汶川M_S8.0地震断层映秀—南坝段的活动方式、形变特征及其形成机制
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摘要
通过对2008年5月12日发生的汶川8.0级地震的发震构造——中央断裂映秀—南坝段地震地表破裂、地表形变及断裂上余震迁移等特征的详细调查和分析,结果表明:(1)自映秀至南坝,断层活动方式表现为由逆冲逐渐过渡为逆冲-右旋走滑、再到走滑分量与逆冲分量大致相当,同时断层两盘滑动伴有相对弱旋转活动;(2)在断层总体走向NE向、逆冲为主兼右旋走滑活动方式下,局部表现为走向NW向、逆冲为主兼左旋走滑活动方式;(3)地震裂缝与单侧破裂面关系,以及地表重叠缩短形变特征表明,断层活动、应变能释放是在近EW向区域构造应力及NE向局部构造应力综合作用下的结果.依据断层沿线地表裂缝产状的变化,粗略推出映秀至南坝段主应力方向由SEE向NEE方向变化,与前人使用CAP(Cut and Pasate)方法求出的主余震源机制方向基本一致.
According to the surface rupture belts,deformation characteristics,kinematic characteristics and aftershock migration characteristics formed by Wenchuan M_S8.0 earthquake along the Yingxiu-Nanba segment of Central Fault Belt on May 12~(th) 2008,the research result shows.(1) From Yingxiu to Nanba,the faulting mode changes from reverse-thrusting to reversethrusting with right lateral slipping of comparable amplitude,and is accompanied by a weak rotation between the two walls of the fault;(2) On the whole the NE striking fault is dominated by thrusting with right lateral slipping,while locally there is NW striking thrusting with left lateral slipping;(3) The relation between earthquake cracks and the rupture surface,and the deformation characteristics of the overlapping shortening on the earth's surface reveal that the rupture and strain energy release resulted from the combined action of regional tectonic stress in near E-W direction and local tectonic stress in NE direction.Based on the attitude change of surface cracks along the fault,we deduce that the direction of principal stress changes from SEE in Yingxiu to NEE in Nanba,which accords with the focal mechanism solutions of the mainshock and aftershocks determined with the CAP (Cut and Pasate) method.
According to the surface rupture belts,deformation characteristics,kinematic characteristics and aftershock migration characteristics formed by Wenchuan M_S8.0 earthquake along the Yingxiu-Nanba segment of Central Fault Belt on May 12~(th) 2008,the research result shows.(1) From Yingxiu to Nanba,the faulting mode changes from reverse-thrusting to reversethrusting with right lateral slipping of comparable amplitude,and is accompanied by a weak rotation between the two walls of the fault;(2) On the whole the NE striking fault is dominated by thrusting with right lateral slipping,while locally there is NW striking thrusting with left lateral slipping;(3) The relation between earthquake cracks and the rupture surface,and the deformation characteristics of the overlapping shortening on the earth's surface reveal that the rupture and strain energy release resulted from the combined action of regional tectonic stress in near E-W direction and local tectonic stress in NE direction.Based on the attitude change of surface cracks along the fault,we deduce that the direction of principal stress changes from SEE in Yingxiu to NEE in Nanba,which accords with the focal mechanism solutions of the mainshock and aftershocks determined with the CAP (Cut and Pasate) method.
