用钻孔应变观测研究北京地区活断层的现今活动
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摘要
研究断层活动性的主要目的之一是了解地震危险性,与地震危险性最直接相关的是现今的断层活动情况。如果对当地断层分布和性质有比较清楚的了解,那么就可以根据位错理论用钻孔应变仪观测资料反演断层活动。用遗传算法进行这种反演可以在进行全局搜索的同时大大提高计算效率。北京地区的活断层研究程度比较高,同时有比较密集的钻孔应变观测台站。利用2003—2005年钻孔应变观测资料对北京地区活断层活动的初步尝试性反演表明,在此期间顺义-良乡断层北段和南口-孙河断层东南段的活动可能起主导作用,活动程度与小震活动有关系。
One of the principal goals of studying active faults is to understand the possibility of earthquakes.Contemporary faults' activities are most important from this point of view.When a fault slips,the surrounding strain field changes.The linear elastic dislocation theory provides a powerful tool to solve problems associated with strain field changes due to fault slip.In some widely acknowledged studies in fields such as interpreting InSAR pattern of seismic fault slip and analyzing stress transfer or stress trigger of earthquakes,dislocation theory is always the first selection of researchers.Inversion with data from observatory stations is a common method in geophysical research.It can be used with recordings by borehole strainmeters as well as by seismometers.We introduce in this paper an approach of inverting contemporary fault slip with continuous data recorded by borehole strainmeters.Since relatively more stations are located in Beijing area and more and better studies about active faults here are documented,we have,as an attempt,carried out a practical inversion over this region of the faults' possible slips.In our problem here,known conditions include observations from several stations and distribution as well as senses of the faults.We calculated the slips of the faults.Apart from contributions of the local faults,the strain field is also affected by background tectonic deformation,whose influence is assumed to be evenly distributed over the study area.We examined influences of errors in Poisson ratio and fault parameters such as dip,strike,length and depth.The result shows that Poisson ratio's error can be ignored;while,within the searching extent,changes in fault parameters only affect adjacent areas of the faults significantly.In contrast,fault slip plays an overwhelmingly important role in determining amplitudes of strains at all the points.Since there are numerous faults of various sizes and shapes,and with inhomogeneous dislocation distributions,in the earth's crust,one may take our results of inversion as a predominant effect of the faults.We pointed out that only 9 stations are referred to and many parameters are involved in our study.Therefore,the result is with remarkable uncertainty.We can improve the inversion when there is a denser borehole strainmeter network.
One of the principal goals of studying active faults is to understand the possibility of earthquakes.Contemporary faults' activities are most important from this point of view.When a fault slips,the surrounding strain field changes.The linear elastic dislocation theory provides a powerful tool to solve problems associated with strain field changes due to fault slip.In some widely acknowledged studies in fields such as interpreting InSAR pattern of seismic fault slip and analyzing stress transfer or stress trigger of earthquakes,dislocation theory is always the first selection of researchers.Inversion with data from observatory stations is a common method in geophysical research.It can be used with recordings by borehole strainmeters as well as by seismometers.We introduce in this paper an approach of inverting contemporary fault slip with continuous data recorded by borehole strainmeters.Since relatively more stations are located in Beijing area and more and better studies about active faults here are documented,we have,as an attempt,carried out a practical inversion over this region of the faults' possible slips.In our problem here,known conditions include observations from several stations and distribution as well as senses of the faults.We calculated the slips of the faults.Apart from contributions of the local faults,the strain field is also affected by background tectonic deformation,whose influence is assumed to be evenly distributed over the study area.We examined influences of errors in Poisson ratio and fault parameters such as dip,strike,length and depth.The result shows that Poisson ratio's error can be ignored;while,within the searching extent,changes in fault parameters only affect adjacent areas of the faults significantly.In contrast,fault slip plays an overwhelmingly important role in determining amplitudes of strains at all the points.Since there are numerous faults of various sizes and shapes,and with inhomogeneous dislocation distributions,in the earth's crust,one may take our results of inversion as a predominant effect of the faults.We pointed out that only 9 stations are referred to and many parameters are involved in our study.Therefore,the result is with remarkable uncertainty.We can improve the inversion when there is a denser borehole strainmeter network.
