 5 in the Sichuan-Yunnan region from 1981 to 2008 using regional small earthquake data. The results show that spatial b-value variations portending M≥6. 5 earthquakes in the Sichuan-Yunnan region are insignificant. Less than 50% of the major earthquakes occurred in the regions with low b-values relative to the entire study area. In terms of temporal evolutions,the b-values in seismic source regions showed a systematic drop before the oc- currence of earthquake. They showed an obvious decreasing trend during the period one year prior to strong earthquakes in 58% of the seismic source regions. Combined with other geological and seismo- logical data,the short-term seismicity data can provide certain enlightenment for the estimation of po- tential seismic hazard in specific regions.
Because b-value can be used as an indicator to measure the level of crustal stress,the seismicity pattern recognition based on b-value is considered as one of the most intuitive methods for earthquake forecast research and experiments. The intense seismicity in the Sichuan-Yunnan region makes the ar- ea to be an ideal field for earthquake forecast experiment. We investigated the spatial and temporal variations of b-values before nineteen earthquakes with M≥6. 5 in the Sichuan-Yunnan region from 1981 to 2008 using regional small earthquake data. The results show that spatial b-value variations portending M≥6. 5 earthquakes in the Sichuan-Yunnan region are insignificant. Less than 50% of the major earthquakes occurred in the regions with low b-values relative to the entire study area. In terms of temporal evolutions,the b-values in seismic source regions showed a systematic drop before the oc- currence of earthquake. They showed an obvious decreasing trend during the period one year prior to strong earthquakes in 58% of the seismic source regions. Combined with other geological and seismo- logical data,the short-term seismicity data can provide certain enlightenment for the estimation of po- tential seismic hazard in specific regions.
引文
黄玮琼,李文香.1998.地震区划中b值统计时空范围的确定[J].地震学报,20(5):449—453.
HUANG Wei-qiong,LI Wen-xiang.1998.Determining the time and space domains for estimating b value in seismiczone[J].Acta Seismologica Sinica,11(5):517—522.
刘瑞丰,陈运泰,Bormann P,等.2006.中国地震台网与美国地震台网测定震级的对比Ⅱ:面波震级[J].地震学报,28(1):1—7.LIU Rui-feng,CHEN Yun-tai,Bormann P,et al.2006.Comparison between earthquake magnitudes determined by Chinaseismograph network and U.S.seismograph network(2):Surface wave magnitude[J].Acta Seismologica Sinica,28(1):1—7(in Chinese).
马瑾,雷兴林,焦文捷,等.1990.京津唐张地区震级频度关系的空间扫描[J].地震地质,12(3):229—236.MA Jin,LEI Xing-lin,JIAO Wen-jie,et al.1990.The spatial scanning of the frequency-magnitude distribution of earth-quakes in Beijing-Tianjin-Tangshan-Zhangjiakou area[J].Seismology and Geology,12(3):229—236(in Chi-nese).
冉洪流,何宏林.2006.鲜水河断裂带北西段不同破裂源强震震级(M>6.7)及复发间隔研究[J].地球物理学报,49(1):153—161.RAN Hong-liu,HE Hong-lin.2006.Research on the magnitude and recurrence interval of characterized earthquakeswith magnitude≥6.7along the northwestern portion of the Xianshuihe Fault zone in western Sichuan,China[J].Chinese Journal of Geophysics,49(1):153—161(in Chinese).
苏有锦,李永莉,李忠华,等.2003.川滇地区区域地震目录完整性最小震级分析[J].地震研究,26(增刊):10—16.SU You-jin,LI Yong-li,LI Zhong-hua,et al.2003.Analysis of minimum complete magnitude of earthquake catalog in Si-chuan-Yunnan region[J].Journal of Seimological Research,26(suppl):10—16(in Chinese).
