1997年玛尼地震对青藏川滇地区构造块体系统稳定性影响的三维DDA+FEM方法数值模拟
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摘要
本文用三维非连续变形与有限元相结合(DDA+FEM)的方法,在青藏川滇地区三维构造块体相互制约的大背景中,通过用GPS资料做位移速率边界约束和震源机制约束,计算得到研究区的初始位移场和应力场与该地区GPS测量结果和震源机制分布结果基本一致.在此基础上进一步数值模拟1997年玛尼7.9级大震的发生过程,研究大震引起研究区各块体边界断层应力状态变化的特征.(1)发震断层两侧发生左旋走滑错动,最大水平位错大约7m;(2)深部位错面上位错分布与用地震波资料震源反演的结果类似;(3)最大差应力变化等值线图与由星载D-INSAR技术获取的地表形变场图像相似;(4)地表垂直位移表明地震断层面略向北逆冲.计算模拟得到了玛尼地震发生引起青藏川滇地区构造块体系统各边界断层上库仑破裂应力变化的分布,表明玛尼大震的发生除了使其发震断层的两端库仑破裂应力增大,应力进一步集中外,位于上地壳层上东昆仑断裂中段的2001年昆仑山8.1大震(H=11km)发震断层段的库仑破裂应力增加约2MPa,位于中地壳层上喀拉昆仑断裂带中的2008年改则6.9级地震(H=30km)发震断层段的库仑破裂应力也增加约0.7MPa,可见这两个已接近破裂强度地段的失稳对发生大震起了一定促进作用.研究结果也表明:作者发展的三维DDA+FEM方法能有效地用于大震活动与各构造块体相互作用关系的研究.
Using 3-D Finite Element Method combined with Discontinuous Deformation Analysis,in large background of interaction among 3-D tectonic blocks in Qingzang and Chuandian zone,based on the GPS data and seismic focal mechanism,we compute initial displacement field and stress field in the studied zone,which agree basically with the results of GPS measurement and seismic focal mechanism distribution.Further the occurrence process of 1997 Mani earthquake with magnitude Ms7.9 is simulated numerically,and feature of stress state change on each boundary fault of blocks is studied.(1)The maximum horizontal dislocation is 7 m with left rotation and strike;(2)The distribution of dislocation on vertical face of the seismic fault is totally similar with the inversion result from seismic wave information;(3)Maximum shear stresses contour is similar with the deformation field from D-INSAR;(4)The vertical displacement distribution computed on the surface across fault indicates that the fault sliding is adverse to north.Furthermore,distribution of Coulomb failure stress change on the boundary faults of Qingzang and Chuandian block system after Mani earthquake is calculated.It indicates that the Mani earthquake,except making Coulomb failure stress increase and stress concentration in ends of the seismic fault,causes Coulomb failure stress in upper crust layer to increase about 2MPa at the seismic fault where Kunlun Shan Ms7.9 earthquake(H=11 km)located at mid section of eastern Kunlun fracture occurred in 2002.and causes Coulomb failure stress in middle crust layer to increase about 0.7MPa at the seismic fault where Gêrzê Ms6.9 earthquake(H=30 km)located at Karakorum fracture zone occurred in 2008.It seems to indicate that Mani earthquake has positive function to the two zones close to rupture strength and afterward occurrence of the two earthquake.The research results also indicate that 3-D DDA+FEM method developed by authors is available to apply in studying relationship between large earthquake occurrence and interaction of tectonic blocks.
Using 3-D Finite Element Method combined with Discontinuous Deformation Analysis,in large background of interaction among 3-D tectonic blocks in Qingzang and Chuandian zone,based on the GPS data and seismic focal mechanism,we compute initial displacement field and stress field in the studied zone,which agree basically with the results of GPS measurement and seismic focal mechanism distribution.Further the occurrence process of 1997 Mani earthquake with magnitude Ms7.9 is simulated numerically,and feature of stress state change on each boundary fault of blocks is studied.(1)The maximum horizontal dislocation is 7 m with left rotation and strike;(2)The distribution of dislocation on vertical face of the seismic fault is totally similar with the inversion result from seismic wave information;(3)Maximum shear stresses contour is similar with the deformation field from D-INSAR;(4)The vertical displacement distribution computed on the surface across fault indicates that the fault sliding is adverse to north.Furthermore,distribution of Coulomb failure stress change on the boundary faults of Qingzang and Chuandian block system after Mani earthquake is calculated.It indicates that the Mani earthquake,except making Coulomb failure stress increase and stress concentration in ends of the seismic fault,causes Coulomb failure stress in upper crust layer to increase about 2MPa at the seismic fault where Kunlun Shan Ms7.9 earthquake(H=11 km)located at mid section of eastern Kunlun fracture occurred in 2002.and causes Coulomb failure stress in middle crust layer to increase about 0.7MPa at the seismic fault where Gêrzê Ms6.9 earthquake(H=30 km)located at Karakorum fracture zone occurred in 2008.It seems to indicate that Mani earthquake has positive function to the two zones close to rupture strength and afterward occurrence of the two earthquake.The research results also indicate that 3-D DDA+FEM method developed by authors is available to apply in studying relationship between large earthquake occurrence and interaction of tectonic blocks.
