2008年汶川地震断层北川段的几何学与运动学特征及地震地质灾害效应
摘要
2008年5月12日M_S8.0汶川大地震的主要发震断层是龙门山断裂带的映秀—北川断裂.本研究通过地震后的实地调查和地震前后高空间分辨率航空与卫星影像的解译,对映秀—北川断裂带北川段(擂鼓镇—曲山镇)同震地表破裂带的几何学与运动学特征及相关地震地质灾害进行了详细分析.研究结果表明5·12汶川大地震沿映秀—北川断裂带产生的地表破裂带正穿过北川县城曲山镇中心,并在曲山镇周围诱发了一系列大型滑坡和岩崩等地质灾害,致使北川县城遭到毁灭性破坏.野外考察表明北川段最大逆冲量和右旋走滑量都达8-10 m,这也是映秀—北川地表地震破裂带中位移量最大的地段.同时,值得注意的是曲山镇—带正是地震断层几何学和运动学特征改变的转换地带:曲山镇及其南西部断层倾向北西,呈现以逆冲为主兼右旋走滑的特征;在曲山镇北东断层倾向南东,表现为右旋走滑分量与垂直分量相当,走滑活动特征更明显.研究结果还表明,逆冲-走滑型(或斜向逆冲型)同震地表破裂带的儿何学和运动学特征直接影响地震地质灾害及其破坏程度,地震地质灾害的分布表现出明显的不对称性:断层NW盘(上盘)远远强于SE盘(下盘).地震断层的几何学特征与断层运动的应力及坡向的自由面之间相互作用,加强了滑坡、岩崩等地质灾害的破坏力.因此,汶川大地震为我们研究逆冲-走滑型同震地表破裂的几何学、运动学特征及其地震地质灾害效应提供了契机.
The NE-trending Yingxiu-Beichuan and Guanxian-Anxian faults in the Longmen Shan fault zone are responsible for the 12 May 2008 M_S 8. 0 Wenchuan earthquake. Based on the interpretation of post-quake high-resolution remote sensing imagery and field geologic observations, the geometry and kinematics of co-seismic surface rupture as well as the seismic and geologic hazards along the Beichuan segment between Leigu Town and Qushan Town, Beichuan County, are analyzed in detail. Results indicate that surface deformation appears as an oblique thrusting with near equal vertical and right-lateral displacements ranged from 2 to 10 m, in which the largest displacement occurred along this segment in the Yingxiu-Beichuan fault. A notable distribution feature of geologic disasters and building damages induced by this earthquake shows strong hanging wall effects across the surface rupture zone:the highest density of landslides, rock falls, debris flows and building damages occurred on the northwest (hanging wall) side of the fault, but few geologic disasters developed on the southeast (foot wall) side of the fault. These effects are caused directly by the asymmetric fault geometry and the stress interaction between the fault motion and free surface of the slopes. Other factors such as material heterogeneity and spatial variation in frictional properties along the fault strike may further affect the rupture and slip patterns of oblique thrust faulting with a right-lateral strike-slip component. From view of disaster mitigation, the geometry and kinematics of surface rupture zone associated with the M_S 8. 0 Wenchuan earthquake also taught a realistic lesson to how to mitigate potential seismic and geologic disasters associated with future great earthquakes in highly populated region through pre-earthquake analysis and evaluation of active faults using remote sensing technique combined with field reconnaissance.
