隐伏逆断层破裂扩展特征的实验研究及其地震地质意义
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摘要
通过模拟实验研究了逆断层活动过程中上覆沉积层的破裂扩展特征,采用投影条纹测试方法分析了沉积层表面离面(即垂直)位移场的演化过程。结果表明,在沉积层厚度和断层倾角一定的条件下,基岩中的逆断层逐渐向上扩展,并在沉积层表面围绕基岩断层上断点的投影线形成一个离面位移梯度带(即形变带),基岩断层的位移越大,沉积层中的形变带越宽、变形越强烈;但当断层扩展至沉积层表面后,形变带宽度将保持稳定,只是变形随断层位移增加而更集中。对于同样的基岩断层位移和断层倾角,沉积层厚度越大,受基岩断层控制的形变带越宽,即基岩断层的影响范围越大;当沉积层厚度超过某一临界值时,沉积层中会发育因隆起引起的表面拉张破裂。在沉积层厚度和基岩断层位移量一定的情况下,基岩断层倾角的增加将会使表面形变带的宽度减小,但会使变形破坏程度更强烈。实验结果意味着,临界断层位移、临界沉积层厚度以及断层倾角对于确定隐伏逆断层发震产生的地表变形和破坏特征具有重要意义。文中的研究结果有助于进一步认识汶川MS8.0地震的地表变形特征。
In this paper,the rupture propagation along reverse fault in bedrock towards the overlying sediment layer has been studied using modeling tests and the evolution of the vertical displacement field on the surface of sediment layer has been measured using fringe projection technique,in which the effects of fault displacement,thickness of sediment layer and fault dip have been analyzed.The research results indicate that fault in bedrocks propagates gradually towards the overlying sediment layer and a gradient zone of vertical displacement(i.e.a deformation zone)surrounding the projection line of the upper end of fault in bedrock is formed on the surface of sediment layer as the fault slips,given a constant thickness of sediment layer and a constant fault dip.The larger the fault displacement is,the larger the width of the deformation zone and the deformation intensity are.However,the width of deformation zone keeps constant and only the deformation becomes more concentrated as fault displacement increases after the fault propagates to the surface of sediment layer.Under the same fault displacement and the same fault dip,the thicker the sediment layer is,the wider the deformation zone controlled by the fault in bedrock is,i.e.the larger the influencing extent of the fault is.When the thickness of sediment layer exceeds a critical thickness,an extensional rupture may occur on the surface of the sediment layer caused by uplifting of the sediment layer.Under the same thickness of sediment layer and the same fault displacement,the width of the deformation zone on the surface of sediment layer decreases but the deformation intensity increases as fault dip increases.The experiment results imply that the critical fault displacement,the critical thickness of sediment layer and the fault dip play important roles in determining the surface deformation and rupture of earthquake generated by buried reverse fault.The results obtained in this paper are valuable for further understanding the characteristics of surface deformation caused by Wenchuan earthquake.
In this paper,the rupture propagation along reverse fault in bedrock towards the overlying sediment layer has been studied using modeling tests and the evolution of the vertical displacement field on the surface of sediment layer has been measured using fringe projection technique,in which the effects of fault displacement,thickness of sediment layer and fault dip have been analyzed.The research results indicate that fault in bedrocks propagates gradually towards the overlying sediment layer and a gradient zone of vertical displacement(i.e.a deformation zone)surrounding the projection line of the upper end of fault in bedrock is formed on the surface of sediment layer as the fault slips,given a constant thickness of sediment layer and a constant fault dip.The larger the fault displacement is,the larger the width of the deformation zone and the deformation intensity are.However,the width of deformation zone keeps constant and only the deformation becomes more concentrated as fault displacement increases after the fault propagates to the surface of sediment layer.Under the same fault displacement and the same fault dip,the thicker the sediment layer is,the wider the deformation zone controlled by the fault in bedrock is,i.e.the larger the influencing extent of the fault is.When the thickness of sediment layer exceeds a critical thickness,an extensional rupture may occur on the surface of the sediment layer caused by uplifting of the sediment layer.Under the same thickness of sediment layer and the same fault displacement,the width of the deformation zone on the surface of sediment layer decreases but the deformation intensity increases as fault dip increases.The experiment results imply that the critical fault displacement,the critical thickness of sediment layer and the fault dip play important roles in determining the surface deformation and rupture of earthquake generated by buried reverse fault.The results obtained in this paper are valuable for further understanding the characteristics of surface deformation caused by Wenchuan earthquake.
引文
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刘学增,滨田政则.2004.活断层破坏在土体中传播的实验研究[J].岩土工程学报,26(3):425—427.LIUXue-zeng,Hamada M.2004.Experiments on rupture propagation of active faults in soil[J].Chinese Journal ofGeotechnical Engineering,26(3):425—427.