向宏发,虢顺民,徐锡伟,等.2000.川滇南部地区活动地块划分与现今运动特征初析[J].地震地质,22(3):253—264.XIANG Hong-fa,GUO Shun-min,XU Xi-wei,et al.2000.Active block division and present-day motion features of thesouth region of Sichuan-Yunnan Provinces[J].Seismology and Geology,22(3):253—264(in Chinese).
易桂喜,闻学泽,王思维,等.2006.由地震活动参数分析龙门山-岷山断裂带的现今活动习性与强震危险性[J].中国地震,22(2):117—125.YI Gui-xi,WEN Xue-ze,WANG Si-wei,et al.2006.Study on fault sliding behaviors and strong-earthquake risk of theLongmenshan-Minshan Fault zones from current seismicity parameters[J].Earthquake Research in China,22(2):117—125(in Chinese).
易桂喜,闻学泽,苏有锦.2008.川滇活动地块东边界强震危险性研究[J].地球物理学报,51(6):1719—1725.YI Gui-xi,WEN Xue-ze,SU You-jin.2008.Study on the potential strong-earthquake risk for the eastern boundary of theSichuan-Yunnan active faulted-block,China[J].Chinese Journal of Geophysics,51(6):1719—1725(in Chi-nese).
易桂喜,闻学泽,辛华,等.2011.2008年汶川MS8.0地震前龙门山-岷山构造带的地震活动性参数与地震视应力分布[J].地球物理学报,54(6):1490—1500.doi:10.3969/j.issn.0001-5733.2011.06.008.YI Gui-xi,WEN Xue-ze,XIN Hua,et al.2011.Distributions of seismicity parameters and seismic apparent stresses onthe Longmenshan-Minshan tectonic zone before2008MS8.0Wenchuan earthquake[J].Chinese Journal of Geo-physics,54(6):1490—1500(in Chinese).
朱艾斓,徐锡伟,甘卫军,等.2009.鲜水河-安宁河-则木河断裂带上可能存在的凹凸体:来自背景地震活动性的证据[J].地学前缘,16(1):218—225.ZHU Ai-lan,XU Xi-wei,GAN Wei-jun,et al.2009.The possible asperities on the Xianshuihe-Anninghe-Zemuhe Faultzone:Evidence from background seismicity[J].Earth Science Frontiers,16(1):218—225(in Chinese).
Allen C R,Luo Z,Qian H,et al.1991.Field study of a highly active fault zone:the Xianshuihe Fault zone of southwest-ern China[J].Geological Society of America Bulletin,103:1178—1199.
Amitrano D.2003.Brittle-ductile transition and associated seismicity:Experimental and numerical studies and relation-ship with the b value[J].Journal of Geophysical Research-Solid Earth,108(B1,2044).doi:10.1029/2001JB00680.
Chan C H,Wu Y M,Tseng T L,et al.2012.Spatial and temporal evolution of b-values before large earthquakes in Tai-wan[J].Tectonophysics,532-535:215—222.doi:10.1016/j.tecto.2012.02.004.
Christophersen A,Smith E G.2008.Foreshock rates from aftershock abundance[J].Bulletin of the Seismological Socie-ty of America,98(5):2133—2148.doi:10.1785/0120060143.
Densmore A L,Ellis M A,Li Y,et al.2007.Active tectonics of the Beichuan and Pengguan Faults at the eastern marginof the Tibetan Plateau[J].Tectonics,26(TC4005).doi:10.1029/2006TC001987.
Gardner J K,Knopoff L.1974.Is the sequence of earthquakes in Southern California,with aftershocks removed,Poisso-nian?[J].Bulletin of the Seismological Society of America,64:1363—1367.
Gutenberg B,Richter C R.1954.Magnitude and energy of earthquakes[J].Ann Geofis,9:1—15.
Huang Q.2008.Seismicity changes prior to the MS8.0Wenchuan earthquake in Sichuan,China[J].Geophysical Re-search Letters,35(L23308).doi:10.1029/2008GL036270.