引文
1) 万天丰.构造应力场(初稿).北京:武汉地质学院北京研究生部,1983． 46
[1] 徐锡伟,闻学泽,郑荣章等.川滇地区活动块体最新构造变动样式及其动力来源.中国科学(D辑),2003,33(增刊):151～162 Xu X W, Wen X Z, Zheng R Z, et al. The newest way and force source of active block in Sichuan-Yuan area. Science in China (SeriesD) (in Chinese), 2003,33(Suppl. ), 151～162
[2] 张岳桥,杨农,陈文等.中国东西部地貌边界带晚新生代构造变形历史与青藏高原东缘隆升过程初步研究.地学前缘,2003,10(4) :599～612 Zhang Y Q, Yang N, Chen W , et al. Late Cenozoic tectonic deformation history of the east-west geomorphological boundary zone of China and uplift process of the eastern margin of the Tibetan plateau. Earth. Science Frontiers (in Chinese), 2003 ,10(4) : 599 ～ 612
[3] 卢海峰,何仲太,赵俊香等.元谋断裂晚第四纪活动性定量分析.地球科学-中国地质大学学报,2008,33(6) :852～860 Lu H F, He Z T, Zhao J X, et al. Quantitative analysis on activity of the Yuanmou Fault in Late Quaternary. Earth Science-Journal of China University of Geosciences C in Chinese) ,2008,33(6) :852～860
[4] 陈运泰,许力生,张勇等.2008年5月12日汶川特大地震震源特性分析报告.http://www.csi.ac.cn/sichuan/chenyuntai.pdf(2008-05-25) Chen Y T, Xu L S, Zhang Y, et al. Report on the Wenchuan larger earthquake source of May 12,2008． http://www. csi. ac. cn/sichuan/chenyuntai. pdf(2008-05-25)
[5] 邓起东.关于四川汶川8． 0级地震的思考.地震地质,2008,30(4) :811～827
Deng Q D. Some thoughts on the M_s8． 0 Wenchuan,Sichuan. Seismology and Geology (in Chinese), 2008,30(4) :811～827
[ 6 ] Li Xiaojun, Zhou Zhenghua, Yu Haiyin, et al. Strong motion observations and recordings from the great Wenchuan earthquake. Earthquake Engineering and Engineering Vibration, 2008, 7(3) : 235 ～ 246． doi: 10． 1007/s11803-008-0892-x
[7] 田勤俭,张立人,郝平等.昆仑山口西8． 1级地震地表破裂参数相互关系的新认识.地震地质,2005,27(1) :20～30 Tian Q J, Zhang L R, Hao P, et al. New insight into the surface rupture parameters of the Kunlunshan M_s8． 1 earthquake. Seismology and Geology (in Chinese) , 2005 , 27(1) :20～30
[8] 许志琴.地壳形变与显微构造.北京:地质出版社,1984 Xu Z Q. Crustal Deformation and Microstructure (in Chinese). Beijing: Geological Publishing House, 1984
[9] 崔作舟.龙门山断裂带的特征及力学机制.地质力学与地壳运动-地质力学开放研究实验室1991～1992年报.北京:地震出版社,1994． 235～245
[10] 卢海峰,马保起,刘光勋.甘肃文县北部北东东向断裂带新构造活动特征.地震研究,2006,29(2) :143～146
Lu H F, Ma B Q, Liu G X. Characteristics of the neotectonic movement of the NEE-striking fault belt north of Wen County, Gansu. Journal of Seismological Research (in Chinese) ,2006 ,29(2) : 143～146
[11] 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M_s8． 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 moment tensor inversion with applications to the 2008 Wenchuan M_s8． 0 earthquake sequence. Acta Seismologica Sinica (in Chinese) ,2008,30(4) :329～339
[12] 蒋长胜,郑 勇.中国大陆部分5级以上地震震源机制解.http://www.cea-igp.ac.cn/共享资源/中国大陆部分5级以上地震震源机制解.htm
[13] 谢富仁,祝景忠,粱海庆等.中国西南地区现代构造应力场基本特征.地震学报,1993,15(4) :407～417
Xie F R, Zhu J Z, Liang H Q, et al. The basic characteristics of recent tectonic stress field in southwest region of China. Acta Seismologica Sinica (in Chinese),1993,15(4) :407～417
[14] 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
[15] 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 of the source mechanism of the 2008 great Wenchuan earthquake. Chinese J. Geophys. (in Chinese) , 2009 ,52( 2) :379 ～ 389
[16] 付碧宏,时丕龙,王萍等.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.地球物理学报,2009,52(2) :485～495 Fu B H, Shi P L, Wang P, et al. Geometry and kinematics of the 2008 Wenchuan earthquake surface ruptures around the Qushan Town of Beichuan County, Sichuan: Implications for mitigation of seismic and geologic disasters. Chinese J.Geophys. (in Chinese), 2009 ,52(2) :485 ～ 495
[17] 吴锡浩,王富葆,安芷生等.晚新生代青藏高原窿升的阶段和高度.黄土·第四纪地质·全球变化(第三集).北京:科学出版社,1992 Wu X H, Wang F B, An Z S, et al. Phase and Altitude of Tibet Plateau Uplift in Late Cenozoic. Loess · Quaternary Geology· Global Change (the third) (in Chinese). Beijing: Science Press, 1992
