三峡水库蓄水后等效应力场的数值模拟和胡家坪M_S4.1地震的孕震机理
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摘要
利用有限元方法,在三峡水库172m试验性蓄水后发生胡家坪MS4.1地震的大背景中,建立了三峡库首区三维线弹性有限元模型。计算得到了172m水位相对于蓄水前库首区地壳8km深度处的等效应力场,与该地区同期流动重力场异常分布特征基本一致。在此基础上,将蓄水后等效应力场的变化与胡家坪MS4.1地震对比后发现,本次地震发生在等效应力递增区与递减区的梯度带上。分析认为,这样的地段等效应力变化明显,是应力应变积累和构造活动强烈的部位,加之处于仙女山断裂的北端段,容易促使断裂失稳错动而引发地震活动。
Using finite element method,we established a 3D linear elastic finite element model of the head area of the Three Gorges Reservoir after the Hujiaping MS4.1 earthquake occurred after the 172 m level experimental impoundment.Then we calculated and obtained the equivalent stress field under 172 m water level and that in 8 km depth in the head area of the Three Gorges before impoundment,which are consistent with the distribution characteristics of contemporaneous flowing gravity field abnormality in this area.On this basis,we compared the equivalent stress field changes after the impoundment with the Hujiaping MS4.1 earthquake,and found that this earthquake occurred in the gradient zone between the increasing zone and decreasing zone of the equivalent stress.We analyzed that the equivalent stress varied distinctly in the gradient zone,where the stress and strain was accumulated and tectonic activity was intense.In addition,the gradient zone is located in the north section of the Xiannushan Fault,which is easy to make fault instable and move to induce the seismic activity.
Using finite element method,we established a 3D linear elastic finite element model of the head area of the Three Gorges Reservoir after the Hujiaping MS4.1 earthquake occurred after the 172 m level experimental impoundment.Then we calculated and obtained the equivalent stress field under 172 m water level and that in 8 km depth in the head area of the Three Gorges before impoundment,which are consistent with the distribution characteristics of contemporaneous flowing gravity field abnormality in this area.On this basis,we compared the equivalent stress field changes after the impoundment with the Hujiaping MS4.1 earthquake,and found that this earthquake occurred in the gradient zone between the increasing zone and decreasing zone of the equivalent stress.We analyzed that the equivalent stress varied distinctly in the gradient zone,where the stress and strain was accumulated and tectonic activity was intense.In addition,the gradient zone is located in the north section of the Xiannushan Fault,which is easy to make fault instable and move to induce the seismic activity.
引文
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张林洪,刘荣佩,周建芬,等.2002.构造型水库地震的断裂力学分析[J].地震研究,25(2):186-191.
张林洪,刘荣佩,周建芬,等.2004.库水压力作用下不同类型断层诱发水库地震的可能性分析[J].地震研究,27(3):241-245.
朱守彪,张培震.2009.2008年汶川MS8.0地震发生过程的动力学机制研究[J].地球物理学报,52(2):418-427.
Wang Q,Zhang P Z,Freumueller J T,et al.2001.Present-day crustal deformation in China constrained by global positional system meas-urements[J].Science,294(5542):574-577.
车用太,刘五洲.1998.地壳流体与地震活动关系及其在强震预测中的意义[J].地震地质,20(4):431-437.
陈明祥.2007.弹塑性力学[M].北京:科学出版社.
陈蜀俊,姚运生,蔡永建.2006.三峡库首区重点断裂围限区蓄水的加卸载效应[J].大地测量与地球动力学,26(4):97-101.
陈蜀俊,姚运生,曾佐勋,等.2005.三峡库首区蓄水前后构造应力场三维数值模拟研究[J].岩石力学与工程学报,4(2):5612-5617.
陈蜀俊.2005.三峡库首区蓄水前后构造应力场数值模拟及地震危险性研究[D].武汉:中国地质大学.
廖武林,张丽芬,姚运生.2009.三峡水库地震活动特征研究[J].地震地质,31(4):707-714.
田宗伟.2008.中国地震局地震研究所水库诱发地震研究室王秋良博士:秭归县4.1级地震属三峡地区正常背景条件下发生的构造地震[J].中国三峡建设(科技版),(1):56-63.
王博,刘耀伟,孙小龙.2008.地下流体与断裂活动关系的研究综述[J].地震研究,31(3):296-302.
吴建超,陈蜀俊,陈俊华.2009.三峡水库蓄水后全位移场变化的数值模拟[J].大地测量与地球动力学,29(6):52-55.
吴建超.2010.三峡库首区三维数值模拟及地震危险性研究[D].武汉:中国地震局地震研究所.
张林洪,刘荣佩,周建芬,等.2002.构造型水库地震的断裂力学分析[J].地震研究,25(2):186-191.
张林洪,刘荣佩,周建芬,等.2004.库水压力作用下不同类型断层诱发水库地震的可能性分析[J].地震研究,27(3):241-245.
朱守彪,张培震.2009.2008年汶川MS8.0地震发生过程的动力学机制研究[J].地球物理学报,52(2):418-427.
Wang Q,Zhang P Z,Freumueller J T,et al.2001.Present-day crustal deformation in China constrained by global positional system meas-urements[J].Science,294(5542):574-577.
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