断裂两盘岩性差异对汶川地震的影响
|
摘要
岩性差异导致层间变形差异是常见的构造变形现象.龙门山断裂带中段北川—映秀断裂虹口至清平段,断裂上盘为坚硬的前震旦系褶皱基底,下盘则为软弱的前陆盆地沉积物,两者之间具有较大的岩性差异.本文利用基于R-minimum的有限元算法对在一个地震复发间隔内的断层活动进行非线性摩擦接触模拟.计算结果显示,上下盘泊松比的差异则对断层破裂时间及快体变形影响不大,但不同的泊松比条件下断层的破裂过程略有不同,而上下盘杨氏模量的差异能够延迟断层的破裂时间,延长破裂过程,扩大地震复发间隔,且扩大了下盘深度10km以上和10km以下地层变形的差异.双断坡构造能够通过深部的应力分解来削弱断层下盘深度10km以上的变形,但是在上下盘岩性一致的情况下,双断坡构造推迟了主断层的滑动时间,延长了破裂过程,而在强硬上盘和软弱下盘共存的条件下,发育于软弱下盘的次级破裂并不能对主断层的破裂时间和破裂过程造成较大影响.北川—映秀断裂上盘强硬的彭灌杂岩和下盘软弱的含碳沉积地层对汶川地震双断坡式破裂的生成具有重要的促进作用.
It is a common phenomenon that lithologic differences cause different deformation between layers.This work focuses on the Longmenshan thrust zone,which is located at the eastern margin of the Tibet plateau.The 2008 Wenchuan earthquake occurred at the middle segment of the Longmenshan thrust zone,which is called Beichuan-Yingxiu fault.The section of Hongkou to Qingping of the Beichuan-Yingxiu fault is a thick skinned thrust fault in the interface of Precambrian Complex and stratified rock.There is large difference in material between the hanging wall and footwall.Based on the seismic reflection profile,focal mechanism solutions and coseismic surface ruptures of the Wenchuan earthquake,two two-dimensional models constrained by the low-resistivity and low-velocity layers were built across the Beichuan-Yingxiu fault to study the influence of dissimilar materials.We use the R-minimum strategy based the nonlinear finite element method to simulate contact behavior of the fault and deformation style in the upper crust in the time period of one earthquake recurrence interval.Totally 24 couples of different Young′s modules of the hanging wall and footwall were tested.The results show the interaction of the tough complex in the hanging wall and carbon-containing stratified rock in the footwall.The difference in the Young′s modules between the hanging wall and the footwall could increase the slip time of the fault,prolong slip progress and cause more vertical deformation at the depth less than 10 km in the footwall.On the other hand,the difference in the Poisson ratio has little effect on the fault behavior,but seems to have some influence on the slip progress.When the seismogenic structure is in the interface of dissimilar materials,the activity of fractures developed in the foreland basin in front of the thrust belt has limited effects both on the slip time and slip progress of the thrust fault,but they could decrease the deformation of layers shallower than 10 km in the footwall through slip partitioning.The tough Pengguan complex in the hanging wall and the soft stratified rock is one of the key factors of the two imbricate structures ruptured in the Wenchuan earthquake.
It is a common phenomenon that lithologic differences cause different deformation between layers.This work focuses on the Longmenshan thrust zone,which is located at the eastern margin of the Tibet plateau.The 2008 Wenchuan earthquake occurred at the middle segment of the Longmenshan thrust zone,which is called Beichuan-Yingxiu fault.The section of Hongkou to Qingping of the Beichuan-Yingxiu fault is a thick skinned thrust fault in the interface of Precambrian Complex and stratified rock.There is large difference in material between the hanging wall and footwall.Based on the seismic reflection profile,focal mechanism solutions and coseismic surface ruptures of the Wenchuan earthquake,two two-dimensional models constrained by the low-resistivity and low-velocity layers were built across the Beichuan-Yingxiu fault to study the influence of dissimilar materials.We use the R-minimum strategy based the nonlinear finite element method to simulate contact behavior of the fault and deformation style in the upper crust in the time period of one earthquake recurrence interval.Totally 24 couples of different Young′s modules of the hanging wall and footwall were tested.The results show the interaction of the tough complex in the hanging wall and carbon-containing stratified rock in the footwall.The difference in the Young′s modules between the hanging wall and the footwall could increase the slip time of the fault,prolong slip progress and cause more vertical deformation at the depth less than 10 km in the footwall.On the other hand,the difference in the Poisson ratio has little effect on the fault behavior,but seems to have some influence on the slip progress.When the seismogenic structure is in the interface of dissimilar materials,the activity of fractures developed in the foreland basin in front of the thrust belt has limited effects both on the slip time and slip progress of the thrust fault,but they could decrease the deformation of layers shallower than 10 km in the footwall through slip partitioning.The tough Pengguan complex in the hanging wall and the soft stratified rock is one of the key factors of the two imbricate structures ruptured in the Wenchuan earthquake.
