动态应力作用与地震机制的初步研究
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摘要
运用三维非线性动态有限元计算仿真方法研究了动态应力的作用及其与地震机制的关系.结果表明地震产生的冲击力在加载与卸载过程中形成的应力波,在遇断层时多次反射并发生半波损失,反射的应力波叠加或干涉而形成的动态应力使围压减小和波动.地震动态应力使围压产生低值波动,一方面使围压减小、摩擦力减小;另一方面,使裂纹串通、介质松动、接触面变平,降低摩擦系数、减小剪切强度.由此均导致抗剪强度降低,从而触发地震.动态应力作用时间短,触发地震大小与动态应力大小成正比、与距离成反比,触发地震位置、过程与孕震体断层产状有关.
We use the three-dimensional nonlinear finite element method to perform a modeling study on effects of dynamical stress and its relation to earthquake mechanism. The result shows that stress wave is generated by the shock force of earthquakes during processes of loading and unloading. When this wave encounters a fault, it is reflected many times, causing half-wavelength loss. The dynamical stress produced by superposition or interference of reflected stress wave makes confining pressure reduce and change at low values. On the one hand, the declined confining pressure reduces friction on the fault surface. On the other hand, the changing confining pressure brings about crack linkage, medium loosing, contact interface flattening, friction coefficient dropping, and shear strength reducing. These effects can trigger earthquakes. The affecting time of the dynamic stress is short. The magnitude of the event triggered by this stress is proportional to the size of the stress and inversely proportional to the distance. And the location and processes of the triggered earthquake are associated with the occurrence of the causative fault.
We use the three-dimensional nonlinear finite element method to perform a modeling study on effects of dynamical stress and its relation to earthquake mechanism. The result shows that stress wave is generated by the shock force of earthquakes during processes of loading and unloading. When this wave encounters a fault, it is reflected many times, causing half-wavelength loss. The dynamical stress produced by superposition or interference of reflected stress wave makes confining pressure reduce and change at low values. On the one hand, the declined confining pressure reduces friction on the fault surface. On the other hand, the changing confining pressure brings about crack linkage, medium loosing, contact interface flattening, friction coefficient dropping, and shear strength reducing. These effects can trigger earthquakes. The affecting time of the dynamic stress is short. The magnitude of the event triggered by this stress is proportional to the size of the stress and inversely proportional to the distance. And the location and processes of the triggered earthquake are associated with the occurrence of the causative fault.
引文
[1]Harris R A,Simpson R W.Suppression of large earthquake bystress shadows:Acomparison of Coulomb andrate-and-state.J.Geophys.Res.,1998,103:24439~24451
[2]沈正康,万永革,甘卫军等.东昆仑活动断裂带大地震之间的黏弹性应力触发研究.地球物理学报,2003,46(6):786~795Shen Z K,Wan YG,Gan WJ,et al.Viscoelastic triggering among large earthquakes along the east Kunlun fault system.Chinese J.Geophys.(in Chinese),2003,46(6):786~795
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[4]Pollitz F F,Sacks I S.The1995Kobe,Japan earthquake:a long-delayed aftershock of the offshore1994Tonankai and1946Nankaido earthquakes.Bull.Seism.Soc.Am.,1997,87:1~10
[5]Mohamad R,Darkal A N,Seber D,et al.Remote earthquake triggering alongthe Dead Seafault in Syriafollowingthe1995Gulf of Aqaba earthquake(Ms=7·3).Seismol.Res.Lett.,2000,71:47~52
[6]Cotton F,Coutant O.Dynamic stress variations due to shear faultsin a plane-layered medium.Geophys.J.Int.,1997,128:676~688
[7]Kilb D,Gomberg J,Bodin P.Earthquake triggering by dynamic stresses.Nature,2000,408:570~574
