华北强震前地下流体长趋势变化特征及其产生机理的研究
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摘要
分析了华北地区自1976年以来MS≥6.0地震前地下流体长趋势变化的形态、演化特征。结果表明:地下流体长趋势变化出现时间早、范围广,具有协调性、重复性、迁移性等特性,主要沿构造带迁移,迁移方向为外围向内迁移或内部向外迁移;形态主要为趋势转折、破年变、加速等,其中绝对大多数为趋势转折变化;地下水位分析表明长趋势变化绝大部分呈现为缓慢上升或下降减缓的走势。对比研究了地壳形变与地下流体长趋势变化,发现地壳形变长趋势时间早于地下流体;形变出现张压变化与水位变化有比较密切的关系,即形变绝大部分出现缓慢压性变化或张性减缓变化,水位绝大部分出现缓慢上升或下降减缓变化。最后讨论了强震前地下流体长趋势变化产生的机理:在地震孕育过程初(早)期,构造应力的缓慢增强将使岩体所含裂缝闭合,地壳发生变形,从而改变岩体的空隙率及相应的孔隙压力和渗透率,引起诸如地下流体长趋势动态异常变化;构造应力缓慢增强并向未来震中聚集,造成地下流体长趋势动态异常变化向震中迁移;而深部物质的不断上涌和影响范围增大致使地下流体长趋势动态异常变化向外围迁移。
The long-time trend change shape and evolutionary characteristics of subsurface fluid in North China before MS≥6.0 earthquakes since 1976 are analysed.The results show that the begin time of long-time trend change of subsurface fluid is earlier,and the range is wider,with the characteristics of compatibility,repetition and migration etc.The migrate direction along major tectonic belt is from wide outer regions to epicenter area,or from epicenter area to wide outer region.The shape of changes show trend turn change,damage annual variation and accelerating variation etc,among them the trend turn change is majority shape.Study on level of underground water shows that the majority variation shapes of long-time trend change on level of underground water are slow elevation or descending diminution.Then long-time trend change of subsurface fluid and crustal deformation before strong earthquakes are comparatively studied.The results discover that the begin time of crustal deformation is earlier than it of subsurface fluid,the tensor-pressure variation of crustal deformation is more closely related with the level variation of underground water,namely if change of crustal deformation shows mostly slow pressure or tensor diminution,the change of underground water level shows slow elevation or descending diminution.Finally,the mechanism on long-time trend change of subsurface fluid before strong earthquake is discussed.Slow incremental tectonic stress make crack of rock closure and crust deform,the crust deformation changes porosity,pore pressure and permeability,causes the long-time trend abnormal change of subsurface fluid in the early stage of preparation earthquake.The tectonic stress slowly enhancing and congregating to future seismic center cause the change to migrate into future seismic center.The continuously upwelling of deep material and increment influencing range make the change migrate from future seismic center to outlying zone.
The long-time trend change shape and evolutionary characteristics of subsurface fluid in North China before MS≥6.0 earthquakes since 1976 are analysed.The results show that the begin time of long-time trend change of subsurface fluid is earlier,and the range is wider,with the characteristics of compatibility,repetition and migration etc.The migrate direction along major tectonic belt is from wide outer regions to epicenter area,or from epicenter area to wide outer region.The shape of changes show trend turn change,damage annual variation and accelerating variation etc,among them the trend turn change is majority shape.Study on level of underground water shows that the majority variation shapes of long-time trend change on level of underground water are slow elevation or descending diminution.Then long-time trend change of subsurface fluid and crustal deformation before strong earthquakes are comparatively studied.The results discover that the begin time of crustal deformation is earlier than it of subsurface fluid,the tensor-pressure variation of crustal deformation is more closely related with the level variation of underground water,namely if change of crustal deformation shows mostly slow pressure or tensor diminution,the change of underground water level shows slow elevation or descending diminution.Finally,the mechanism on long-time trend change of subsurface fluid before strong earthquake is discussed.Slow incremental tectonic stress make crack of rock closure and crust deform,the crust deformation changes porosity,pore pressure and permeability,causes the long-time trend abnormal change of subsurface fluid in the early stage of preparation earthquake.The tectonic stress slowly enhancing and congregating to future seismic center cause the change to migrate into future seismic center.The continuously upwelling of deep material and increment influencing range make the change migrate from future seismic center to outlying zone.