引文
[1]Gudmundsson A.Effects of Young′s modulus on faultdisplacement.Comptes Rendus Géosciences,2004,361(1):85-92.
[2]Ben-Zion Y,Andrews D J.Properties and implications ofdynamic rupture along a material interface.Bulletin of theSeismological Society of America,1998,88(4),1085-1094.
[3]Ben-Zion Y.Dynamic ruptures in recent models of earthquakefaults.Journal of the Mechanics and Physics of Solids,2001,49(9):2209-2244.
[4]Ben-Zion Y,Shi Z Q.Dynamic rupture on a materialinterface with spontaneous generation of plastic strain in thebulk.Earth and Planetary Science Letters,2005,236(1-2):486-496.
[5]王萍,付碧宏,张斌等.汶川8.0级地震地表破裂带与岩性关系.地球物理学报,2009,52(1):131-139.Wang P,Fu B H,Zhang B,et al.Relationships betweensurface ruptures and lithologic characteristics of the WenchuanMs8.0earthquake.Chinese J.Geophys.(in Chinese),2009,52(1):131-139.
[6]Xu X W,Wen X Z,Yu G H,et al.Co-seismic reverse andoblique-slip surface faulting generated by the 2008 Mw7.9Wenchuan earthquake,China.Geology,2009,37(6),515-518.
[7]陈桂华,徐锡伟,于贵华等.2008年汶川MS8.0地震多断裂破裂的近地表同震滑移及滑移分解.地球物理学报,2009,52(5):1384-1394.Chen G H,Xu X W,Yu G H,et al.Co-seismic slip and slippartitioning of multi-faults during the Ms8.0 2008Wenchuanearthquake.Chinese J.Geophys.(in Chinese),2009,52(5):1384-1394.
[8]Li Y,Allen P A,Densmore A L,et al.Evolution of theLongmen Shan foreland basin(Western Sichuan,China)during the late Triassic Indosinian Orogeny.Basin Research,2003,15:117-138.
[9]贾东,陈竹新,贾承造等.龙门山前陆褶皱冲断带构造解析与川西前陆盆地的发育.高校地质学报,2003,9(3):402-410.Jia D,Chen Z X,Jia C Z,et al.Structural features of theLongmen Shan Fold and thrust belt and development of thewestern Sichuan foreland basin,central China.GeologicalJournal of China Universities(in Chinese),2003,9(3):402-410.
[10]林茂炳,马永旺.论龙门山彭灌杂岩体的构造属性.成都理工学院学报,1995,22(1):42-46.Lin M B,Ma Y W.A discussion on the tectonic characteristicsof Peng-Guan Complex in Longmen Mountains.Journal ofChengdu Institute of Technology(in Chinese),1995,22(1):42-46.
[11]Jia D,Li Y Q,Lin A M,et al.Structural model of 2008Mw7.9 Wenchuan earthquake in the rejuvenated LongmenShan thrust belt,China.Tectonophysics,2010,491(1-4):174-184.
[12]Li Q S,Gao R,Wang H Y,et al.Deep background ofWenchuan Earthquake and the upper crust structure beneaththe Longmen Shan and adjacent areas.Acta GeologicaSinica,2009,83(4):733-739.
[13]Xing H L,Makinouchi A.Finite-element modeling ofmultibody contact and its application to active faults.Concurrency and Computation:Practice and Experience,2002,14(6-7):431-450.
[14]Xing H L,Makinouchi A.Finite element modelling offrictional instability between deformable rocks.Int.J.Numer.Anal.Meth.Geomech,2003,27(12):1005-1025.
[15]Xing H L,Makinouchi A,MORA P.Finite elementmodeling of interacting fault systems.Physics of the Earthand Planetary Interiors,2007,163(1-4):106-121.
[16]Dieterich J H.Modeling of rock friction.1.Experimentalresults and constitutive equations.J.Geophys.Res.,1979,84(B5):2161-2168.
[17]Ruina A.Slip instability and state variable friction laws.J.Grophys.Res.,1983,88(B12):10359-10370.
[18]Scholz C H.Earthquakes and friction laws.Nature,1998,391(6662):37-42.