引文
陈连旺,陆远忠,张杰,等.1999.华北地区三维构造应力场[J].地震学报,21(2):140—149.CHEN Lian-wang,LU Yuan-zhong,ZHANG Jie,et al.1999.Three dimensional tectonic stress field in North China[J].Acta Seismologica Sinica,21(2):140—149(in Chinese).
焦青,邱泽华.2006.北京平原地区主要活动断裂带研究概况[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(18).北京:地震出版社.72—84.JIAO Qing,QIU Ze-hua.2006.Progress in research of major active faults in Beijing area[A].In:Institute of CrustalDynamics of China Earthquake Administration(ed).Bulletin of the Institute of Crustal Dynamics(18).Seismo-logical Press,Beijing.72—84(in Chinese).
罗焕炎,宋惠珍,潘善德,等.1980.渤海及其邻区现代地壳构造应力场与地震关系的数字模拟[J].见:张文佑主编.华北断块区的形成与发展.北京:科学出版杜.252—260.LUO Huan-yan,SONG Hui-zhen,PAN Shan-de,et al.1980.Numerical simulation of recent crust stress field relatingto seismicities in Northern China bay area and its surroundings[A].In:ZHANG Wen-you(ed).Formation anddevelopment of the North China fault block region.Science Press,Beijing.252—260(in Chinese).
骆鸣津,顾梦林,李安印,等.1989.用引潮力进行钻孔应变-应力的原地标定[J].地壳形变与地震,9(4):51-62.LUO Ming-jin,GU Meng-lin,LI An-yin,et al.1989.Borehole strain-stress calibration in the same place by use of tidalgeneration force[J].Crustal Deformation and Earthquake,9(4):51—62(in Chinese).
邱泽华,石耀霖.2003.地震造成远距离应力阶变的观测实例[J].中国科学(D辑),33(增刊):60—64.QIU Ze-hua,SHI Yao-lin.2003.Observations of remote coseismic stress step-changes[J].Science in China(SerD),46(Suppl):75—81.
邱泽华,石耀霖.2004.观测应变阶在地震应力触发研究中的应用[J].地震学报,26(5):481—488.QIU Ze-hua,SHI Yao-lin.2004.Application of observed strain steps to the study of remote earthquake stress triggering[J].Acta Seismologica Sinica,17(5):534—541.
邱泽华,石耀霖,欧阳祖熙.2005a.四分量钻孔应变观测的实地相对标定[J].大地测量与地球动力学,25(1):118-122.QIU Ze-hua,SHI Yao-lin,OUYANG Zu-xi.2005a.Relative in-situ calibration of4-component borehole strainmeter[J].Journal of Geodesy and Geodynamics,25(1):118—122(in Chinese).
邱泽华,石耀霖,欧阳祖熙.2005b.四分量钻孔应变观测的实地绝对标定[J].地震,25(3):27—34.QIU Ze-hua,SHI Yao-lin,OUYANG Zu-xi.2005b.Absolute calibration of4-component borehole strainmeter[J].Earthquake,25(3):27—34(in Chinese).
邱泽华.2006.地面应变场变化图像的观测[J].国际地震动态,6:7—11.QIU Ze-hua.2006.Observation of changing pattern of the surficial strain field[J].Recent Developments in WorldSeismology,6:7—11(in Chinese).
石耀霖.1992.遗传算法在地球物理中的应用[J].地球物理学报,35(增刊):367—371.SHI Yao-lin.1992.Application of genetic algorithms in the field of geophysics[J].Chinese Journal of Geophysics,35(Suppl):367—371(in Chinese).
石耀霖,金文.1995.面波频散反演地球内部构造的遗传算法[J].地球物理学报,38(2):189—198.SHI Yao-lin,JIN Wen.1995.Genetic algorithms inversion of lithospheric structure from surface wave dispersion[J].Chinese Journal of Geophysics,38(2):189—198(in Chinese).
