四川省大凉山腹地当前地应力状态分析
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摘要
在四川省大凉山腹地深度分别为190.15 m和364.10 m的两个钻孔中进行水压致裂地应力测量,以获得当前浅部地壳应力的状态.测量结果表明,在测试段深度内,实测最大水平主应力最高值为14.68MPa,与该区域内已有近似深度地应力测量结果(20 MPa)相比,此次测值有所降低;3个主应力之间的关系为:最大水平主应力>最小水平主应力>垂直应力,表明大凉山地区地壳浅部构造应力场以水平应力为主导;最大水平主应力方向为北西至北西西向,与区域活动构造的性质和震源机制解得出的主压应力方向基本符合;最后,利用库伦摩擦滑动准则,讨论了当断层摩擦因数μ为0.6~1.0时,测区内主要断裂在该应力状态下的稳定性,认为测区内现今最大水平主应力值暂时没有达到使区域逆断层发生瞬间摩擦滑动的临界值.
By the hydro-fracturing method,in-situ stresses were measured in two drill holes at 190.15 m and 364.10 m to obtain the in-situ stress state of the shallow crust.The results indicate that the maximum value of the maximum horizontal principal stress is 14.68.MPa at the depths,which is lower than the previous measurement(20.MPa);The relation among the three principal stresses is the maximum horizontal principal stress﹥the minimum horizontal principal stress﹥the vertical stress,which reveals that the horizontal stress is larger than vertical static-rock pressure in the hinterland of Daliang Mountain;The direction of maximum principal tectonic stress is NW-NWW,which is in accordance with the implications from regional active faults and the direction of the principal compressive stress obtained by the focal mechanism solutions.Finally,Coulomb Friction criteria was used to investigate the stability of the active structure in the hinterland of Daliang Mountain,and μ(u is the friction coefficient) was 0.6～1.0.The results show that the maximum horizontal principal stress has not reached the critical value of momentarily sliping of reverse fault activity.
By the hydro-fracturing method,in-situ stresses were measured in two drill holes at 190.15 m and 364.10 m to obtain the in-situ stress state of the shallow crust.The results indicate that the maximum value of the maximum horizontal principal stress is 14.68.MPa at the depths,which is lower than the previous measurement(20.MPa);The relation among the three principal stresses is the maximum horizontal principal stress﹥the minimum horizontal principal stress﹥the vertical stress,which reveals that the horizontal stress is larger than vertical static-rock pressure in the hinterland of Daliang Mountain;The direction of maximum principal tectonic stress is NW-NWW,which is in accordance with the implications from regional active faults and the direction of the principal compressive stress obtained by the focal mechanism solutions.Finally,Coulomb Friction criteria was used to investigate the stability of the active structure in the hinterland of Daliang Mountain,and μ(u is the friction coefficient) was 0.6～1.0.The results show that the maximum horizontal principal stress has not reached the critical value of momentarily sliping of reverse fault activity.
引文
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[2]何宏林,池田安隆,何玉林,等.新生的大凉山断裂带-鲜水河-小江断裂系中段的截弯取直[J].中国科学:D辑,2008,38(5):564-574.
[3]陈长云,何宏林.大凉山地区新生代地壳缩短及其构造意义[J].地震地质,2008,30(2):443-453.
[4]唐荣昌,黄祖智,伍先国,等.则木河断裂全新世以来的新活动与地震[J].中国地震,1986,2(4):82-88.
[5]易桂喜,闻学泽,苏有锦.川滇活动地块东边界强震危险性研究[J].地球物理学报,2008,51(6):1719-1725.
[6]杜平山.则木河断裂带的走滑位移及滑动速率[J].四川地震,2000,1(2):49-64.
[7]申旭辉,陈正位,许任德,等.凉山活动构造带晚新生代变形特征与位移规模[J].地震地质,2000,22(3):232-238.
[8]周荣军,黎小刚,黄祖智,等.四川大凉山断裂带的晚第四纪平均滑动速率[J].地震研究,2003,26(2):191-196.
[9]丁立丰,安其美,王海忠,等.金沙江溪洛渡水电站水压致裂地应力测量分析研究[J].中国地震,2004,20(1):95-100.
[10]FAIRHUSTC.Measurement of in-situ rock stresses,with piarticular veference to hydraulic fracturing[J].Hydro-fracturing,Rock Mesh and Engineering Geol,1967,2:12-19.
[11]蔡美峰.地应力测量原理和技术[M].北京:科技出版社,2006.
[12]吴忠,庞俊勇.煤矿地应力测量研究分析[J].焦作矿业学院学报,1993,22(2):62-68.
[13]李方全,孙世宗,李立球.华北及郯庐断裂带地应力测量[J].岩石力学与工程学报,1982,1(2):73-86.
[14]谢富仁,崔效峰,赵建涛,等.中国大陆邻区现代构造应力场分区[J].地球物理学报,2004,47(4):654-663.
[15]ZOBACK M D,HEALY J H.In-situ stress measurements to 3.5 km depth in the Cajon.Pass Scientific ResearchBore-hole:implications for the mechanics of crustal faulting[J].J.G.R,1992,97(B4):5039-5057.
[16]ZOBACK M D,HEOLY J H.Friction,faulting and in-situ stress[J].Annales Geophysics,1984,2(6):689-698.
[17]BYERLEE J O.Friction of rocks[J].Pageoph,1978,116(4/5):615-626.
[18]张伯崇,苏恺之.长江三峡坝区地壳应力与孔隙压力综合研究[M].北京:地震出版社,1996.
[19]丁建民.地壳构造与地壳应力[M].北京:地震出版社,1988.
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