[19]刘超,张勇,许力生等.一种矩张量反演新方法及其对2008年汶川Ms8.0地震序列的应用.地震学报,2008,30(4):329-339.Liu C,Zhang Y,Xu L S,et al.A new technique for momenttensor inversion with applications to the 2008 WenchuanMS8.0earthquake sequence.Acta Seismologica Sinica(inChinese),2008,30(4):329-339.
[20]张勇,许力生,陈运泰.2008年汶川大地震震源机制的时空变化.地球物理学报,2009,52(2):379-389.Zhang Y,Xu L S,Chen Y T.Spatio-temporal variation ofthe source mechanism of the 2008 great Wenchuanearthquake.Chinese J.Gephys.(in Chinese),2009,52(2):379-389.
[21]王卫民,赵连锋,李娟等.四川汶川8.0级地震震源过程.地球物理学报,2008,51(5):1403-1410.Wang W M,Zhao L F,Li J,et al.Rupture process of theMs8.0Wenchuan earthquake of Sichuan,China.Chinese J.Geophys.(in Chinese),2008,51(5):1403-1410.
[22]刘树根,李智武,曹俊兴等.龙门山陆内复合造山带的四维结构构造特征.地质科学,2009,44(4):1151-1180.Liu S G,Li Z W,Cao J X.et al.4-D textural and structuralcharacteristics of Longmen intracontinental composite orogenicbelt,southwest China.Chinese Journal of Geology(inChinese),2009,44(4):1151-1180.
[23]刘静,曾令森,丁林等.青藏高原东南缘构造地貌、活动构造和下地壳流动假说.地质科学,2009,44(4):1227-1255.Liu J,Zeng L S,Ding L,et al.Tectonic geomorphology,active tectonics and lower crustal channel flow hypothesis ofthe southeastern Tibetan Plateau.Chinese Journal ofGeology(in Chinese),2009,44(4):1227-1255.
[24]张培震,徐锡伟,闻学泽等.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.地球物理学报,2008,51(4):1066-1073.Zhang P Z,Xu X W,Wen X Z,et al.Slip rates andrecurrence intervals of the Longmenshan active fault zone,and tectonic implications for the mechanism of the May 122008,Wenchuan earthquake,Sichuan,China.Chinese J.Geophys.(in Chinese),2008,51(4):1066-1073.
[25]李勇,徐公达,周荣军等.龙门山均衡重力异常及其对青藏高原东缘山脉地壳隆升的约束.地质通报,2005,24(12):1162-1168.Li Y,Xu G D,Zhou R J,et al.Isostatic gravity anomalies inthe Longmen Mountains and their constraints on the crustaluplift below the mountains on the eastern margin of theQinghai—Tibet Plateau.Geological Bulletin of China(inChinese),2005,24(12):1162-1168.
[26]王谦身,滕吉文,张永谦等.四川中西部地区地壳结构与重力均衡.地球物理学报,2009,52(2):579-583.Wang Q S,Teng J W,Zhang Y Q,et al.The crustalstructure and gravity isostasy in the middle western Sichuanarea.Chinese J.Geophys.(in Chinese),2009,52(2):579-583.
[27]刘启元,李昱,陈九辉等.汶川Ms8.0地震:地壳上地幔S波速度结构的初步研究.地球物理学报,2009,52(2):309-319.Liu Q Y,Li Y,Chen J H,et al.Wenchuan Ms8.0earthquake:preliminary study of the S-wave velocity structure ofthe crust and upper mantle.Chinese J.Geophys.(in Chinese),2009,52(2):309-319.
[28]Ran Y K,Chen L C,Chen J,et al.Paleoseismic evidenceand repeat time of large earthquakes at three sites along theLongmenshan fault zone.Tectonophysics,2010,491(1-4):141-153.
[29]朱守彪,张培震.2008年汶川MS8.0地震发生过程的动力学机制研究.地球物理学报,2009,52(2):418-427.Zhu S B,Zhang P Z.A study on the dynamical mechanismsof the Wenchuan MS8.0 earthquake,2008.Chinese J.Geophys.(in Chinese),2009,52(2):418-427.
[30]叶金汉.岩石力学参数手册.北京:水利水电出版社,1991.Ye J H.Manual of Rock Mass Parameters(in Chinese).Beijing:China Water Power Press,1991.
[31]张培震,闻学泽,徐锡伟等.2008年汶川8.0级特大地震孕育和发生的多单元组合模式.科学通报,2009,54(7):944-953.Zhang P Z,Wen X Z,Xu X W,et al.Tectonic model of thegreat Wenchuan earthquake of May 12,2008,Sichuan,China.Chinese Science Bulletin(in Chinese),2009,54(7):944-953.