马少鹏,金观昌,代树红.2002.应用时域相位解包方法的三维形貌测量系统[J].光学技术,28(5):395—397.MA Shao-peng,JIN Guan-chang,DAI Shu-hong.2002.3D profilometry system based on temporal phase unwrappingmethod[J].Optical Technique,28(5):395—397.
冉勇康,陈立春,沈军,等.2007.乌鲁木齐西山断裂组与地表破裂型逆断层古地震识别标志[J].地震地质,29(2):218—234.RAN Yong-kang,CHEN Li-chun,SHEN Jun,et al.2007.Xishan Fault group near Urumqi City and paleoearthquake i-dentification on reverse fault[J].Seismology and Geology,29(2):218—234(in Chinese).
屈春燕,宋小刚,张桂芳,等.2008.汶川MS8.0地震InSAR同震形变场特征分析[J].地震地质,30(4):1076—1084.QU Chun-yan,SONG Xiao-gang,ZHANG Gui-fang,et al.2008.Analysis on the characteristics of InSAR coseismic de-formation of theMS8.0Wenchuan earthquake[J].Seismology and Geology,30(4):1076—1084.
孙建宝,梁芳,沈正康,等.2008.汶川MS8.0地震InSAR形变观测及初步分析[J].地震地质,30(3):789—795.SUN Jian-bao,LIANG Fang,SHEN Zheng-kang,et al.2008.InSAR deformation observation and preliminary analysisof theMS8.0Wenchuan earthquake[J].Seismology and Geology,30(3):789—795(in Chinese).
徐锡伟,于贵华,马文涛,等.2002.活断层地震地表破裂“避让带”宽度确定的依据与方法[J].地震地质,24(4):470—483.XUXi-wei,YUGui-hua,MAWen-tao,et al.2002.Evidence and methods for determining the safety distance fromthe poten-tial earthquake surface rupture on active fault[J].Seismology and Geology,24(4):470—483(in Chinese).
徐锡伟,闻学泽,叶建青,等.2008.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,30(3):597—629.XU Xi-wei,WEN Xue-ze,YE Jian-qing,et al.2008.TheMS8.0Wechuan earthquake surface ruptures and its seis-mogenic structure[J].Seismology and Geology,30(3):597—629(in Chinese).
赵雷,李小军,霍达.2007.断层错动引发基岩上覆土层破裂问题[J].北京工业大学学报,33(1):20—25.ZHAO Lei,LI Xiao-jun,HUO Da.2007.Problems of rupturing process of overlaying soil due to fault dislocation ofbedrock[J].Journal of Beijing University of Technology,33(1):20—25(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,51(4):1066—1073.ZHANG Pei-zhen,XUXi-wei,WENXue-ze,et al.2008.Slip rates and recurrence intervals of Longmenshan active faultzone and tectonic implications for mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese J Geophys,51(4):1066—1073(in Chinese).
Bary J D,Seed R B.1994.Earthquake fault rupture propagation through soil[J].Journal of Geotechnical Engineer-ing,120(3):543—561.
Dolan J F,Pratt TL.1997.High-resolution seismic reflection profiling of the Santa Monica Fault zone,West Los An-geles,California[J].Geophy Res Lett,24(16):2052—2054.
Taniyama H,Watanabe H.2000.Deformation of sandy deposits by fault movement[A].In:Proc.12th WCEE2000,Tokyo:McGraw Hill,1—6.
Viola G,Odonne F,MancktelowNS.2004.Analogue modeling of reverse fault reactivation in strike-slip and transpres-sive regimes:application to the Giudicarie Fault system,Italian Eastern Alps[J].Journal of Structural Geology,36:401—418.
邓起东.2002.城市活动断裂探测和地震危险性评价问题[J].地震地质,24(4):601—605.DENG Qi-dong.2002.Exploration and seismic hazard assessments of active faults in urban areas[J].Seismology andGeology,24(4):601—605(in Chinese).
董津城.1999.发震断裂的安全距离规定简介[J].工程抗震,(2):14—16.DONG Jin-cheng.1999.Brief introduction to the stipulations on safety distance from earthquake causative fault[J].Earthquake Resistant Engineering,(2):14—16(in Chinese).
郭恩栋,冯启民,薄景山,等.2001.覆盖土层场地地震断裂实验[J].地震工程与工程振动,21(3):145—149.GUO En-dong,FENG Qi-min,BO Jing-shan,et al.2001.Seismic test of soil site rupture under fault displacements[J].Journal of Earthquake Engineering and Engineering Vibration,21(3):145—149(in Chinese).