[8]Rigobert T,Douglas A W,Hiroshi I.Remote triggering of deep earthquakes in the2002Tonga sequences.Nature,2003,424(6951):921~925
[9]Byerlee J.Model for episodic flow of high pressure water in fault zones before earthquakes.Geology,1993,21:303~306
[10]Gomberg J.The failure of earthquake failure models.J.Geophys.Res.,2001,106(B8):16253~16263
[11]Sturtevant B,Kanamori H,Brodsky E E.Seismic triggering by rectified diffusionin geothermal systems.J.Geophys.Res.,1996,101:25269~25282
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[13]陆明勇,郑文衡.地壳块体动应力演化特征及其与地震关系的初步研究.地震学报,2005,27(3):282~291Lu MY,Zheng WH.Preliminary study on variation characteristics of ocean tide dynamic stress in crust and its relationship with earthquakes.Acta Seismologia Sinica,2005,18(3):303~312
[14]郑文衡,陆明勇.地震动态触发机制的初步研究.地球物理学报,2005,48(1):116~123Zheng WH,Lu MY.Apreliminary study on mechanismof dynamic triggering of earthquakes.Chinese J.Geophys.(in Chinese),2005,48(1):116~123
[15]陆明万,罗学富.弹性理论基础.北京:清华大学出版社,1990.410~415Lu MW,Luo XF.Basic Theory of Elasticity(in Chinese).Beijing:Tsinghua University Press,1990.410~415
[16]Harris R A.Introduction to special session:stress triggers,stress shadows and implications for seismic hazard.J.Geophys.Res.,1998,103:24347~24358
[17]唐春安,徐小荷.岩石破裂的前兆变形率、前兆应力降及临震前兆.地壳形变与地震,1990,10(3):12~18Tang C A,Xu X H.Precursory deformation rate and stress drop in fracture experiments of brittle rocks and earthquake precursory.Crustal Deformation and Earthquake(in Chinese),1990,10(3):12~18
[18]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.北京:地震出版社,1982Editing Group of Tangshan Earthquake on1976,State Seismological Bureau.Tangshan Earthquake on1976(in Chinese).Beijing:Seismological Press,1982
[19]邱泽华,石耀霖.观测应变阶在地震触发研究中的应用.地震学报,2004,26(5):481~488Qiu Z H,Shi YL.Application of observed strain steps to the study of remote earthquake stress triggering.Acta Seismologica Sinica(in Chinese),2004,26(5):481~488
[20]张之立,李钦祖,谷继成等.唐山地震的破裂过程及其力学分析.地震学报,1980,2(2):111~129Zhang Z L,Li Q Z,Gu J C,et al.The fracture processes of the Tangshan earthquake and its mechanical analysis.Acta Seismologica Sinica(in Chinese),1980,2(2):111~129
[21]许力生,陈运泰.1997年中国西藏玛尼MS7·9地震的时空破裂过程.地震学报,1999,21(5):449~459Xu LS,Chen YT.Tempo-spatial rupture process of the1997Mani,Xizang(Tibet),China earthquake ofMS7·9·Acta Seismologica Sinica(in Chinese),1999,21(5):449~459
[22]陈运泰,黄立人,林邦慧等.用大地测量结果反演唐山7·8级主震位错模型.地球物理学报,1979,22(3):201~217Chen YT,Huang L R,Lin B H,et al.Adislocation model of the Tangshan earthquake of1976fromthe inversion of geodetic data.Chinese J.Geophys.(in Chinese),1979,22(3):201~217
[23]国家地震局科研处.唐山地震考察与研究.北京:地震出版社,1981.410~415Office of Scientific Research,State Seismological Bureau.Inspect and Study on Tangshan Earthquake(in Chinese).Beijing:Seismological Press,1981.410~415
[24]李学政,刘文学,沈旭峰.爆炸余震波形持时和余震事件频度模型.地震学报,2004,26(5):539~546Li XZ,Liu WX,Shen WX.Models of wave duration and event frequency of explosion aftershocks.Acta Seismologica Sinica(in Chinese),2004,26(5):539~546
[25]Freed A M,Lin J.Delayed triggering of the1999Hector Mine earthquake by viscoelastic stresstransfer.Nature,2001,411:180~183
[2]沈正康,万永革,甘卫军等.东昆仑活动断裂带大地震之间的黏弹性应力触发研究.地球物理学报,2003,46(6):786~795Shen Z K,Wan YG,Gan WJ,et al.Viscoelastic triggering among large earthquakes along the east Kunlun fault system.Chinese J.Geophys.(in Chinese),2003,46(6):786~795
[3]Hill D P,Reasenberg P A,Michael A,et al.Seismicity remotely triggered by the magnitude7·3Landers,California earthquake.Science,1993,260:1617~1623
[4]Pollitz F F,Sacks I S.The1995Kobe,Japan earthquake:a long-delayed aftershock of the offshore1994Tonankai and1946Nankaido earthquakes.Bull.Seism.Soc.Am.,1997,87:1~10