[32]Hao K X,Si H J,Fujiwara H,et al.Coseismic surface-ruptures and crustal deformations of the 2008 Wenchuanearthquake Mw7.9,China.Geophys.Res.Lett.,2009,36:L11303,doi:10.1029/2009GL037971.
[2]Ben-Zion Y,Andrews D J.Properties and implications ofdynamic rupture along a material interface.Bulletin of theSeismological Society of America,1998,88(4),1085-1094.
[3]Ben-Zion Y.Dynamic ruptures in recent models of earthquakefaults.Journal of the Mechanics and Physics of Solids,2001,49(9):2209-2244.
[4]Ben-Zion Y,Shi Z Q.Dynamic rupture on a materialinterface with spontaneous generation of plastic strain in thebulk.Earth and Planetary Science Letters,2005,236(1-2):486-496.
[5]王萍,付碧宏,张斌等.汶川8.0级地震地表破裂带与岩性关系.地球物理学报,2009,52(1):131-139.Wang P,Fu B H,Zhang B,et al.Relationships betweensurface ruptures and lithologic characteristics of the WenchuanMs8.0earthquake.Chinese J.Geophys.(in Chinese),2009,52(1):131-139.
[6]Xu X W,Wen X Z,Yu G H,et al.Co-seismic reverse andoblique-slip surface faulting generated by the 2008 Mw7.9Wenchuan earthquake,China.Geology,2009,37(6),515-518.
[7]陈桂华,徐锡伟,于贵华等.2008年汶川MS8.0地震多断裂破裂的近地表同震滑移及滑移分解.地球物理学报,2009,52(5):1384-1394.Chen G H,Xu X W,Yu G H,et al.Co-seismic slip and slippartitioning of multi-faults during the Ms8.0 2008Wenchuanearthquake.Chinese J.Geophys.(in Chinese),2009,52(5):1384-1394.
[8]Li Y,Allen P A,Densmore A L,et al.Evolution of theLongmen Shan foreland basin(Western Sichuan,China)during the late Triassic Indosinian Orogeny.Basin Research,2003,15:117-138.
[9]贾东,陈竹新,贾承造等.龙门山前陆褶皱冲断带构造解析与川西前陆盆地的发育.高校地质学报,2003,9(3):402-410.Jia D,Chen Z X,Jia C Z,et al.Structural features of theLongmen Shan Fold and thrust belt and development of thewestern Sichuan foreland basin,central China.GeologicalJournal of China Universities(in Chinese),2003,9(3):402-410.
[10]林茂炳,马永旺.论龙门山彭灌杂岩体的构造属性.成都理工学院学报,1995,22(1):42-46.Lin M B,Ma Y W.A discussion on the tectonic characteristicsof Peng-Guan Complex in Longmen Mountains.Journal ofChengdu Institute of Technology(in Chinese),1995,22(1):42-46.
[11]Jia D,Li Y Q,Lin A M,et al.Structural model of 2008Mw7.9 Wenchuan earthquake in the rejuvenated LongmenShan thrust belt,China.Tectonophysics,2010,491(1-4):174-184.
[12]Li Q S,Gao R,Wang H Y,et al.Deep background ofWenchuan Earthquake and the upper crust structure beneaththe Longmen Shan and adjacent areas.Acta GeologicaSinica,2009,83(4):733-739.
[13]Xing H L,Makinouchi A.Finite-element modeling ofmultibody contact and its application to active faults.Concurrency and Computation:Practice and Experience,2002,14(6-7):431-450.
[14]Xing H L,Makinouchi A.Finite element modelling offrictional instability between deformable rocks.Int.J.Numer.Anal.Meth.Geomech,2003,27(12):1005-1025.
[15]Xing H L,Makinouchi A,MORA P.Finite elementmodeling of interacting fault systems.Physics of the Earthand Planetary Interiors,2007,163(1-4):106-121.
[16]Dieterich J H.Modeling of rock friction.1.Experimentalresults and constitutive equations.J.Geophys.Res.,1979,84(B5):2161-2168.
[17]Ruina A.Slip instability and state variable friction laws.J.Grophys.Res.,1983,88(B12):10359-10370.
[18]Scholz C H.Earthquakes and friction laws.Nature,1998,391(6662):37-42.
[19]刘超,张勇,许力生等.一种矩张量反演新方法及其对2008年汶川Ms8.0地震序列的应用.地震学报,2008,30(4):329-339.Liu C,Zhang Y,Xu L S,et al.A new technique for momenttensor inversion with applications to the 2008 WenchuanMS8.0earthquake sequence.Acta Seismologica Sinica(inChinese),2008,30(4):329-339.