Lei X,Masuda K,Nishizawa O,et al.2004.Detailed analysis of acoustic emission activity during catastrophic fracture offaults in rock[J].Journal of Structural Geology,26(2):247—258.doi:10.1016/S0191-8141(03)00095—6.
Meade B J.2007.Present-day kinematics at the India-Asia collision zone[J].Geology,35(1):81—84.doi:10.1130/G22924A.1.
Reasenberg P.1985.Second-order moment of central California seismicity[J].Journal of Geophysical Research,90(B7):5479—5495.
Royden L H,Burchfiel B C,Van der Hilst R D.2008.The geological evolution of the Tibetan Plateau[J].Science,321:1054—1058.doi:10.1126/science.1155371.
Rundle J B,Turcotte D L,Shcherbakov R,et al.2003.Statistical physics approach to understanding the multiscale dy-namics of earthquake fault systems[J].Reviews of Geophysics,41(4):1019.
Scholz C H.1968.The frequency-magnitude relation of microfracturing in rock and its relation to earthquakes[J].Bul-letin of the Seismological Society of America,58(1):399—415.
Schorlemmer D,Wiemer S,Wyss M.2005.Variations in earthquake-size distribution across different stress regimes[J].Nature,437:539—542,doi:10.1038/nature04094.
Shi Y,Bolt B A.1982.The standard error of the magnitude-frequency b value[J].Bulletin of the Seismological Societyof America,72(5):1677—1687.
Smith W D.1981.The b-value as an earthquake precursor[J].Nature,289:136—139.doi:10.1038/289136a0.
Uhrhammer R.1986.Characteristics of northern and southern California seismicity[J].Earthquake Notes,57(21).
Utsu T,Seki A.1955.A relation between the area of aftershock region and the energy of the mainshock[J].Zisin,7:233—240(in Japanese with English abstract).
Wang H,Liu M,Shen X,et al.2010.Balance of seismic moment in the Songpan-Ganze region,eastern Tibet:Implica-tions for the2008great Wenchuan earthquake[J].Tectonophysics,491:154—164.doi:10.1016/j.tecto.2009-09.022.
Wen X,Ma S,Xu X,et al.2008.Historical pattern and behavior of earthquake ruptures along the eastern boundary ofthe Sichuan-Yunnan faulted-block,southwestern China[J].Physics of the Earth and Planetary Interiors,168:16—36.doi:10.1016/j.pepi.2008.04.013.
Wiemer S,Wyss M.2000.Minimum magnitude of completeness in earthquake catalogs:Examples from Alaska,thewestern US and Japan[J].Bulletin of the Seismological Society of America,90(4):859—869.
Wiemer S,Schorlemmer D.2007.ALM:An asperity-based likelihood model for California[J].Seismological ResearchLetters,78(1):134—140.
Zhang P,Yang Z,Gupta H K,et al.1999.Global seismic hazard assessment program(GSHAP)in continental Asia[J].Annali Di Geofisica,42(6):1167—1190.
HUANG Wei-qiong,LI Wen-xiang.1998.Determining the time and space domains for estimating b value in seismiczone[J].Acta Seismologica Sinica,11(5):517—522.
刘瑞丰,陈运泰,Bormann P,等.2006.中国地震台网与美国地震台网测定震级的对比Ⅱ:面波震级[J].地震学报,28(1):1—7.LIU Rui-feng,CHEN Yun-tai,Bormann P,et al.2006.Comparison between earthquake magnitudes determined by Chinaseismograph network and U.S.seismograph network(2):Surface wave magnitude[J].Acta Seismologica Sinica,28(1):1—7(in Chinese).
马瑾,雷兴林,焦文捷,等.1990.京津唐张地区震级频度关系的空间扫描[J].地震地质,12(3):229—236.MA Jin,LEI Xing-lin,JIAO Wen-jie,et al.1990.The spatial scanning of the frequency-magnitude distribution of earth-quakes in Beijing-Tianjin-Tangshan-Zhangjiakou area[J].Seismology and Geology,12(3):229—236(in Chi-nese).