韩竹军,冉勇康,徐锡伟.2002.隐伏活断层未来地表破裂带宽度与位错量初步研究[J].地震地质,24(4):484—494.HAN Zhu-jun,RAN Yong-kang,XU Xi-wei.2002.Primary study on possible width and displacement of future surfacerupture zone produced by buried active fault[J].Seismology and Geology,24(4):484—494(in Chinese).
李锡堤,郑锦桐,廖启雯.2000.921集集大地震的地盘变形现象及断层禁限建问题[A].见:第八届台湾地区地球物理研讨会论文集.669—675.Lee C T,Cheng C T,Liao C W.2000.Ground deformation of the Chi-Chi earthquake and problems of no or limitedconstruction on active faults[A].In:Collection Papers of the8th Taiwan Geophysics Meeting,Taibei,669—675.
刘学增,滨田政则.2004.活断层破坏在土体中传播的实验研究[J].岩土工程学报,26(3):425—427.LIUXue-zeng,Hamada M.2004.Experiments on rupture propagation of active faults in soil[J].Chinese Journal ofGeotechnical Engineering,26(3):425—427.
马少鹏,金观昌,代树红.2002.应用时域相位解包方法的三维形貌测量系统[J].光学技术,28(5):395—397.MA Shao-peng,JIN Guan-chang,DAI Shu-hong.2002.3D profilometry system based on temporal phase unwrappingmethod[J].Optical Technique,28(5):395—397.
冉勇康,陈立春,沈军,等.2007.乌鲁木齐西山断裂组与地表破裂型逆断层古地震识别标志[J].地震地质,29(2):218—234.RAN Yong-kang,CHEN Li-chun,SHEN Jun,et al.2007.Xishan Fault group near Urumqi City and paleoearthquake i-dentification on reverse fault[J].Seismology and Geology,29(2):218—234(in Chinese).
屈春燕,宋小刚,张桂芳,等.2008.汶川MS8.0地震InSAR同震形变场特征分析[J].地震地质,30(4):1076—1084.QU Chun-yan,SONG Xiao-gang,ZHANG Gui-fang,et al.2008.Analysis on the characteristics of InSAR coseismic de-formation of theMS8.0Wenchuan earthquake[J].Seismology and Geology,30(4):1076—1084.
孙建宝,梁芳,沈正康,等.2008.汶川MS8.0地震InSAR形变观测及初步分析[J].地震地质,30(3):789—795.SUN Jian-bao,LIANG Fang,SHEN Zheng-kang,et al.2008.InSAR deformation observation and preliminary analysisof theMS8.0Wenchuan earthquake[J].Seismology and Geology,30(3):789—795(in Chinese).
徐锡伟,于贵华,马文涛,等.2002.活断层地震地表破裂“避让带”宽度确定的依据与方法[J].地震地质,24(4):470—483.XUXi-wei,YUGui-hua,MAWen-tao,et al.2002.Evidence and methods for determining the safety distance fromthe poten-tial earthquake surface rupture on active fault[J].Seismology and Geology,24(4):470—483(in Chinese).
徐锡伟,闻学泽,叶建青,等.2008.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,30(3):597—629.XU Xi-wei,WEN Xue-ze,YE Jian-qing,et al.2008.TheMS8.0Wechuan earthquake surface ruptures and its seis-mogenic structure[J].Seismology and Geology,30(3):597—629(in Chinese).
赵雷,李小军,霍达.2007.断层错动引发基岩上覆土层破裂问题[J].北京工业大学学报,33(1):20—25.ZHAO Lei,LI Xiao-jun,HUO Da.2007.Problems of rupturing process of overlaying soil due to fault dislocation ofbedrock[J].Journal of Beijing University of Technology,33(1):20—25(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,51(4):1066—1073.ZHANG Pei-zhen,XUXi-wei,WENXue-ze,et al.2008.Slip rates and recurrence intervals of Longmenshan active faultzone and tectonic implications for mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese J Geophys,51(4):1066—1073(in Chinese).
Bary J D,Seed R B.1994.Earthquake fault rupture propagation through soil[J].Journal of Geotechnical Engineer-ing,120(3):543—561.
Dolan J F,Pratt TL.1997.High-resolution seismic reflection profiling of the Santa Monica Fault zone,West Los An-geles,California[J].Geophy Res Lett,24(16):2052—2054.
Taniyama H,Watanabe H.2000.Deformation of sandy deposits by fault movement[A].In:Proc.12th WCEE2000,Tokyo:McGraw Hill,1—6.
Viola G,Odonne F,MancktelowNS.2004.Analogue modeling of reverse fault reactivation in strike-slip and transpres-sive regimes:application to the Giudicarie Fault system,Italian Eastern Alps[J].Journal of Structural Geology,36:401—418.
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