龙滩水库诱发地震的孔隙压力扩散特征
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摘要
利用孔隙压力扩散机制,分析了广西省龙滩水库与蓄水有关的小震精定位数据,获得了5个分区的流体孔隙压力扩散特征.龙滩水库与蓄水有关的小震活动表现出明显分区现象,使用多源孔隙压力扩散过程触发机理,计算出5个分区流体孔隙压扩散系数值为0.04～0.65 m~2/s.根据5个分区流体孔隙压力扩散程度,将这5区划分为Ⅰ、Ⅱ、Ⅲ三种类型,各类型的流体孔隙压扩散系数分别为0.45～0.65 m~2/s,0.25 m~2/s和0.04～0.08 m~2/s.断裂发育的区域内,地震分布范围较大,地震优势分布方向与断裂一致或相交,而断裂不发育的地块内,地震分布集中,无优势分布方向.各分区岩性的差异与流体孔隙压扩散系数的关系不显著.同时,各分区流体孔隙压力扩散的持续时间和最大扩散距离等均与孔隙压扩散系数的大小具有很好的相关性,第二次蓄水后库区发生的M_L4.2最大水库诱发地震位于流体孔隙压扩散系数最大的Ⅰ区.本项研究对分析解释水库诱发震地震机理,定量评价水库诱发地震的危险性具有一定的参考价值.
We analyzed the precisely relocated microseismic events sequences of Longtan reservoir in Guangxi province.By applying pore pressure diffusion mechanism we identified typical spatiotemporal characteristics of 5 microseismic events swarms.Microseismic events sequences of Longtan reservoir showed obvious partitions characteristics,which can be interpreted by multisources triggering the diffusion of pore pressure.By assuming that each swarm was triggered by its own pore pressure source,diffusivities with values between 0.04 m~2/s and 0.65 m~2/s were estimated.Based on the pore pressure diffusion characteristics of different microseismic swarms, the 5 swarms can be divided into 3 types,with diffusivities of 0.45～0.65m~2/s,0.25m~2/s,and 0.04～0.08m~2/s,respectively.The 3 types of blocks have obvious structure differences,which are closely related to diffusivity values.Areas with fault structure have larger earthquake distribution,and predominant directions of the earthquake distribution are consistent or intersect with fault lines,while in the area without fault structure,the earthquake distribution is concentrated,without a dominant distribution direction.However,the relationship of lithology of different types and diffusivities is not obvious.At the same time,pore pressure diffusive duration time and the maximum diffusive distance of different types are well correlated with the pore pressure diffusivity.The biggest triggered earthquake of M_L4.2 occurred in the block of typeⅠwhich has the biggest diffusivity.This research may be helpful to the study of the mechanism of reservoir induced earthquake,and to assess the risk of reservoir induced earthquake.
We analyzed the precisely relocated microseismic events sequences of Longtan reservoir in Guangxi province.By applying pore pressure diffusion mechanism we identified typical spatiotemporal characteristics of 5 microseismic events swarms.Microseismic events sequences of Longtan reservoir showed obvious partitions characteristics,which can be interpreted by multisources triggering the diffusion of pore pressure.By assuming that each swarm was triggered by its own pore pressure source,diffusivities with values between 0.04 m~2/s and 0.65 m~2/s were estimated.Based on the pore pressure diffusion characteristics of different microseismic swarms, the 5 swarms can be divided into 3 types,with diffusivities of 0.45～0.65m~2/s,0.25m~2/s,and 0.04～0.08m~2/s,respectively.The 3 types of blocks have obvious structure differences,which are closely related to diffusivity values.Areas with fault structure have larger earthquake distribution,and predominant directions of the earthquake distribution are consistent or intersect with fault lines,while in the area without fault structure,the earthquake distribution is concentrated,without a dominant distribution direction.However,the relationship of lithology of different types and diffusivities is not obvious.At the same time,pore pressure diffusive duration time and the maximum diffusive distance of different types are well correlated with the pore pressure diffusivity.The biggest triggered earthquake of M_L4.2 occurred in the block of typeⅠwhich has the biggest diffusivity.This research may be helpful to the study of the mechanism of reservoir induced earthquake,and to assess the risk of reservoir induced earthquake.
引文
[1]Masajiro Imoto.Point process modelling of reservoir induced seismicity.J.Appl.Probab,2001,38(2001):232-242.