冉洪流,何宏林.2006.鲜水河断裂带北西段不同破裂源强震震级(M>6.7)及复发间隔研究[J].地球物理学报,49(1):153—161.RAN Hong-liu,HE Hong-lin.2006.Research on the magnitude and recurrence interval of characterized earthquakeswith magnitude≥6.7along the northwestern portion of the Xianshuihe Fault zone in western Sichuan,China[J].Chinese Journal of Geophysics,49(1):153—161(in Chinese).
苏有锦,李永莉,李忠华,等.2003.川滇地区区域地震目录完整性最小震级分析[J].地震研究,26(增刊):10—16.SU You-jin,LI Yong-li,LI Zhong-hua,et al.2003.Analysis of minimum complete magnitude of earthquake catalog in Si-chuan-Yunnan region[J].Journal of Seimological Research,26(suppl):10—16(in Chinese).
向宏发,虢顺民,徐锡伟,等.2000.川滇南部地区活动地块划分与现今运动特征初析[J].地震地质,22(3):253—264.XIANG Hong-fa,GUO Shun-min,XU Xi-wei,et al.2000.Active block division and present-day motion features of thesouth region of Sichuan-Yunnan Provinces[J].Seismology and Geology,22(3):253—264(in Chinese).
易桂喜,闻学泽,王思维,等.2006.由地震活动参数分析龙门山-岷山断裂带的现今活动习性与强震危险性[J].中国地震,22(2):117—125.YI Gui-xi,WEN Xue-ze,WANG Si-wei,et al.2006.Study on fault sliding behaviors and strong-earthquake risk of theLongmenshan-Minshan Fault zones from current seismicity parameters[J].Earthquake Research in China,22(2):117—125(in Chinese).
易桂喜,闻学泽,苏有锦.2008.川滇活动地块东边界强震危险性研究[J].地球物理学报,51(6):1719—1725.YI Gui-xi,WEN Xue-ze,SU You-jin.2008.Study on the potential strong-earthquake risk for the eastern boundary of theSichuan-Yunnan active faulted-block,China[J].Chinese Journal of Geophysics,51(6):1719—1725(in Chi-nese).
易桂喜,闻学泽,辛华,等.2011.2008年汶川MS8.0地震前龙门山-岷山构造带的地震活动性参数与地震视应力分布[J].地球物理学报,54(6):1490—1500.doi:10.3969/j.issn.0001-5733.2011.06.008.YI Gui-xi,WEN Xue-ze,XIN Hua,et al.2011.Distributions of seismicity parameters and seismic apparent stresses onthe Longmenshan-Minshan tectonic zone before2008MS8.0Wenchuan earthquake[J].Chinese Journal of Geo-physics,54(6):1490—1500(in Chinese).
朱艾斓,徐锡伟,甘卫军,等.2009.鲜水河-安宁河-则木河断裂带上可能存在的凹凸体:来自背景地震活动性的证据[J].地学前缘,16(1):218—225.ZHU Ai-lan,XU Xi-wei,GAN Wei-jun,et al.2009.The possible asperities on the Xianshuihe-Anninghe-Zemuhe Faultzone:Evidence from background seismicity[J].Earth Science Frontiers,16(1):218—225(in Chinese).
Allen C R,Luo Z,Qian H,et al.1991.Field study of a highly active fault zone:the Xianshuihe Fault zone of southwest-ern China[J].Geological Society of America Bulletin,103:1178—1199.
Amitrano D.2003.Brittle-ductile transition and associated seismicity:Experimental and numerical studies and relation-ship with the b value[J].Journal of Geophysical Research-Solid Earth,108(B1,2044).doi:10.1029/2001JB00680.
Chan C H,Wu Y M,Tseng T L,et al.2012.Spatial and temporal evolution of b-values before large earthquakes in Tai-wan[J].Tectonophysics,532-535:215—222.doi:10.1016/j.tecto.2012.02.004.