宋惠珍,高维安,孙君秀,等.1982.唐山地震震源应力场的数值模拟研究[J].西北地震学报,4(3):50—56.SONG Hui-zhen,GAO Wei-an,SUN Jun-xiu,et al.1982.Numerical analysis of stress field of Tangshan area applyingthree dimensional finite element method to compute focal stress field[J].Northwestern Seismological Journal,4(3):50—56(in Chinese).
苏恺之,刘瑞民,裴玉珍,等.1987.液位型和液压型体积式应变仪[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(1).北京:地震出版社.131—135.SU Kai-zhi,LIU Rui-min,PEI Yu-zhen,et al.1987.Hydraulic level type and hydraulic pressure type dilatometers[A].In:Institute of Crustal Dynamics of China Earthquake Administration(ed).Bulletin of the Institute ofCrustal Dynamics(1).Seismological Press,Beijing.131—135(in Chinese).
苏恺之.2003.地应变观测的物理解释-漂移、噪声和突跳[A].见:苏恺之等编.钻孔地应变观测新进展.北京:地震出版社.95—110.SU Kai-zhi.2003.Physical explanation of strain observation-shift,noise and pulsation[A].In:SU Kai-zhiet al.(eds).New developments in the observation with borehole strainmeters.Seismological Press,Beijing.95—110(in Chinese).
王仁,黄杰藩,孙荀英,等.1982.华北地震构造应力场的模拟[J].中国科学(B辑),4:337—344.WANG Ren,HUANG Jie-fan,SUNXun-ying,et al.1982.Simulation of the tectonic stress field over North China[J].Science in China(Ser B),4:337—344(in Chinese).
汪素云,陈培善.1980.中国及邻区现代构造应力场的数值模拟[J].地球物理学报,23(1):35—45.WANG Su-yun,CHEN Pei-shan.1980.A numerical simulation of the present tectonic stress field of China and its vic-inity[J].Acta Geophysica Sinica,23(1):35—45(in Chinese).
易志刚,邱泽华,宋茉.2006.首都圈地区数字化钻孔应变观测资料分析[J].大地测量与地球动力学,26(3):53—58.YI Zhi-gang,QIU Ze-hua,SONG Mo.2006.Analysis of digital recordings of borehole strainmeters in the Capital area[J].Journal of Geodesy and Geodynamics,26(3):53—58(in Chinese).
张东宁,高龙生.1989.东亚地区应力场的三维数值模拟[J].中国地震,5(4):24—33.ZHANG Dong-ning,GAO Long-sheng.1989.Three dimensional numerical simulation of eastern Asian stress field[J].Earthquake Research in China,5(4):24—33(in Chinese).
Hart R HG,Gladwin MT,Gwyther R L,et al.1996.Tidal calibration of borehole strain metrics:Removing the effectsof small-scale inhomogeneity[J].J Geophy Res,101(B11):25553—25571.
Hill D P,Reasonberg P A,Michael A,et al.1993.Seismicity remotely triggered by the magnitude7·3Landers,Cali-fornia earthquake[J].Science,260:1617—1623.
Ishii H,Yamauchi T,Matsumoto S,et al.2002.Development of multi-component borehole instrument for earthquakeprediction study:some observed examples of precursory and co-seismic phenomena relating to earthquake swarmsand application of the instrument for rock mechanics[A].In:Ogasawara Het al(eds).Seismic Process Monito-ring.Rotterdam:Balkema,365—377.
Linde A T,Gladwin MT,Johnston MJ S,et al.1996.A slowearthquake sequence near San Juan Bautista,Californiain December1992[J].Nature,383:65—69.
Massonnet D,Rossi M,Carmona C,et al.1993.The displacement field of the Landers earthquake mapped by radar in-terferometry[J].Nature,364:138—142.
Okada Y.1985.Surface deformation due to shear and tensile faults in a half-space[J].Bull Seism Soc Am,75:1135—1154.
Okada Y.1992.Internal deformation due to shear and tensile faults in a half-space[J].Bull Seis Soc Am,82:1018—1040.
Sacks I S,Suyehiro S,Evertson D W,et al.1971.Sacks-Evertson strainmeter,its installation in Japan and some pre-liminary results concerning strain steps[J].Pap Met Geophys,22:195—207.