The NE-trending Yingxiu-Beichuan and Guanxian-Anxian faults in the Longmen Shan fault zone are responsible for the 12 May 2008 M_S 8. 0 Wenchuan earthquake. Based on the interpretation of post-quake high-resolution remote sensing imagery and field geologic observations, the geometry and kinematics of co-seismic surface rupture as well as the seismic and geologic hazards along the Beichuan segment between Leigu Town and Qushan Town, Beichuan County, are analyzed in detail. Results indicate that surface deformation appears as an oblique thrusting with near equal vertical and right-lateral displacements ranged from 2 to 10 m, in which the largest displacement occurred along this segment in the Yingxiu-Beichuan fault. A notable distribution feature of geologic disasters and building damages induced by this earthquake shows strong hanging wall effects across the surface rupture zone:the highest density of landslides, rock falls, debris flows and building damages occurred on the northwest (hanging wall) side of the fault, but few geologic disasters developed on the southeast (foot wall) side of the fault. These effects are caused directly by the asymmetric fault geometry and the stress interaction between the fault motion and free surface of the slopes. Other factors such as material heterogeneity and spatial variation in frictional properties along the fault strike may further affect the rupture and slip patterns of oblique thrust faulting with a right-lateral strike-slip component. From view of disaster mitigation, the geometry and kinematics of surface rupture zone associated with the M_S 8. 0 Wenchuan earthquake also taught a realistic lesson to how to mitigate potential seismic and geologic disasters associated with future great earthquakes in highly populated region through pre-earthquake analysis and evaluation of active faults using remote sensing technique combined with field reconnaissance.
引文
[1] 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 and recurrence intervals of the Longmen Shan active fault zone, and tectonic implications for the mechanism of the May 12 Wenchuan earthquake, 2008, Sichuan, China. Chinese J. Geophys. (in Chinese), 2008,51(4) :1066-1073
[2] 徐锡伟,闻学泽,叶建青等.汶川M_s8． 0地震地表破裂带及其发震构造.地震地质,2008,30(3) :597-629 Xu X W, Wen X Z, Ye J Q, et al. The M_s8． 0 Wenchuan earthquake surface ruptures and its seismogenic structure. Seismology and Geology (in Chinese) , 2008, 30(3) ,597-629
[3] 付碧宏,时丕龙,张之武.四川汶川M_s8． 0大地震地表破裂带的遥感影像解析.地质学报,2008,82(12) :1679-1687 Fu B H, Shi P L, Zhang Z W. Spatial characteristics of the surface rupture produced by the M_s8． 0 Wenchuan Earthquake using high-resolution remote sensing imagery. Acta Geologica Sinica (in Chinese), 2008, 82(12) :1679-1687
[4] 李海兵,付小方,J Van Der Woerd等.汶川地震(M_s8． 0) 地表破裂及其同震右旋斜向逆冲作用.地质学报,2008,82(12) :1623-1643 Fu B H, Shi P L, Zhang Z W. Spatial characteristics of the surface rupture produced by the M_s8． 0 Wenchuan Earthquake using high-resolution remote sensing imagery. Acta Geologica Sinica (in Chinese), 2008, 82(12) :1679-1687
[5] 刘静,张智慧,文力等.汶川8级大地震同震破裂的特殊性及构造意义--多条平行断裂同时活动的反序型逆冲地震事件.地质学报,2008,82(12) :1707-1722 Liu J, Zhang Z H, Wen L, et al. The M_s8． 0 Wenchuan earthquake co-seismic rupture and its tectonic implications-An out of sequence thrusting event with slip partitioned on multiple faults. Acta Geologica Sinica (in Chinese), 2008,82(12) :1707-1722