引文
[1]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 L S,Chen Y T.Tempo-spatial rupture process of the1997,Mani,Xizang(Tibet),China earthquake ofMs=7.9.Acta Seismologica Sinica,1999,10(2):495～506
[2]单新建,李建华,张桂芳.1997年玛尼7.9级地震的构造环境和地表破裂带特征.地球物理学报,2006,49(3):831～837Shan XJ,Li J H,Zhang G F.The tectonic condition and the feature of surface rupture zone of the mani earthquake(Ms7.9)in1997.Chinese J.Geophys.(in Chinese),2006,40(3):831～837
[3]单新建,马瑾,王长林等.利用星载D-I NSAR技术获取的地表形变场提取玛尼地震震源断层参数.中国科学(D),2002,32(10):837～844Shan X J,Ma J,Wang C L,et al.Co-seismic ground deformation and source parameters of ManiM7.9earthquakeinferred fromspaceborne D-InSAR observation data.Science in China(D)(in Chinese),2002,32(10):837～844
[4]万永革,沈正康,甘卫军等.东昆仑活动断裂带大地震之间的弹性应力触发研究.西北地震学报,2003,25(1):1～7Wan Y G,Shen Z K,Gan WJ,et al.Study on the elastic stress triggering among the large earthquakes in eastern Kunlun active fault zone.Northwestern Seismological Journal(in Chinese),2003,25(1):1～7
[5]张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学(D),2003,33(增刊):12～20Zhang P Z,Deng Q D,Zhang G M,et al.Active tectonic blocks and strong earthquakes in the continent of China.Science in China(D),2003,46(Suppl.):13～24
[6]石根华.数值流形方法与非连续变形分析.北京:清华大学出版社.1997Shi G H.Numerical Manifold Method and Discontinuous Deformation Analysis(in Chinese).Beijing:Qinhua University Press,1997
[7]陈祖安,白武明,林邦慧等.1966年以来华北地区一系列七级大震破裂过程的数值模拟.地球物理学报,2003,46(3):373～381Chen Z A,Bai W M,Lin B H,et al.Numerical simulation for rupture processes of a series of strong earthquakes(Ms>7)in North China since1966.Chinese J.Geophys.(in Chinese),2003,46(3):373～381
[8]白武明,林邦慧,陈祖安.1976年唐山大震发生对华北地区各地块运动与变形影响的数值模拟研究.中国科学,2003,33(Suppl.):99～107Bai W M,Lin B H,Chen Z A.Numerical simulations of deformation and movement of blocks within North China in response to1976Tangshan earthquake.Science in China(D),2003,46(Suppl.):141～152
[9]王勖成.有限单元法.北京:清华大学出版社.2003Wang X C.Finite Element Method(in Chinese).Beijing:Tsinghua University Press,2003
[10]滕吉文.固体地球物理学概论.北京:地震出版社,2003Teng J W.Introduction to Solid Geophysics(in Chinese).Beijing:Seismological Press,2003
[11]丁志峰,何正勤,吴建平等.青藏高原地震波三维速度结构的研究.中国地震,2001,17(2):202～209Ding Z F,He Z Q,Wu J P,et al.Research on the3-D seismic velocity structures in Qinghai-Xizang plateau.Earthquake Research in China(in Chinese),2001,17(2):202～209
[12]Shen Z K,Zhao C K,Yin A,et al.Contemporary crustal deformation in east Asia constrainedby Global Position System measurements.J.Geophys.Res.2000,105(3):5721～5734
[13]许忠淮.东亚地区现今构造应力图的编制.地震学报,2001,23(5):492～501Xu Z H.A present-day tectonic stress map for eastern Asia region.Acta Seismologica Sinica(in Chinese),2001,23(5):492～501
[14]万永革,沈正康,曾跃华等.青藏高原东北部的库仑应力积累演化对大地震发生的影响.地震学报,2007,29(2):115～129Wan Y G,Shen Z K,Zeng Y H,et al.Evolution of cumulative coulomb failure stress in northeastern Qinghai-Xizang(Tibetan)plateau and its effect on large earthquake occurrence.Acta Seismologica Sinica(in Chinese),2007,29(2):115～129