[1] 徐锡伟,闻学泽,郑荣章等.川滇地区活动块体最新构造变动样式及其动力来源.中国科学(D辑),2003,33(增刊):151～162 Xu X W, Wen X Z, Zheng R Z, et al. The newest way and force source of active block in Sichuan-Yuan area. Science in China (SeriesD) (in Chinese), 2003,33(Suppl. ), 151～162
[2] 张岳桥,杨农,陈文等.中国东西部地貌边界带晚新生代构造变形历史与青藏高原东缘隆升过程初步研究.地学前缘,2003,10(4) :599～612 Zhang Y Q, Yang N, Chen W , et al. Late Cenozoic tectonic deformation history of the east-west geomorphological boundary zone of China and uplift process of the eastern margin of the Tibetan plateau. Earth. Science Frontiers (in Chinese), 2003 ,10(4) : 599 ～ 612
[3] 卢海峰,何仲太,赵俊香等.元谋断裂晚第四纪活动性定量分析.地球科学-中国地质大学学报,2008,33(6) :852～860 Lu H F, He Z T, Zhao J X, et al. Quantitative analysis on activity of the Yuanmou Fault in Late Quaternary. Earth Science-Journal of China University of Geosciences C in Chinese) ,2008,33(6) :852～860
[4] 陈运泰,许力生,张勇等.2008年5月12日汶川特大地震震源特性分析报告.http://www.csi.ac.cn/sichuan/chenyuntai.pdf(2008-05-25) Chen Y T, Xu L S, Zhang Y, et al. Report on the Wenchuan larger earthquake source of May 12,2008． http://www. csi. ac. cn/sichuan/chenyuntai. pdf(2008-05-25)
[5] 邓起东.关于四川汶川8． 0级地震的思考.地震地质,2008,30(4) :811～827
Deng Q D. Some thoughts on the M_s8． 0 Wenchuan,Sichuan. Seismology and Geology (in Chinese), 2008,30(4) :811～827
[ 6 ] Li Xiaojun, Zhou Zhenghua, Yu Haiyin, et al. Strong motion observations and recordings from the great Wenchuan earthquake. Earthquake Engineering and Engineering Vibration, 2008, 7(3) : 235 ～ 246． doi: 10． 1007/s11803-008-0892-x
[7] 田勤俭,张立人,郝平等.昆仑山口西8． 1级地震地表破裂参数相互关系的新认识.地震地质,2005,27(1) :20～30 Tian Q J, Zhang L R, Hao P, et al. New insight into the surface rupture parameters of the Kunlunshan M_s8． 1 earthquake. Seismology and Geology (in Chinese) , 2005 , 27(1) :20～30
[8] 许志琴.地壳形变与显微构造.北京:地质出版社,1984 Xu Z Q. Crustal Deformation and Microstructure (in Chinese). Beijing: Geological Publishing House, 1984
[9] 崔作舟.龙门山断裂带的特征及力学机制.地质力学与地壳运动-地质力学开放研究实验室1991～1992年报.北京:地震出版社,1994． 235～245
[10] 卢海峰,马保起,刘光勋.甘肃文县北部北东东向断裂带新构造活动特征.地震研究,2006,29(2) :143～146
Lu H F, Ma B Q, Liu G X. Characteristics of the neotectonic movement of the NEE-striking fault belt north of Wen County, Gansu. Journal of Seismological Research (in Chinese) ,2006 ,29(2) : 143～146
[11] 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M_s8． 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 moment tensor inversion with applications to the 2008 Wenchuan M_s8． 0 earthquake sequence. Acta Seismologica Sinica (in Chinese) ,2008,30(4) :329～339
[12] 蒋长胜,郑 勇.中国大陆部分5级以上地震震源机制解.http://www.cea-igp.ac.cn/共享资源/中国大陆部分5级以上地震震源机制解.htm
[13] 谢富仁,祝景忠,粱海庆等.中国西南地区现代构造应力场基本特征.地震学报,1993,15(4) :407～417
Xie F R, Zhu J Z, Liang H Q, et al. The basic characteristics of recent tectonic stress field in southwest region of China. Acta Seismologica Sinica (in Chinese),1993,15(4) :407～417
[14] 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
[15] 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 of the source mechanism of the 2008 great Wenchuan earthquake. Chinese J. Geophys. (in Chinese) , 2009 ,52( 2) :379 ～ 389
[16] 付碧宏,时丕龙,王萍等.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.地球物理学报,2009,52(2) :485～495 Fu B H, Shi P L, Wang P, et al. Geometry and kinematics of the 2008 Wenchuan earthquake surface ruptures around the Qushan Town of Beichuan County, Sichuan: Implications for mitigation of seismic and geologic disasters. Chinese J.Geophys. (in Chinese), 2009 ,52(2) :485 ～ 495
[17] 吴锡浩,王富葆,安芷生等.晚新生代青藏高原窿升的阶段和高度.黄土·第四纪地质·全球变化(第三集).北京:科学出版社,1992 Wu X H, Wang F B, An Z S, et al. Phase and Altitude of Tibet Plateau Uplift in Late Cenozoic. Loess · Quaternary Geology· Global Change (the third) (in Chinese). Beijing: Science Press, 1992
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