2008年汶川M_S 8.0地震北川以北段地表破裂变形的主要样式
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摘要
2008年5月12日发生的汶川地震是由青藏高原东部龙门山断裂的活动所导致。震后的调查表明,北川县城以北的断裂段破裂了约90km。在北川县城以北,不同地点沿地震地表破裂所展现的地表变形差异很大,可能反映了断裂附近地表特性的变化。文章主要从5个典型地点来阐述5种代表性的地表变形模式。前两个地点,在北川县城以北几公里,反映了近地表基岩中的一种变形和从基岩向松散堆积物过渡区的一种变形模式。与此两种断裂陡坎变形不同,中间的两个点则阐述了褶皱陡坎,它们反映了2008年地震中断裂断错在地表以下终止的不同情形。最后一个点位于汶川地震地表破裂的北端,可能代表了当地表破裂结束时地表变形的模式。在北川以北段地表破裂上典型地点的详细测量的基础上,通过归纳野外获得的地表变形资料,构建出汶川地震地表破裂北川以北段的基本变形模型。
The May 12,2008,M_S 8.0 Wenchuan Earthquake was the result of the activity of the Longmenshan Fault,a thrust fault zone in the eastern margin of the Tibet Plateau.Field investigation after earthquake discovers that the Northern Yingxiu-Beichuan Fault ruptured the surface about 90km north to Beichuan City during the earthquake. The deformation shows greatly pattern differences along the rupture,which may reflect the varied nature of surface breaking.In this paper,we present deformation patterns observed from five representative sites.The first two sites (the North Beichuan City site and the Shilinzi Village site)are several kilometers away from each,displaying a pattern of deformation in bedrocks and a pattern of deformation at the transition from bedrock to unconsolidated cover.The central two sites(the Fenghuang Village site and the Mowan Village site)demonstrate folding scarps which may indicate slipping depth during earthquake.The final site(the Pingxi Village site)is at the northern termination of the Wenchuan Earthquake surface rupture,which may represent a pattern when the fault terminates rupturing the ground surface.Based on field survey on these sites we constructed schematically five deformation models,which are Simple thrust scarp,Hanging wall collapsed fault scarp,Multiple thrust scarps,Warping scarp, and Monoclinal folding scarp,along the Wenchuan Earthquake surface rupture.
The May 12,2008,M_S 8.0 Wenchuan Earthquake was the result of the activity of the Longmenshan Fault,a thrust fault zone in the eastern margin of the Tibet Plateau.Field investigation after earthquake discovers that the Northern Yingxiu-Beichuan Fault ruptured the surface about 90km north to Beichuan City during the earthquake. The deformation shows greatly pattern differences along the rupture,which may reflect the varied nature of surface breaking.In this paper,we present deformation patterns observed from five representative sites.The first two sites (the North Beichuan City site and the Shilinzi Village site)are several kilometers away from each,displaying a pattern of deformation in bedrocks and a pattern of deformation at the transition from bedrock to unconsolidated cover.The central two sites(the Fenghuang Village site and the Mowan Village site)demonstrate folding scarps which may indicate slipping depth during earthquake.The final site(the Pingxi Village site)is at the northern termination of the Wenchuan Earthquake surface rupture,which may represent a pattern when the fault terminates rupturing the ground surface.Based on field survey on these sites we constructed schematically five deformation models,which are Simple thrust scarp,Hanging wall collapsed fault scarp,Multiple thrust scarps,Warping scarp, and Monoclinal folding scarp,along the Wenchuan Earthquake surface rupture.
