基于汶川地震同震地下水位变化反演含水层体应变
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摘要
许多地下流体监测井在地震发生时都能记录到同震水位变化,而利用地下水位的同震响应特征以及水位固体潮效应可以反演地震对含水层产生的体应变量.本文尝试从大尺度上对大地震引起的体应变变化进行研究,为此收集了位于我国大陆不同构造活动区5口地下流体监测井两年半的水位数据资料进行分析,去除干扰项,提取出水位固体潮成分,进行调和分析求取潮汐因子,并反演出汶川MS8.0地震对这5口井所在含水层产生的体应变量.结果显示,汶川大地震对这5口井-含水层造成的体应变量基本在10-7量级.地震引起的体应变随距离的衰减规律比较复杂,其不仅与震中距有关,而且与活动断裂带的展布和地壳岩体结构等密切相关.
Water level in many wells will change in response to an earthquake.One can use the coseismic water level change and its response to tide effect to calculate the volumetric strain in aquifer induced by the earthquake.We tried to study the changes in volumetric strain induced by great earthquakes in large scale.The two and a half years of original groundwater level data,recorded in the five wells located in different tectonic settings,were firstly corrected by removing both the trend and barometric pressure effect.Then harmonic analysis was used to calculate the tidal factor for each well-aquifer system,and further the volumetric strains of these five well-aquifer systems were calculated based on the tidal factors and groundwater level changes in response to the Wenchuan earthquake.The result shows that the volumetric strain in aquifers caused by the earthquake may reach 10-7.The attenuation of volumetric strain induced by the earthquake is complicated,and it may be determined by the distribution of active faults,structure of crustal media,as well as the earthquake epicentral distance.
Water level in many wells will change in response to an earthquake.One can use the coseismic water level change and its response to tide effect to calculate the volumetric strain in aquifer induced by the earthquake.We tried to study the changes in volumetric strain induced by great earthquakes in large scale.The two and a half years of original groundwater level data,recorded in the five wells located in different tectonic settings,were firstly corrected by removing both the trend and barometric pressure effect.Then harmonic analysis was used to calculate the tidal factor for each well-aquifer system,and further the volumetric strains of these five well-aquifer systems were calculated based on the tidal factors and groundwater level changes in response to the Wenchuan earthquake.The result shows that the volumetric strain in aquifers caused by the earthquake may reach 10-7.The attenuation of volumetric strain induced by the earthquake is complicated,and it may be determined by the distribution of active faults,structure of crustal media,as well as the earthquake epicentral distance.
引文
侯茂生.1984.苏10井水位与应力应变的关系[J].地震保护,6(1):90-97.
黄辅琼.2008.中国大陆地震地下水观测井网对远距离大地震的响应[D].北京:中国地震局地球物理研究所:79-80.
晏锐,高福旺,陈颙.2007.由井-含水层系统的水位动态反演含水层体应变[J].中国地震,23(3):303-309.
张昭栋,张广诚.1987.利用水位阶变资料反演震时应力的调整变化[J].地震研究,10(6):693-702.
张昭栋,刘庆国,耿杰.1999.由承压井水位动态反演水井含水层的应力变化[J].华南地震,19(1):37-42.
Bredehoeft J D.1967.Response of well-aquifer systems to earth tide[J].J Geophy Res,72(12):3075-3087.
Gahalaut K,Gahalaut V K,Chadha R K.2010.Analysis of coseismic water-level changes in the wells in the Koyna-War-na region,Western India[J].Bull Seism Soc Amer,100(3):1389-1394.
Igarashi G,Wakita H.1991.Tidal responses and earthquake-related changes in the water level of deep wells[J].J Geo-phy Res,96(B3):4269-4278.
Narasimhan T N,Kanehiro B Y.1984.Interpretation of earth tide response of three deep confined aquifers[J].J GeophyRes,89(B3):1913-1924.
Nathanial J T,Todd C R.2007.Removal of barometric press effects and earth tides from observed water levels[J].Ground Water,45(1):101-105.