[6] 马保起,张世民,田勤俭等.汶川8． 0级地震地表破裂带.第四纪研究,2008,28(4) :513-517 Ma B Q, Zhang S M, Tian Q J , et al. The surface rupture of Wenchuan earthquake (M8． 0) . Quaternary Sciences (in Chinese), 2008,28(4) :513-517
[7] Burchfiel B C, Royden L H, Van der Hilst R D, et al. A geological and geophysical context for the Wenchuan earthquake of 12 May 2008, Sichuan, People s Republic of China. GSA Today ,2008, 18, doi:10． 1130/GSATG18A. 1
[8] 许志琴,李化启,侯立炜等.青藏高原东缘龙门山-锦屏山造山带的崛起-大型拆离断层和挤出机制,地质通报,2007,26(10) :1262-127 Xu Z Q, Li H Q, Hou L W, et al. Uplift of the Longmen-Jinping orogenic belt along the eastern margin of the Qinghai-Tibet Plateau: Large-scale detachment faulting and extrusion mechanism. Geological Bulletin of China (in Chinese) , 2007,26(10) :1262-1276
[9] Xu Z Q, Ji S C, Li H B, et al. Uplift of the Longmenshan range and the Wenchuan earthquake. Episodes, 2008,31(3) : 291-301
[10] 刘树根,罗志立,赵锡奎等.龙门山造山带-川西前陆盆地系统形成的动力学模式级模拟研究.石油实验地质,2003,25(5) :432-438． Liu S G, Luo Z L, Zhao X K, et al. Study on the dynamic model and its simulation in the formation of Longmen Mountain-West Sichuan foreland basin system. Petroleum Geology and Experiment (in Chinese), 2003, 25(5) :432-438
[11] Meng Q R, Hu J M, Wang E C, et al. Late Cenozoic denudation by large-magnitude landslides in the eastern edge of Tibetan Plateau. Earth and Planetary Science Letters, 2006, 243:252-267
[12] 王二七,孟庆任.对龙门山中生代和新生代构造演化的讨论.中国科学(D),2008,38(10) :1221-1233 Wang E Q, Meng Q R. Discussion on the Mesozoic and Cenozoic tectonic evolution of the Longmen Shan fault belt. Science in China (Series D) (in Chinese) , 2008,38(10) :1221-1233
[13] Royden L H, Burchfiel B C, King R W, et al. Surface deformation and lower crustal flow in eastern Tibet. Science, 1997,276:788-790
[14] Clark M, Royden L H. Topographic ooze; building the eastern margin of Tibet by lower crustal flow. Geology, 2000, 28:703-706
[15] 邓起东,陈社发,赵小麟.龙门山及其邻区的构造和地震活动及动力学.地震地质,1994,16(4) :389-403 Deng Q D, Chen S F, Zhao X L. Tectonics, seismicity and dynamics of Longmenshan Mountains and its adjacent regions. Seismology and Geology (in Chinese), 1994, 16 (4) :389-403
[16] Burchfiel B C, Chen Z, Liu Y, et al. Tectonics of the Longmen Shan and adjacent regions. International Geological Review, 1995, 37:661-735
[17] 李勇,周荣军,Densemore A L等.青藏高原东缘大陆动力学过程与地质响应.北京:地质出版社,2006． 1-148 Li Y, Zhou R J, Densemore A L, et al. Geodynamic Processes of the Eastern Margin of the Tibetan Plateau and Its Geological Responses. Beijing:Geological Publishing House (in Chinese), 2006． 1-148
[18] Densmore A L, Ellis M A, Li Y, et al. Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau. Tectonics, 2007, 26, doi: 10． 1029/ 2006TC001987．
[19] Chen Z, Burchfiel B C, Liu Y, et al. Global positioning system measurements from of the eastern Tibet an their implications for India/Eurasia intercontinental deformation. J. Geophys. Res. , 2000,105:16215-16227．
[20] Zhang P Z, Shen Z K, Wang M, et al. Continuous deformation of the Tibetan Plateau from global positioning system data. Geology, 2004,32(9) :809-812