Christophersen A,Smith E G.2008.Foreshock rates from aftershock abundance[J].Bulletin of the Seismological Socie-ty of America,98(5):2133—2148.doi:10.1785/0120060143.
Densmore A L,Ellis M A,Li Y,et al.2007.Active tectonics of the Beichuan and Pengguan Faults at the eastern marginof the Tibetan Plateau[J].Tectonics,26(TC4005).doi:10.1029/2006TC001987.
Gardner J K,Knopoff L.1974.Is the sequence of earthquakes in Southern California,with aftershocks removed,Poisso-nian?[J].Bulletin of the Seismological Society of America,64:1363—1367.
Gutenberg B,Richter C R.1954.Magnitude and energy of earthquakes[J].Ann Geofis,9:1—15.
Huang Q.2008.Seismicity changes prior to the MS8.0Wenchuan earthquake in Sichuan,China[J].Geophysical Re-search Letters,35(L23308).doi:10.1029/2008GL036270.
Lei X,Masuda K,Nishizawa O,et al.2004.Detailed analysis of acoustic emission activity during catastrophic fracture offaults in rock[J].Journal of Structural Geology,26(2):247—258.doi:10.1016/S0191-8141(03)00095—6.
Meade B J.2007.Present-day kinematics at the India-Asia collision zone[J].Geology,35(1):81—84.doi:10.1130/G22924A.1.
Reasenberg P.1985.Second-order moment of central California seismicity[J].Journal of Geophysical Research,90(B7):5479—5495.
Royden L H,Burchfiel B C,Van der Hilst R D.2008.The geological evolution of the Tibetan Plateau[J].Science,321:1054—1058.doi:10.1126/science.1155371.
Rundle J B,Turcotte D L,Shcherbakov R,et al.2003.Statistical physics approach to understanding the multiscale dy-namics of earthquake fault systems[J].Reviews of Geophysics,41(4):1019.
Scholz C H.1968.The frequency-magnitude relation of microfracturing in rock and its relation to earthquakes[J].Bul-letin of the Seismological Society of America,58(1):399—415.
Schorlemmer D,Wiemer S,Wyss M.2005.Variations in earthquake-size distribution across different stress regimes[J].Nature,437:539—542,doi:10.1038/nature04094.
Shi Y,Bolt B A.1982.The standard error of the magnitude-frequency b value[J].Bulletin of the Seismological Societyof America,72(5):1677—1687.
Smith W D.1981.The b-value as an earthquake precursor[J].Nature,289:136—139.doi:10.1038/289136a0.
Uhrhammer R.1986.Characteristics of northern and southern California seismicity[J].Earthquake Notes,57(21).
Utsu T,Seki A.1955.A relation between the area of aftershock region and the energy of the mainshock[J].Zisin,7:233—240(in Japanese with English abstract).
Wang H,Liu M,Shen X,et al.2010.Balance of seismic moment in the Songpan-Ganze region,eastern Tibet:Implica-tions for the2008great Wenchuan earthquake[J].Tectonophysics,491:154—164.doi:10.1016/j.tecto.2009-09.022.
Wen X,Ma S,Xu X,et al.2008.Historical pattern and behavior of earthquake ruptures along the eastern boundary ofthe Sichuan-Yunnan faulted-block,southwestern China[J].Physics of the Earth and Planetary Interiors,168:16—36.doi:10.1016/j.pepi.2008.04.013.
Wiemer S,Wyss M.2000.Minimum magnitude of completeness in earthquake catalogs:Examples from Alaska,thewestern US and Japan[J].Bulletin of the Seismological Society of America,90(4):859—869.
Wiemer S,Schorlemmer D.2007.ALM:An asperity-based likelihood model for California[J].Seismological ResearchLetters,78(1):134—140.
Zhang P,Yang Z,Gupta H K,et al.1999.Global seismic hazard assessment program(GSHAP)in continental Asia[J].Annali Di Geofisica,42(6):1167—1190.
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