Sacks I S,Suyehiro S,Linde A T,et al.1978.Slow earthquake and stress distribution[J].Nature,275:5681,599—602.
焦青,邱泽华.2006.北京平原地区主要活动断裂带研究概况[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(18).北京:地震出版社.72—84.JIAO Qing,QIU Ze-hua.2006.Progress in research of major active faults in Beijing area[A].In:Institute of CrustalDynamics of China Earthquake Administration(ed).Bulletin of the Institute of Crustal Dynamics(18).Seismo-logical Press,Beijing.72—84(in Chinese).
罗焕炎,宋惠珍,潘善德,等.1980.渤海及其邻区现代地壳构造应力场与地震关系的数字模拟[J].见:张文佑主编.华北断块区的形成与发展.北京:科学出版杜.252—260.LUO Huan-yan,SONG Hui-zhen,PAN Shan-de,et al.1980.Numerical simulation of recent crust stress field relatingto seismicities in Northern China bay area and its surroundings[A].In:ZHANG Wen-you(ed).Formation anddevelopment of the North China fault block region.Science Press,Beijing.252—260(in Chinese).
骆鸣津,顾梦林,李安印,等.1989.用引潮力进行钻孔应变-应力的原地标定[J].地壳形变与地震,9(4):51-62.LUO Ming-jin,GU Meng-lin,LI An-yin,et al.1989.Borehole strain-stress calibration in the same place by use of tidalgeneration force[J].Crustal Deformation and Earthquake,9(4):51—62(in Chinese).
邱泽华,石耀霖.2003.地震造成远距离应力阶变的观测实例[J].中国科学(D辑),33(增刊):60—64.QIU Ze-hua,SHI Yao-lin.2003.Observations of remote coseismic stress step-changes[J].Science in China(SerD),46(Suppl):75—81.
邱泽华,石耀霖.2004.观测应变阶在地震应力触发研究中的应用[J].地震学报,26(5):481—488.QIU Ze-hua,SHI Yao-lin.2004.Application of observed strain steps to the study of remote earthquake stress triggering[J].Acta Seismologica Sinica,17(5):534—541.
邱泽华,石耀霖,欧阳祖熙.2005a.四分量钻孔应变观测的实地相对标定[J].大地测量与地球动力学,25(1):118-122.QIU Ze-hua,SHI Yao-lin,OUYANG Zu-xi.2005a.Relative in-situ calibration of4-component borehole strainmeter[J].Journal of Geodesy and Geodynamics,25(1):118—122(in Chinese).
邱泽华,石耀霖,欧阳祖熙.2005b.四分量钻孔应变观测的实地绝对标定[J].地震,25(3):27—34.QIU Ze-hua,SHI Yao-lin,OUYANG Zu-xi.2005b.Absolute calibration of4-component borehole strainmeter[J].Earthquake,25(3):27—34(in Chinese).
邱泽华.2006.地面应变场变化图像的观测[J].国际地震动态,6:7—11.QIU Ze-hua.2006.Observation of changing pattern of the surficial strain field[J].Recent Developments in WorldSeismology,6:7—11(in Chinese).
石耀霖.1992.遗传算法在地球物理中的应用[J].地球物理学报,35(增刊):367—371.SHI Yao-lin.1992.Application of genetic algorithms in the field of geophysics[J].Chinese Journal of Geophysics,35(Suppl):367—371(in Chinese).
石耀霖,金文.1995.面波频散反演地球内部构造的遗传算法[J].地球物理学报,38(2):189—198.SHI Yao-lin,JIN Wen.1995.Genetic algorithms inversion of lithospheric structure from surface wave dispersion[J].Chinese Journal of Geophysics,38(2):189—198(in Chinese).
宋惠珍,高维安,孙君秀,等.1982.唐山地震震源应力场的数值模拟研究[J].西北地震学报,4(3):50—56.SONG Hui-zhen,GAO Wei-an,SUN Jun-xiu,et al.1982.Numerical analysis of stress field of Tangshan area applyingthree dimensional finite element method to compute focal stress field[J].Northwestern Seismological Journal,4(3):50—56(in Chinese).