[21] 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 between surface ruptures and lithologic characteristics of the Wenchuan M_s8． 0 earthquake. Chinese J. Geophys. (in Chinese), 2009, 52(1) :131-139
[22] 郭华东(主编).汶川地震灾害遥感图集.北京:科学出版社,2008 Guo H D(Editor). Atlas of Remote Sensing for Wenchuan Earthquake Disaster. Beijing: Science Press, 2008
[23] 付碧宏,王萍,孔屏等.四川汶川5． 12大地震同震滑动断层泥的发现及构造意义.岩石学报,2008,24(10) :2237-2243 Fu B H, Wang P, Kong P, et al. Preliminary study of coseismic fault gouge occurred in the slip zone of the Wenchuan M_s8． 0 earthquake and its tectonic implications. Acta Petrologica Sinica (in Chinese),2008,24 (10) :2237-2243
[24] Harp E L, Jibson R W. Landslides triggered by the 1994 Northridge, California earthquake. Bulletin of the Seismological Society of America ,1996 , 86:319-332
[25] Keefer D K. Landslides caused by earthquakes. Bulletin of Geological Society of America, 1984,95:406-421
[26] Khazai B, Sitar N. Evaluation of factors controlling earthquake-induced landslides caused by Chi-Chi earthquake and comparison with the Northridge and Loma Prieta events. Engineering Geology , 2004,71:79-95
[27] Owen L A, Kamp U, Khattak G A, et al. Landslides triggered by the 8 October 2005 Kashmir earthquake. Geomorphology, 2008,94:1-9
[28] Fu B H, Ninomiya Y, Lei, X L. et al. Mapping the active strike-slip fault triggered the 2003 M_s6． 6 Bam, Iran, earthquake with ASTER 3D images. Remote Sensing of Environment, 1004,92:153-157
[29] Yeats R S, Sieh K, Allen C R. The Geology of Earthquakes. New York: Oxford University Press, 1997． 1-568
[30] Wesnousky S G. Displacement and geometrical characteristics of earthquake surface ruptures: issues and implications for seismic-hazard analysis and the process of earthquake rupture. Bulletin of the Seismological Society of America, 2008,98(4) :1609-1632
[31] Brune J N. Shattered rock and precarious rock evidence for strong asymmetry in ground motions during thrust faulting. Bulletin of the Seismological Society of America, 2001,91 (3) :441-447
[32] Ma S. Beroza G C. Rupture dynamics on a bimaterial interface for dipping faults. Bulletin of the Seismological Society of America, 2008, 98(4) :1642-1658
[33] Oglesby D D, Archuleta R J, Nielsen S B. Earthquakes on dipping faults:the effects of broken symmetry. Science, 1998, 280:1055-1059．
[34] 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 the M_s8． 0 Wenchuan earthquake of Sichuan, China. Chinese J. Geophys. (in Chinese), 2008,51(5) :1403-1410
[35] 黄媛,吴建平,张天中等.汶川8． 0级大地震及其余震序列重定位研究.中国科学(D).2008,38(10) :1242-1249 Huang Y, Wu J P, Zhang T Z. et al. Relocation of the M8． 0 Wenchuan earthquake and it aftershock sequence. Science in China (Series D) (in Chinese), 2008, 38(10) :1242-1249
[2] 徐锡伟,闻学泽,叶建青等.汶川M_s8． 0地震地表破裂带及其发震构造.地震地质,2008,30(3) :597-629 Xu X W, Wen X Z, Ye J Q, et al. The M_s8． 0 Wenchuan earthquake surface ruptures and its seismogenic structure. Seismology and Geology (in Chinese) , 2008, 30(3) ,597-629
[3] 付碧宏,时丕龙,张之武.四川汶川M_s8． 0大地震地表破裂带的遥感影像解析.地质学报,2008,82(12) :1679-1687 Fu B H, Shi P L, Zhang Z W. Spatial characteristics of the surface rupture produced by the M_s8． 0 Wenchuan Earthquake using high-resolution remote sensing imagery. Acta Geologica Sinica (in Chinese), 2008, 82(12) :1679-1687