[5]Mohamad R,Darkal A N,Seber D,et al.Remote earthquake triggering alongthe Dead Seafault in Syriafollowingthe1995Gulf of Aqaba earthquake(Ms=7·3).Seismol.Res.Lett.,2000,71:47~52
[6]Cotton F,Coutant O.Dynamic stress variations due to shear faultsin a plane-layered medium.Geophys.J.Int.,1997,128:676~688
[7]Kilb D,Gomberg J,Bodin P.Earthquake triggering by dynamic stresses.Nature,2000,408:570~574
[8]Rigobert T,Douglas A W,Hiroshi I.Remote triggering of deep earthquakes in the2002Tonga sequences.Nature,2003,424(6951):921~925
[9]Byerlee J.Model for episodic flow of high pressure water in fault zones before earthquakes.Geology,1993,21:303~306
[10]Gomberg J.The failure of earthquake failure models.J.Geophys.Res.,2001,106(B8):16253~16263
[11]Sturtevant B,Kanamori H,Brodsky E E.Seismic triggering by rectified diffusionin geothermal systems.J.Geophys.Res.,1996,101:25269~25282
[12]万永革,吴忠良,周公威等.地震应力触发研究.地震学报,2002,24(5):533~551Wan Y G,Wu Z L,Zhou G W,et al.Research on seismic stress triggering.Acta Seismologia Sinica(in Chinese),2002,24(5):533~551
[13]陆明勇,郑文衡.地壳块体动应力演化特征及其与地震关系的初步研究.地震学报,2005,27(3):282~291Lu MY,Zheng WH.Preliminary study on variation characteristics of ocean tide dynamic stress in crust and its relationship with earthquakes.Acta Seismologia Sinica,2005,18(3):303~312
[14]郑文衡,陆明勇.地震动态触发机制的初步研究.地球物理学报,2005,48(1):116~123Zheng WH,Lu MY.Apreliminary study on mechanismof dynamic triggering of earthquakes.Chinese J.Geophys.(in Chinese),2005,48(1):116~123
[15]陆明万,罗学富.弹性理论基础.北京:清华大学出版社,1990.410~415Lu MW,Luo XF.Basic Theory of Elasticity(in Chinese).Beijing:Tsinghua University Press,1990.410~415
[16]Harris R A.Introduction to special session:stress triggers,stress shadows and implications for seismic hazard.J.Geophys.Res.,1998,103:24347~24358
[17]唐春安,徐小荷.岩石破裂的前兆变形率、前兆应力降及临震前兆.地壳形变与地震,1990,10(3):12~18Tang C A,Xu X H.Precursory deformation rate and stress drop in fracture experiments of brittle rocks and earthquake precursory.Crustal Deformation and Earthquake(in Chinese),1990,10(3):12~18
[18]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.北京:地震出版社,1982Editing Group of Tangshan Earthquake on1976,State Seismological Bureau.Tangshan Earthquake on1976(in Chinese).Beijing:Seismological Press,1982
[19]邱泽华,石耀霖.观测应变阶在地震触发研究中的应用.地震学报,2004,26(5):481~488Qiu Z H,Shi YL.Application of observed strain steps to the study of remote earthquake stress triggering.Acta Seismologica Sinica(in Chinese),2004,26(5):481~488
[20]张之立,李钦祖,谷继成等.唐山地震的破裂过程及其力学分析.地震学报,1980,2(2):111~129Zhang Z L,Li Q Z,Gu J C,et al.The fracture processes of the Tangshan earthquake and its mechanical analysis.Acta Seismologica Sinica(in Chinese),1980,2(2):111~129
[21]许力生,陈运泰.1997年中国西藏玛尼MS7·9地震的时空破裂过程.地震学报,1999,21(5):449~459Xu LS,Chen YT.Tempo-spatial rupture process of the1997Mani,Xizang(Tibet),China earthquake ofMS7·9·Acta Seismologica Sinica(in Chinese),1999,21(5):449~459
[22]陈运泰,黄立人,林邦慧等.用大地测量结果反演唐山7·8级主震位错模型.地球物理学报,1979,22(3):201~217Chen YT,Huang L R,Lin B H,et al.Adislocation model of the Tangshan earthquake of1976fromthe inversion of geodetic data.Chinese J.Geophys.(in Chinese),1979,22(3):201~217
[23]国家地震局科研处.唐山地震考察与研究.北京:地震出版社,1981.410~415Office of Scientific Research,State Seismological Bureau.Inspect and Study on Tangshan Earthquake(in Chinese).Beijing:Seismological Press,1981.410~415
[24]李学政,刘文学,沈旭峰.爆炸余震波形持时和余震事件频度模型.地震学报,2004,26(5):539~546Li XZ,Liu WX,Shen WX.Models of wave duration and event frequency of explosion aftershocks.Acta Seismologica Sinica(in Chinese),2004,26(5):539~546
[25]Freed A M,Lin J.Delayed triggering of the1999Hector Mine earthquake by viscoelastic stresstransfer.Nature,2001,411:180~183
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