[15]Papadimitriou E E,Sykes L R.Evolution of the stress field in the northern Aegean Sea(Greece).Geophys J Int,2001,146:747～759
[2]单新建,李建华,张桂芳.1997年玛尼7.9级地震的构造环境和地表破裂带特征.地球物理学报,2006,49(3):831～837Shan XJ,Li J H,Zhang G F.The tectonic condition and the feature of surface rupture zone of the mani earthquake(Ms7.9)in1997.Chinese J.Geophys.(in Chinese),2006,40(3):831～837
[3]单新建,马瑾,王长林等.利用星载D-I NSAR技术获取的地表形变场提取玛尼地震震源断层参数.中国科学(D),2002,32(10):837～844Shan X J,Ma J,Wang C L,et al.Co-seismic ground deformation and source parameters of ManiM7.9earthquakeinferred fromspaceborne D-InSAR observation data.Science in China(D)(in Chinese),2002,32(10):837～844
[4]万永革,沈正康,甘卫军等.东昆仑活动断裂带大地震之间的弹性应力触发研究.西北地震学报,2003,25(1):1～7Wan Y G,Shen Z K,Gan WJ,et al.Study on the elastic stress triggering among the large earthquakes in eastern Kunlun active fault zone.Northwestern Seismological Journal(in Chinese),2003,25(1):1～7
[5]张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学(D),2003,33(增刊):12～20Zhang P Z,Deng Q D,Zhang G M,et al.Active tectonic blocks and strong earthquakes in the continent of China.Science in China(D),2003,46(Suppl.):13～24
[6]石根华.数值流形方法与非连续变形分析.北京:清华大学出版社.1997Shi G H.Numerical Manifold Method and Discontinuous Deformation Analysis(in Chinese).Beijing:Qinhua University Press,1997
[7]陈祖安,白武明,林邦慧等.1966年以来华北地区一系列七级大震破裂过程的数值模拟.地球物理学报,2003,46(3):373～381Chen Z A,Bai W M,Lin B H,et al.Numerical simulation for rupture processes of a series of strong earthquakes(Ms>7)in North China since1966.Chinese J.Geophys.(in Chinese),2003,46(3):373～381
[8]白武明,林邦慧,陈祖安.1976年唐山大震发生对华北地区各地块运动与变形影响的数值模拟研究.中国科学,2003,33(Suppl.):99～107Bai W M,Lin B H,Chen Z A.Numerical simulations of deformation and movement of blocks within North China in response to1976Tangshan earthquake.Science in China(D),2003,46(Suppl.):141～152
[9]王勖成.有限单元法.北京:清华大学出版社.2003Wang X C.Finite Element Method(in Chinese).Beijing:Tsinghua University Press,2003
[10]滕吉文.固体地球物理学概论.北京:地震出版社,2003Teng J W.Introduction to Solid Geophysics(in Chinese).Beijing:Seismological Press,2003
[11]丁志峰,何正勤,吴建平等.青藏高原地震波三维速度结构的研究.中国地震,2001,17(2):202～209Ding Z F,He Z Q,Wu J P,et al.Research on the3-D seismic velocity structures in Qinghai-Xizang plateau.Earthquake Research in China(in Chinese),2001,17(2):202～209
[12]Shen Z K,Zhao C K,Yin A,et al.Contemporary crustal deformation in east Asia constrainedby Global Position System measurements.J.Geophys.Res.2000,105(3):5721～5734
[13]许忠淮.东亚地区现今构造应力图的编制.地震学报,2001,23(5):492～501Xu Z H.A present-day tectonic stress map for eastern Asia region.Acta Seismologica Sinica(in Chinese),2001,23(5):492～501
[14]万永革,沈正康,曾跃华等.青藏高原东北部的库仑应力积累演化对大地震发生的影响.地震学报,2007,29(2):115～129Wan Y G,Shen Z K,Zeng Y H,et al.Evolution of cumulative coulomb failure stress in northeastern Qinghai-Xizang(Tibetan)plateau and its effect on large earthquake occurrence.Acta Seismologica Sinica(in Chinese),2007,29(2):115～129
[15]Papadimitriou E E,Sykes L R.Evolution of the stress field in the northern Aegean Sea(Greece).Geophys J Int,2001,146:747～759
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