[4] 李海兵,付小方,J Van Der Woerd等.汶川地震(M_s8． 0) 地表破裂及其同震右旋斜向逆冲作用.地质学报,2008,82(12) :1623-1643 Fu B H, Shi P L, Zhang Z W. Spatial characteristics of the surface rupture produced by the M_s8． 0 Wenchuan Earthquake using high-resolution remote sensing imagery. Acta Geologica Sinica (in Chinese), 2008, 82(12) :1679-1687
[5] 刘静,张智慧,文力等.汶川8级大地震同震破裂的特殊性及构造意义--多条平行断裂同时活动的反序型逆冲地震事件.地质学报,2008,82(12) :1707-1722 Liu J, Zhang Z H, Wen L, et al. The M_s8． 0 Wenchuan earthquake co-seismic rupture and its tectonic implications-An out of sequence thrusting event with slip partitioned on multiple faults. Acta Geologica Sinica (in Chinese), 2008,82(12) :1707-1722
[6] 马保起,张世民,田勤俭等.汶川8． 0级地震地表破裂带.第四纪研究,2008,28(4) :513-517 Ma B Q, Zhang S M, Tian Q J , et al. The surface rupture of Wenchuan earthquake (M8． 0) . Quaternary Sciences (in Chinese), 2008,28(4) :513-517
[7] Burchfiel B C, Royden L H, Van der Hilst R D, et al. A geological and geophysical context for the Wenchuan earthquake of 12 May 2008, Sichuan, People s Republic of China. GSA Today ,2008, 18, doi:10． 1130/GSATG18A. 1
[8] 许志琴,李化启,侯立炜等.青藏高原东缘龙门山-锦屏山造山带的崛起-大型拆离断层和挤出机制,地质通报,2007,26(10) :1262-127 Xu Z Q, Li H Q, Hou L W, et al. Uplift of the Longmen-Jinping orogenic belt along the eastern margin of the Qinghai-Tibet Plateau: Large-scale detachment faulting and extrusion mechanism. Geological Bulletin of China (in Chinese) , 2007,26(10) :1262-1276
[9] Xu Z Q, Ji S C, Li H B, et al. Uplift of the Longmenshan range and the Wenchuan earthquake. Episodes, 2008,31(3) : 291-301
[10] 刘树根,罗志立,赵锡奎等.龙门山造山带-川西前陆盆地系统形成的动力学模式级模拟研究.石油实验地质,2003,25(5) :432-438． Liu S G, Luo Z L, Zhao X K, et al. Study on the dynamic model and its simulation in the formation of Longmen Mountain-West Sichuan foreland basin system. Petroleum Geology and Experiment (in Chinese), 2003, 25(5) :432-438
[11] Meng Q R, Hu J M, Wang E C, et al. Late Cenozoic denudation by large-magnitude landslides in the eastern edge of Tibetan Plateau. Earth and Planetary Science Letters, 2006, 243:252-267
[12] 王二七,孟庆任.对龙门山中生代和新生代构造演化的讨论.中国科学(D),2008,38(10) :1221-1233 Wang E Q, Meng Q R. Discussion on the Mesozoic and Cenozoic tectonic evolution of the Longmen Shan fault belt. Science in China (Series D) (in Chinese) , 2008,38(10) :1221-1233
[13] Royden L H, Burchfiel B C, King R W, et al. Surface deformation and lower crustal flow in eastern Tibet. Science, 1997,276:788-790
[14] Clark M, Royden L H. Topographic ooze; building the eastern margin of Tibet by lower crustal flow. Geology, 2000, 28:703-706
[15] 邓起东,陈社发,赵小麟.龙门山及其邻区的构造和地震活动及动力学.地震地质,1994,16(4) :389-403 Deng Q D, Chen S F, Zhao X L. Tectonics, seismicity and dynamics of Longmenshan Mountains and its adjacent regions. Seismology and Geology (in Chinese), 1994, 16 (4) :389-403
[16] Burchfiel B C, Chen Z, Liu Y, et al. Tectonics of the Longmen Shan and adjacent regions. International Geological Review, 1995, 37:661-735
[17] 李勇,周荣军,Densemore A L等.青藏高原东缘大陆动力学过程与地质响应.北京:地质出版社,2006． 1-148 Li Y, Zhou R J, Densemore A L, et al. Geodynamic Processes of the Eastern Margin of the Tibetan Plateau and Its Geological Responses. Beijing:Geological Publishing House (in Chinese), 2006． 1-148