苏恺之,刘瑞民,裴玉珍,等.1987.液位型和液压型体积式应变仪[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(1).北京:地震出版社.131—135.SU Kai-zhi,LIU Rui-min,PEI Yu-zhen,et al.1987.Hydraulic level type and hydraulic pressure type dilatometers[A].In:Institute of Crustal Dynamics of China Earthquake Administration(ed).Bulletin of the Institute ofCrustal Dynamics(1).Seismological Press,Beijing.131—135(in Chinese).
苏恺之.2003.地应变观测的物理解释-漂移、噪声和突跳[A].见:苏恺之等编.钻孔地应变观测新进展.北京:地震出版社.95—110.SU Kai-zhi.2003.Physical explanation of strain observation-shift,noise and pulsation[A].In:SU Kai-zhiet al.(eds).New developments in the observation with borehole strainmeters.Seismological Press,Beijing.95—110(in Chinese).
王仁,黄杰藩,孙荀英,等.1982.华北地震构造应力场的模拟[J].中国科学(B辑),4:337—344.WANG Ren,HUANG Jie-fan,SUNXun-ying,et al.1982.Simulation of the tectonic stress field over North China[J].Science in China(Ser B),4:337—344(in Chinese).
汪素云,陈培善.1980.中国及邻区现代构造应力场的数值模拟[J].地球物理学报,23(1):35—45.WANG Su-yun,CHEN Pei-shan.1980.A numerical simulation of the present tectonic stress field of China and its vic-inity[J].Acta Geophysica Sinica,23(1):35—45(in Chinese).
易志刚,邱泽华,宋茉.2006.首都圈地区数字化钻孔应变观测资料分析[J].大地测量与地球动力学,26(3):53—58.YI Zhi-gang,QIU Ze-hua,SONG Mo.2006.Analysis of digital recordings of borehole strainmeters in the Capital area[J].Journal of Geodesy and Geodynamics,26(3):53—58(in Chinese).
张东宁,高龙生.1989.东亚地区应力场的三维数值模拟[J].中国地震,5(4):24—33.ZHANG Dong-ning,GAO Long-sheng.1989.Three dimensional numerical simulation of eastern Asian stress field[J].Earthquake Research in China,5(4):24—33(in Chinese).
Hart R HG,Gladwin MT,Gwyther R L,et al.1996.Tidal calibration of borehole strain metrics:Removing the effectsof small-scale inhomogeneity[J].J Geophy Res,101(B11):25553—25571.
Hill D P,Reasonberg P A,Michael A,et al.1993.Seismicity remotely triggered by the magnitude7·3Landers,Cali-fornia earthquake[J].Science,260:1617—1623.
Ishii H,Yamauchi T,Matsumoto S,et al.2002.Development of multi-component borehole instrument for earthquakeprediction study:some observed examples of precursory and co-seismic phenomena relating to earthquake swarmsand application of the instrument for rock mechanics[A].In:Ogasawara Het al(eds).Seismic Process Monito-ring.Rotterdam:Balkema,365—377.
Linde A T,Gladwin MT,Johnston MJ S,et al.1996.A slowearthquake sequence near San Juan Bautista,Californiain December1992[J].Nature,383:65—69.
Massonnet D,Rossi M,Carmona C,et al.1993.The displacement field of the Landers earthquake mapped by radar in-terferometry[J].Nature,364:138—142.
Okada Y.1985.Surface deformation due to shear and tensile faults in a half-space[J].Bull Seism Soc Am,75:1135—1154.
Okada Y.1992.Internal deformation due to shear and tensile faults in a half-space[J].Bull Seis Soc Am,82:1018—1040.
Sacks I S,Suyehiro S,Evertson D W,et al.1971.Sacks-Evertson strainmeter,its installation in Japan and some pre-liminary results concerning strain steps[J].Pap Met Geophys,22:195—207.
Sacks I S,Suyehiro S,Linde A T,et al.1978.Slow earthquake and stress distribution[J].Nature,275:5681,599—602.
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