[2]Baecher G B,Keeney R L.Statistical examination of reservoir-induced seismicity.Bulletin of the Seismological Society of America,1982,72(2):553--569
[3]Ramesh Chander.Can dams and reservoirs cause earthquakes? Resonance,1999,4(11):4-13
[4]Chen Linyue,Pradeep Talwani.Reservoir-induced seismicity in China.PureAppl.Geophys,1998,153(1):133-149
[5]Hu Yuliang,Liu Zuyuan,Yang Oingyuan,et al.Induced seismicity at Wujiangdu reservoir,China:a case induced in the Karst area.Pure and Applied Geophysics,1995,147(2): 409-418
[6]Shapiro S A,Audigane P,Royer J J.Large-scale in situ permeability tensor of rocks from induced microseismicity. Geophys.J.Internat.,1999,137(1):207-213
[7]Shapiro S A,Huenges E,Borm G.Estimating the crust permeability from fluid-injection induced seismic emission at the KTB site.Geophys.J.Internat.1997,131(2):15-18
[8]Shapiro S A,Royer J J,Audigane P.Reply to comment by F.H.Cornet on“large scale in situ permeability tensor of rocks from induced microseismicity”.Geophys.J.Internat, 2000,140(2):470-473
[9]Audigane P.Caracterisation microsismique des massifs rocheux fractures.Modelisation thermo-hydraulique.Application au concept geothermique de Soultz[Ph.D.thesis].France, Nancy:INPL,2000
[10]Pradeep Talwani,Steve Acree.Pore pressure diffusion and the mechanism of reservoir induced seismicity.Pure and Applied Geophysics,1984,122(6):947-965
[11]Talwani P.Seismogenic properties of the crust inferred from recent studies of reservoir-induced seismicity--Application to Koyna.Current Sci.,2000,79(9):1327-1333
[12]陈翰林,赵翠萍,修济刚等.龙滩水库地震精定位及活动特征研究.地球物理学报,2009,52(8):2035-2043 Chen H L,Zhao C P,Xiu J G,et al.Study on precise relocation of Longtan reservoir earthquakes and its seismic activity.Chinese J.Geophys.(in Chinese),2009,52(8):2035- 2043
[13]Parotidis M,Shapiro S A,Rothert E.Back front of seismicity induced after termination of borehole fluid injection.Geophys. Res.Lett.,2004,31(2),L02612,doi:10.1029/2003GL018987. http://userpage.fu -berlin.de/-seis/people / mparotid / ??publications/grl04a.pdf
[14]莫敬业.广西通志·地震志.南宁:广西人民出版社,1990. 32-80 Mo J Y.Annals of Guangxi Earthquake(in Chinese). Nanning:Guangxi People Press,1990.32-80
[15]郭培兰,姚宏,袁媛.龙滩水库地震危险性分析.高原地震,2006,18(4):17-23 Guo P L,Yao H,Yuan Y.Analysis on potential seismic risk in Longtan reservoir.Plateau Earthquake Research(in Chinese),2006,18(4):17-23
[16]汪素云,俞言祥.震级转换关系及其对地震活动性参数的影响研究.震灾防御技术,2009,4(2):141-149 Wang S Y,Yu Y X.Research on empirical relationship of earthquake magnitude scales and its influence on seismicity parameters.Technology for Earthquake Disaster Prevention (in Chinese),2009,4(2):141-149
[2]Baecher G B,Keeney R L.Statistical examination of reservoir-induced seismicity.Bulletin of the Seismological Society of America,1982,72(2):553--569
[3]Ramesh Chander.Can dams and reservoirs cause earthquakes? Resonance,1999,4(11):4-13
[4]Chen Linyue,Pradeep Talwani.Reservoir-induced seismicity in China.PureAppl.Geophys,1998,153(1):133-149
[5]Hu Yuliang,Liu Zuyuan,Yang Oingyuan,et al.Induced seismicity at Wujiangdu reservoir,China:a case induced in the Karst area.Pure and Applied Geophysics,1995,147(2): 409-418
[6]Shapiro S A,Audigane P,Royer J J.Large-scale in situ permeability tensor of rocks from induced microseismicity. Geophys.J.Internat.,1999,137(1):207-213
[7]Shapiro S A,Huenges E,Borm G.Estimating the crust permeability from fluid-injection induced seismic emission at the KTB site.Geophys.J.Internat.1997,131(2):15-18
[8]Shapiro S A,Royer J J,Audigane P.Reply to comment by F.H.Cornet on“large scale in situ permeability tensor of rocks from induced microseismicity”.Geophys.J.Internat, 2000,140(2):470-473
[9]Audigane P.Caracterisation microsismique des massifs rocheux fractures.Modelisation thermo-hydraulique.Application au concept geothermique de Soultz[Ph.D.thesis].France, Nancy:INPL,2000
[10]Pradeep Talwani,Steve Acree.Pore pressure diffusion and the mechanism of reservoir induced seismicity.Pure and Applied Geophysics,1984,122(6):947-965
[11]Talwani P.Seismogenic properties of the crust inferred from recent studies of reservoir-induced seismicity--Application to Koyna.Current Sci.,2000,79(9):1327-1333
[12]陈翰林,赵翠萍,修济刚等.龙滩水库地震精定位及活动特征研究.地球物理学报,2009,52(8):2035-2043 Chen H L,Zhao C P,Xiu J G,et al.Study on precise relocation of Longtan reservoir earthquakes and its seismic activity.Chinese J.Geophys.(in Chinese),2009,52(8):2035- 2043
[13]Parotidis M,Shapiro S A,Rothert E.Back front of seismicity induced after termination of borehole fluid injection.Geophys. Res.Lett.,2004,31(2),L02612,doi:10.1029/2003GL018987. http://userpage.fu -berlin.de/-seis/people / mparotid / ??publications/grl04a.pdf
[14]莫敬业.广西通志·地震志.南宁:广西人民出版社,1990. 32-80 Mo J Y.Annals of Guangxi Earthquake(in Chinese). Nanning:Guangxi People Press,1990.32-80
[15]郭培兰,姚宏,袁媛.龙滩水库地震危险性分析.高原地震,2006,18(4):17-23 Guo P L,Yao H,Yuan Y.Analysis on potential seismic risk in Longtan reservoir.Plateau Earthquake Research(in Chinese),2006,18(4):17-23
[16]汪素云,俞言祥.震级转换关系及其对地震活动性参数的影响研究.震灾防御技术,2009,4(2):141-149 Wang S Y,Yu Y X.Research on empirical relationship of earthquake magnitude scales and its influence on seismicity parameters.Technology for Earthquake Disaster Prevention (in Chinese),2009,4(2):141-149
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