Rhoads G H,Edwin S R.1979.Determination of aquifer parameters from well tides[J].J Geophy Res,84(B11):6071-6082.
Roeloff E.1996.Poroelastic techniques in the study of earthquake-related hydrologic phenomenon[J].Adv Geophy,37:135-195.
Samik S.2006.ResponseofAlaskanWelltoNearandDistantLargeEarthquakes[D].Fairbanks,Alaska:Universityof Alaska Fairbanks:8-11.
Tomo S,Norio M,Fujio A,Noritoshi O,Hiroaki T,Ryuji I.2010.Linear poroelasticity of groundwater levels from ob-servational records at wells in Hokkaido,Japan[J].Tectonophysics,483(3-4):305-309.
Tsutomu S,Norio M,Yuichi K,Naoji K,Makoto T,Yasuto K,Hisao I C,Takashi S,Kunio O,Shigeki T.2004.Changes in groundwater level associated with the2003Tokachi-oki earthquake[J].Earth Planets Space,56(3):395-400.
Wang H.2000.Theory of Liner Poroelasticity[M].Princeton:Princeton University Press:80-85.
Yuichi K,Naoji K,Makoto T,Norio M,Tsutomu S.2006.Changes in groundwater levels or pressures associated withthe2004earthquake off the west coast of northern Sumatra(M9.0)[J].Earth Planets Space,58(2):173-179.
黄辅琼.2008.中国大陆地震地下水观测井网对远距离大地震的响应[D].北京:中国地震局地球物理研究所:79-80.
晏锐,高福旺,陈颙.2007.由井-含水层系统的水位动态反演含水层体应变[J].中国地震,23(3):303-309.
张昭栋,张广诚.1987.利用水位阶变资料反演震时应力的调整变化[J].地震研究,10(6):693-702.
张昭栋,刘庆国,耿杰.1999.由承压井水位动态反演水井含水层的应力变化[J].华南地震,19(1):37-42.
Bredehoeft J D.1967.Response of well-aquifer systems to earth tide[J].J Geophy Res,72(12):3075-3087.
Gahalaut K,Gahalaut V K,Chadha R K.2010.Analysis of coseismic water-level changes in the wells in the Koyna-War-na region,Western India[J].Bull Seism Soc Amer,100(3):1389-1394.
Igarashi G,Wakita H.1991.Tidal responses and earthquake-related changes in the water level of deep wells[J].J Geo-phy Res,96(B3):4269-4278.
Narasimhan T N,Kanehiro B Y.1984.Interpretation of earth tide response of three deep confined aquifers[J].J GeophyRes,89(B3):1913-1924.
Nathanial J T,Todd C R.2007.Removal of barometric press effects and earth tides from observed water levels[J].Ground Water,45(1):101-105.
Rhoads G H,Edwin S R.1979.Determination of aquifer parameters from well tides[J].J Geophy Res,84(B11):6071-6082.
Roeloff E.1996.Poroelastic techniques in the study of earthquake-related hydrologic phenomenon[J].Adv Geophy,37:135-195.
Samik S.2006.ResponseofAlaskanWelltoNearandDistantLargeEarthquakes[D].Fairbanks,Alaska:Universityof Alaska Fairbanks:8-11.
Tomo S,Norio M,Fujio A,Noritoshi O,Hiroaki T,Ryuji I.2010.Linear poroelasticity of groundwater levels from ob-servational records at wells in Hokkaido,Japan[J].Tectonophysics,483(3-4):305-309.
Tsutomu S,Norio M,Yuichi K,Naoji K,Makoto T,Yasuto K,Hisao I C,Takashi S,Kunio O,Shigeki T.2004.Changes in groundwater level associated with the2003Tokachi-oki earthquake[J].Earth Planets Space,56(3):395-400.
Wang H.2000.Theory of Liner Poroelasticity[M].Princeton:Princeton University Press:80-85.
Yuichi K,Naoji K,Makoto T,Norio M,Tsutomu S.2006.Changes in groundwater levels or pressures associated withthe2004earthquake off the west coast of northern Sumatra(M9.0)[J].Earth Planets Space,58(2):173-179.
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