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 Peizhen, X u Xiwei, Wen Xueze 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 Journal of Geophysics,2008, 51(4) : 1066-1073
2 徐锡伟,闻学泽,叶建青等.汶川Ms8 0地震地表破裂带及其发震构造地震地质,2008,30(3) :597-629 Xu Xiwei, Wen Xueze, Ye Jianqing et al. The Ms8． 0 Wenchuan earthquake surface ruptures and its seismogenic structure. Seismology and Geology,2008,30(3) :597-629
3 李传友,叶 建青,谢富仁等.汶川Ms8． 0地震地表破裂带北川以北段的基本特征.地震地质,2008,30(3) :683-696 Li Chuanyou, Ye Jianqing, Xie Furen et al. Characteristics of the surface rupture zone of the segment north to Beichuan of the Ms8． 0 Wenchuan earthquake, China. Seismology and Geology, 2008, 30(3) : 683-696
4 冉勇康,史翔,王虎等.汶川M8． 0地震最大地表同震垂直位移及其地表变形样式.科学通报,2009(待刊) Ran Yongkang, Shi Xiang, Wang Hu et al. The Maximum vertical displacement of Wenchuan M_S8． 0 earthquake and its deformation pattern. Chinese Science Bulletin,2009( in press)
5 Philip H, Meghraoui M. Structural analysis and interpretation of the surface deformations of the El Asnam earthquake of October 10, 1980． Tectonics,1983,2(1 ) : 17-49
6 Stein R S, King G C P. Seixmic potential revealed by surface folding: 1983 Coalinga, California earthquake. Science, 1984,224 : 869-872
7 Philip H, Rogozhin E,Cisternas A et al. The Armenian earthquake of 1998 December 7 : Faulting and folding, neotectonics and paleoseismicity. Geophys Journal International, 1992,110 : 141-158
8 Kelson K I, Kang K H, Page W D et al. Representative style of deformation along the Chelungpu fault from the 1999 Chi-Chi (Taiwan) earthquake: Geomorphic characteristics and response of man-made structures. Bulletin of the Seismological Society of America ,2001,91 : 930-952
9 Angelier J, Lee J C, Hu J C et al. Three-dimensional deformation along the rupture trace of the September 21st, 1999, Taiwan earthquake: A case study in the Kuangfu school. Journal of Structural Geology,2003, 25: 351-370
10 England P, Houseman G. Finite strain calculations of continental deformation 2． Comparison with the India-Asia collision zone. Journal of Geophysical Research, 1986,91 (B3) : 3664-3676
11 Avouac J P, Tapponnier P. Kinematic model of active deformation in Central Asia. Geophysical Research Letters, 1993,20: 895-898
12 Burchfiel B, Chen Z, Liu Yet al. Tectonics of the Longmen Shan and adjacent regions. International Geology Review, 1995, 37: 661-735
13 King R W, Shen Feng,Burchfiel B C et al. Geodetic measurement of crustal motion in South West China. Geology, 1997,25 : 179-182
14 Chen Z, Burchfiel B C, Liu Y et al. Global positioning system measurements from Eastern Tibet and their implications for India/Eurasia intercontinental deformation. Journal of Geophysical Research, 2000,105(B7) : 16215-16227
15 Clark M K, Royden L H. Topographic ooze: Building the eastern margin of Tibet by lower crustal flow. Geology,2000,28:703-706
16 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
17 Dirks P H G M, Wilson C J L,Chen S F et al. Tectonic evolution of the NE margin of the Tibetan Plateau: Evidence from the Central Longmen Mountains,Sichuan Province,China. Journal of South East Asian Earth Sciences, 1994,9:181-192
18 Chen S F, Wilson C J L. Emplacement of the Longmen Shan thrustnappe belt along the eastern margin of the Tibetan Plateau. Journal of Structural Geology, 1996,18 : 413-430
19 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 Qidong, Chen Shefa, Zhao Xiaolin. Tectonics, seismisity and dynamics of Longmenshan Mountains and its adjacent regions. Seismology and Geology, 1994,16 (4) : 389-403
20 Densmore A L, Ellis M A, Li Yong et al. Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau. Tectonics, 2007, 26: TC4005, doi: 10． 1029/ 2006TC001987
21 Chen Shefa, Wilson C J L, Deng Qidong et al. Active faulting and block movement associated with large earthquakes in the Min Shan and Longmen Mountains,North Eastern Tibetan plateau. Journal of Geophysical Research, 1994,99 ( B 12 ) : 24025-24038
22 Kirby E, Whipple K X,Burchfiel B C et al. Neotectonics of the Min Shan, China: Implications for mechanisms driving Quaternary deformation along the eastern margin of the Tibetan Plateau. Geological Society of America Bulletin, 2000,112 : 375-393
23 郑文俊,李传友,王伟涛等.汶川8． 0级地震陡坎(北川以北段)探槽的记录特征.地震地质,2008,30(3) :697-709 Zheng Wenjun, Li Chuanyou, Wang Weitao et al. Trench logs of earthquake scarp of the M_S8． 0 Wenchuan Earthquake in the segment north of Beichuan. Seismology and Geology,2008,30 ( 3 ) :697-709