[18] Densmore A L, Ellis M A, Li Y, et al. Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau. Tectonics, 2007, 26, doi: 10． 1029/ 2006TC001987．
[19] Chen Z, Burchfiel B C, Liu Y, et al. Global positioning system measurements from of the eastern Tibet an their implications for India/Eurasia intercontinental deformation. J. Geophys. Res. , 2000,105:16215-16227．
[20] Zhang P Z, Shen Z K, Wang M, et al. Continuous deformation of the Tibetan Plateau from global positioning system data. Geology, 2004,32(9) :809-812
[21] 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 between surface ruptures and lithologic characteristics of the Wenchuan M_s8． 0 earthquake. Chinese J. Geophys. (in Chinese), 2009, 52(1) :131-139
[22] 郭华东(主编).汶川地震灾害遥感图集.北京:科学出版社,2008 Guo H D(Editor). Atlas of Remote Sensing for Wenchuan Earthquake Disaster. Beijing: Science Press, 2008
[23] 付碧宏,王萍,孔屏等.四川汶川5． 12大地震同震滑动断层泥的发现及构造意义.岩石学报,2008,24(10) :2237-2243 Fu B H, Wang P, Kong P, et al. Preliminary study of coseismic fault gouge occurred in the slip zone of the Wenchuan M_s8． 0 earthquake and its tectonic implications. Acta Petrologica Sinica (in Chinese),2008,24 (10) :2237-2243
[24] Harp E L, Jibson R W. Landslides triggered by the 1994 Northridge, California earthquake. Bulletin of the Seismological Society of America ,1996 , 86:319-332
[25] Keefer D K. Landslides caused by earthquakes. Bulletin of Geological Society of America, 1984,95:406-421
[26] Khazai B, Sitar N. Evaluation of factors controlling earthquake-induced landslides caused by Chi-Chi earthquake and comparison with the Northridge and Loma Prieta events. Engineering Geology , 2004,71:79-95
[27] Owen L A, Kamp U, Khattak G A, et al. Landslides triggered by the 8 October 2005 Kashmir earthquake. Geomorphology, 2008,94:1-9
[28] Fu B H, Ninomiya Y, Lei, X L. et al. Mapping the active strike-slip fault triggered the 2003 M_s6． 6 Bam, Iran, earthquake with ASTER 3D images. Remote Sensing of Environment, 1004,92:153-157
[29] Yeats R S, Sieh K, Allen C R. The Geology of Earthquakes. New York: Oxford University Press, 1997． 1-568
[30] Wesnousky S G. Displacement and geometrical characteristics of earthquake surface ruptures: issues and implications for seismic-hazard analysis and the process of earthquake rupture. Bulletin of the Seismological Society of America, 2008,98(4) :1609-1632
[31] Brune J N. Shattered rock and precarious rock evidence for strong asymmetry in ground motions during thrust faulting. Bulletin of the Seismological Society of America, 2001,91 (3) :441-447
[32] Ma S. Beroza G C. Rupture dynamics on a bimaterial interface for dipping faults. Bulletin of the Seismological Society of America, 2008, 98(4) :1642-1658
[33] Oglesby D D, Archuleta R J, Nielsen S B. Earthquakes on dipping faults:the effects of broken symmetry. Science, 1998, 280:1055-1059．
[34] 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 the M_s8． 0 Wenchuan earthquake of Sichuan, China. Chinese J. Geophys. (in Chinese), 2008,51(5) :1403-1410
[35] 黄媛,吴建平,张天中等.汶川8． 0级大地震及其余震序列重定位研究.中国科学(D).2008,38(10) :1242-1249 Huang Y, Wu J P, Zhang T Z. et al. Relocation of the M8． 0 Wenchuan earthquake and it aftershock sequence. Science in China (Series D) (in Chinese), 2008, 38(10) :1242-1249
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