引文
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[23]Domenico P A.Transport phenomena in chemical rate processes in sediments[J].Annual Revirws of Earth and Planetary Sci-ences,1977,5:287-317.
[24]John D,Denis L.Mass and Energy Transport in a Deforming Earth's Crust,The Role of Fluids in Crustal Processes[M].Washing ton:National Academy Press,1990:27-41.
[2]国家地震局预测预防司.地下流体地震预报方法[M].北京:地震出版社,1997.
[3]车用太,鱼金子,刘五洲.水氡异常的水动力学机制[J].地震地质,1997,19(4):353-357.
[4]邵永新,李君英,李一兵,等.地下流体动态异常分布与构造的关系[J].西北地震学报,2000,22(3):284-287.
[5]刘耀炜,施锦.强震地下流体前兆信息特征[J].地震学报,2000,22(1):59-64.
[6]邵永新,李君英,田山,等.唐山7.8级地震前后地下流体动态异常演化特征[J].西北地震学报,2001,23(1):26-29.
[7]黄辅琼,邓志辉,顾瑾平,等.张北地震地下流体异常场的研究[J].地震,2002,22(4):114-122.
[8]张立,唐采,王世芹,等.宁蒗6.2姚安6.5和永胜6.0级地震前地下流体的短期变化[J].地震研究,2003,26(1):149-156.
[9]陆明勇,黄辅琼,刘善华,等.地壳变形与地下水相互作用及其异常关系初探[J].地震,2005,25(1):67-73.
[10]车用太,刘五洲.板内强震的中地壳硬夹层孕震与流体促震假设[J].地震学报,2000,22(1):93-101.
[11]陆明勇,牛安福,鲁德顺,等.地壳形变与地下水动态异常特征研究进展[J].西北地震学报,2005,27(1):89-95.
[12]陆明勇.地壳形变与地下水相互作用及“双力源”前兆观点[J].大地测量与地球动力学,2006,26(1):76-83.
[13]陆明勇.“双力源”地震前兆观点的进一步探讨[J].大地测量与地球动力学,2007,27(4):105-111.
[14]国家地震局一九七六年唐山地震编辑组.一九七六年唐山地震[M].北京:地震出版社,1982.
[15]徐常芳.壳内流体演化及地震成因(三)[J].地震学报,1997,19(2):139-144.
[16]张永仙.热应力三维数值模拟研究及热物质的运移在地震孕育过程中的作用探讨[D].北京:中国地震局地球物理研究所,1999.
[17]陈颙.地壳岩石的力学性能-理论基础与实验方法[M].北京:地震出版社,1988:30.
[18]Biot MA.Theory of elasticity and consolidation for a porous ani-sotropic solid[J].Journal of Applied Physics,1955,26:182-185.
[19]Biot MA.Thermoelasticity and irreversible thermodynamics[J].Journal of Applied Physics,1956,27:240-253.
[20]Nur A,Byerlee J D.An exact effective stress law for elastic de-formation of rocks with fluids[J].Journal of Geophysical Re-search,1971,76:6414-6419.
[21]Palciauskas VV,Domenico P A.Characterization of drained and undrained response of thermally loaded repository rocks[J].Wa-ter Resources Research,1982,18:281-290.
[22]Palciauskas V V,Domenico P A.Microfracture development in compacting sediments:Relations to hydrocarbon-maturation ki-netics[J].American Association of Petroleum Geologists Bulle-tin,1980,64:927-937.
[23]Domenico P A.Transport phenomena in chemical rate processes in sediments[J].Annual Revirws of Earth and Planetary Sci-ences,1977,5:287-317.
[24]John D,Denis L.Mass and Energy Transport in a Deforming Earth's Crust,The Role of Fluids in Crustal Processes[M].Washing ton:National Academy Press,1990:27-41.
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