2 徐锡伟,闻学泽,叶建青等.汶川Ms8 0地震地表破裂带及其发震构造地震地质,2008,30(3) :597-629 Xu Xiwei, Wen Xueze, Ye Jianqing et al. The Ms8． 0 Wenchuan earthquake surface ruptures and its seismogenic structure. Seismology and Geology,2008,30(3) :597-629
3 李传友,叶 建青,谢富仁等.汶川Ms8． 0地震地表破裂带北川以北段的基本特征.地震地质,2008,30(3) :683-696 Li Chuanyou, Ye Jianqing, Xie Furen et al. Characteristics of the surface rupture zone of the segment north to Beichuan of the Ms8． 0 Wenchuan earthquake, China. Seismology and Geology, 2008, 30(3) : 683-696
4 冉勇康,史翔,王虎等.汶川M8． 0地震最大地表同震垂直位移及其地表变形样式.科学通报,2009(待刊) Ran Yongkang, Shi Xiang, Wang Hu et al. The Maximum vertical displacement of Wenchuan M_S8． 0 earthquake and its deformation pattern. Chinese Science Bulletin,2009( in press)
5 Philip H, Meghraoui M. Structural analysis and interpretation of the surface deformations of the El Asnam earthquake of October 10, 1980． Tectonics,1983,2(1 ) : 17-49
6 Stein R S, King G C P. Seixmic potential revealed by surface folding: 1983 Coalinga, California earthquake. Science, 1984,224 : 869-872
7 Philip H, Rogozhin E,Cisternas A et al. The Armenian earthquake of 1998 December 7 : Faulting and folding, neotectonics and paleoseismicity. Geophys Journal International, 1992,110 : 141-158
8 Kelson K I, Kang K H, Page W D et al. Representative style of deformation along the Chelungpu fault from the 1999 Chi-Chi (Taiwan) earthquake: Geomorphic characteristics and response of man-made structures. Bulletin of the Seismological Society of America ,2001,91 : 930-952
9 Angelier J, Lee J C, Hu J C et al. Three-dimensional deformation along the rupture trace of the September 21st, 1999, Taiwan earthquake: A case study in the Kuangfu school. Journal of Structural Geology,2003, 25: 351-370
10 England P, Houseman G. Finite strain calculations of continental deformation 2． Comparison with the India-Asia collision zone. Journal of Geophysical Research, 1986,91 (B3) : 3664-3676
11 Avouac J P, Tapponnier P. Kinematic model of active deformation in Central Asia. Geophysical Research Letters, 1993,20: 895-898
12 Burchfiel B, Chen Z, Liu Yet al. Tectonics of the Longmen Shan and adjacent regions. International Geology Review, 1995, 37: 661-735
13 King R W, Shen Feng,Burchfiel B C et al. Geodetic measurement of crustal motion in South West China. Geology, 1997,25 : 179-182
14 Chen Z, Burchfiel B C, Liu Y et al. Global positioning system measurements from Eastern Tibet and their implications for India/Eurasia intercontinental deformation. Journal of Geophysical Research, 2000,105(B7) : 16215-16227
15 Clark M K, Royden L H. Topographic ooze: Building the eastern margin of Tibet by lower crustal flow. Geology,2000,28:703-706
16 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
17 Dirks P H G M, Wilson C J L,Chen S F et al. Tectonic evolution of the NE margin of the Tibetan Plateau: Evidence from the Central Longmen Mountains,Sichuan Province,China. Journal of South East Asian Earth Sciences, 1994,9:181-192
18 Chen S F, Wilson C J L. Emplacement of the Longmen Shan thrustnappe belt along the eastern margin of the Tibetan Plateau. Journal of Structural Geology, 1996,18 : 413-430
19 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 Qidong, Chen Shefa, Zhao Xiaolin. Tectonics, seismisity and dynamics of Longmenshan Mountains and its adjacent regions. Seismology and Geology, 1994,16 (4) : 389-403
20 Densmore A L, Ellis M A, Li Yong et al. Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau. Tectonics, 2007, 26: TC4005, doi: 10． 1029/ 2006TC001987
21 Chen Shefa, Wilson C J L, Deng Qidong et al. Active faulting and block movement associated with large earthquakes in the Min Shan and Longmen Mountains,North Eastern Tibetan plateau. Journal of Geophysical Research, 1994,99 ( B 12 ) : 24025-24038
22 Kirby E, Whipple K X,Burchfiel B C et al. Neotectonics of the Min Shan, China: Implications for mechanisms driving Quaternary deformation along the eastern margin of the Tibetan Plateau. Geological Society of America Bulletin, 2000,112 : 375-393
23 郑文俊,李传友,王伟涛等.汶川8． 0级地震陡坎(北川以北段)探槽的记录特征.地震地质,2008,30(3) :697-709 Zheng Wenjun, Li Chuanyou, Wang Weitao et al. Trench logs of earthquake scarp of the M_S8． 0 Wenchuan Earthquake in the segment north of Beichuan. Seismology and Geology,2008,30 ( 3 ) :697-709
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