[20]张勇,许力生,陈运泰.2008年汶川大地震震源机制的时空变化.地球物理学报,2009,52(2):379-389.Zhang Y,Xu L S,Chen Y T.Spatio-temporal variation ofthe source mechanism of the 2008 great Wenchuanearthquake.Chinese J.Gephys.(in Chinese),2009,52(2):379-389.
[21]王卫民,赵连锋,李娟等.四川汶川8.0级地震震源过程.地球物理学报,2008,51(5):1403-1410.Wang W M,Zhao L F,Li J,et al.Rupture process of theMs8.0Wenchuan earthquake of Sichuan,China.Chinese J.Geophys.(in Chinese),2008,51(5):1403-1410.
[22]刘树根,李智武,曹俊兴等.龙门山陆内复合造山带的四维结构构造特征.地质科学,2009,44(4):1151-1180.Liu S G,Li Z W,Cao J X.et al.4-D textural and structuralcharacteristics of Longmen intracontinental composite orogenicbelt,southwest China.Chinese Journal of Geology(inChinese),2009,44(4):1151-1180.
[23]刘静,曾令森,丁林等.青藏高原东南缘构造地貌、活动构造和下地壳流动假说.地质科学,2009,44(4):1227-1255.Liu J,Zeng L S,Ding L,et al.Tectonic geomorphology,active tectonics and lower crustal channel flow hypothesis ofthe southeastern Tibetan Plateau.Chinese Journal ofGeology(in Chinese),2009,44(4):1227-1255.
[24]张培震,徐锡伟,闻学泽等.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.地球物理学报,2008,51(4):1066-1073.Zhang P Z,Xu X W,Wen X Z,et al.Slip rates andrecurrence intervals of the Longmenshan active fault zone,and tectonic implications for the mechanism of the May 122008,Wenchuan earthquake,Sichuan,China.Chinese J.Geophys.(in Chinese),2008,51(4):1066-1073.
[25]李勇,徐公达,周荣军等.龙门山均衡重力异常及其对青藏高原东缘山脉地壳隆升的约束.地质通报,2005,24(12):1162-1168.Li Y,Xu G D,Zhou R J,et al.Isostatic gravity anomalies inthe Longmen Mountains and their constraints on the crustaluplift below the mountains on the eastern margin of theQinghai—Tibet Plateau.Geological Bulletin of China(inChinese),2005,24(12):1162-1168.
[26]王谦身,滕吉文,张永谦等.四川中西部地区地壳结构与重力均衡.地球物理学报,2009,52(2):579-583.Wang Q S,Teng J W,Zhang Y Q,et al.The crustalstructure and gravity isostasy in the middle western Sichuanarea.Chinese J.Geophys.(in Chinese),2009,52(2):579-583.
[27]刘启元,李昱,陈九辉等.汶川Ms8.0地震:地壳上地幔S波速度结构的初步研究.地球物理学报,2009,52(2):309-319.Liu Q Y,Li Y,Chen J H,et al.Wenchuan Ms8.0earthquake:preliminary study of the S-wave velocity structure ofthe crust and upper mantle.Chinese J.Geophys.(in Chinese),2009,52(2):309-319.
[28]Ran Y K,Chen L C,Chen J,et al.Paleoseismic evidenceand repeat time of large earthquakes at three sites along theLongmenshan fault zone.Tectonophysics,2010,491(1-4):141-153.
[29]朱守彪,张培震.2008年汶川MS8.0地震发生过程的动力学机制研究.地球物理学报,2009,52(2):418-427.Zhu S B,Zhang P Z.A study on the dynamical mechanismsof the Wenchuan MS8.0 earthquake,2008.Chinese J.Geophys.(in Chinese),2009,52(2):418-427.
[30]叶金汉.岩石力学参数手册.北京:水利水电出版社,1991.Ye J H.Manual of Rock Mass Parameters(in Chinese).Beijing:China Water Power Press,1991.
[31]张培震,闻学泽,徐锡伟等.2008年汶川8.0级特大地震孕育和发生的多单元组合模式.科学通报,2009,54(7):944-953.Zhang P Z,Wen X Z,Xu X W,et al.Tectonic model of thegreat Wenchuan earthquake of May 12,2008,Sichuan,China.Chinese Science Bulletin(in Chinese),2009,54(7):944-953.
[32]Hao K X,Si H J,Fujiwara H,et al.Coseismic surface-ruptures and crustal deformations of the 2008 Wenchuanearthquake Mw7.9,China.Geophys.Res.Lett.,2009,36:L11303,doi:10.1029/2009GL037971.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心