从两个地表破裂点的几何学与运动学特征分析汶川地震的破裂方式
|
摘要
汶川MS8.0地震的地表破裂出现在中央和前山2条断裂上,分别形成了235km和72km长的地震地表破裂带,而且地表破裂表现出复杂的几何学和运动学特征。文中选取了中央断裂上虹口乡桐麻坎和擂鼓镇石岩村2个地表破裂点,通过几何学与运动学特征分析其地表破裂方式。桐麻坎的白沙河河床上4条右阶斜列的主破裂西南侧发育了一条反冲断层坎,精细地形测量反映出了破裂带内的断块特征与破裂过程中的地表掀斜;擂鼓镇石岩村逆冲破裂前缘的2条次级断层形成叠瓦式结构,地貌上表现为挠曲和其上部的地震鼓包。该两点地表破裂的几何学、运动学特征分析表明,本次地震在龙门山中央断裂上的破裂方式以逆冲为主,兼有右旋走滑。这一结果与美国地质调查局、哈佛大学和中国地震台网中心提供的震源机制解基本一致。此外,桐麻坎和石岩村横切破裂带的地形剖面显示出不同的地表掀斜方向,这种不一致主要由于前者位于断裂挠曲后缘,后者位于断裂挠曲前缘。
Surface ruptures of the MS 8.0 Wenchuan earthquake are distributed mainly on the Longmenshan central fault and front-range fault,extending 235km and 72km,respectively.The ruptures exhibit complicated characters in geometry and kinematics.On the riverbed of Baisha river,a backthrust scarp was formed in the southwest of the major fault that comprises four right-step sub-faults,and precise topographical measurement shows a kinematic character of fault block and surface tilting in the rupture process;In Shiyan village,the master fault and the secondary fault formed an imbricate structure,and show as flexures and earthquake swells on ground surface.We analyzed the ruptures at Tongmakan village and Shiyan village,both locating on the central fault,by geometry and kinematics,and the results indicate that the earthquake rupturing along the central fault is mainly characterized by thrusting associated with right-lateral strike-slipping.This result is consistent with the focal-mechanism solutions which are promulgated by U.S.Geological Survey,Harvard University and China Earthquake Networks Center.In addition,the profiles of Tongmakan and Shiyan display different tilting directions,and the reason is that the former locates at the trailing edge of the fault,while the latter in the leading edge of fault.
Surface ruptures of the MS 8.0 Wenchuan earthquake are distributed mainly on the Longmenshan central fault and front-range fault,extending 235km and 72km,respectively.The ruptures exhibit complicated characters in geometry and kinematics.On the riverbed of Baisha river,a backthrust scarp was formed in the southwest of the major fault that comprises four right-step sub-faults,and precise topographical measurement shows a kinematic character of fault block and surface tilting in the rupture process;In Shiyan village,the master fault and the secondary fault formed an imbricate structure,and show as flexures and earthquake swells on ground surface.We analyzed the ruptures at Tongmakan village and Shiyan village,both locating on the central fault,by geometry and kinematics,and the results indicate that the earthquake rupturing along the central fault is mainly characterized by thrusting associated with right-lateral strike-slipping.This result is consistent with the focal-mechanism solutions which are promulgated by U.S.Geological Survey,Harvard University and China Earthquake Networks Center.In addition,the profiles of Tongmakan and Shiyan display different tilting directions,and the reason is that the former locates at the trailing edge of the fault,while the latter in the leading edge of fault.
引文
陈桂华,徐锡伟,郑荣章,等.2008.2008年汶川MS8.0地震地表破裂变形定量分析[J].地震地质,30(3):723—738.CHEN Gui-hua,XU Xi-wei,ZHENG Rong-zhang,et al.2008.Quantitative analysis of the co-seismic surface rupture ofthe2008Wenchuan earthquake,Sichuan,China along the Beichuan-Yingxiu Fault[J].Seismology and Geology,30(3):723—738(in Chinese).
邓起东,陈社发,赵小麟.1994.龙门山及其邻区的构造和地震活动及动力学[J].地震地质,16(4):389—403.DENG Qi-dong,CHEN She-fa,ZHAO Xiao-lin.1994.Tectonics,seismicity and dynamics of Longmenshan Mountainsand its adjacent regions[J].Seismology and Geology,16(4):389—403(in Chinese).
冯先岳,陈杰,李军,等.1993.霍尔果斯活动构造的断裂扩展褶皱作用[J].内陆地震,7(4):335—343.FENG Xian-yue,CHEN Jie,LI Jun,et al.1993.The fault-propagation folding of Horgos active structure[J].InlandEarthquake,7(4):335—343(in Chinese).
何宏林,孙昭民,王世元,等.2008a.汶川MS8.0地震地表破裂带[J].地震地质,30(2):359—361.HE Hong-lin,SUN Zhao-min,WANG Shi-yuan,et al.2008a.Rupture of theMS8.0Wenchuan earthquake[J].Seis-mology and Geology,30(2):359—361(in Chinese).
何宏林,孙昭民,魏占玉,等.2008b.汶川MS8.0地震地表破裂带白沙河段破裂及其位移特征[J].地震地质,30(3):658—671.HE Hong-lin,SUN Zhao-min,WEI Zhan-yu,et al.2008b.Rupture of theMS8.0Wenchuan earthquake along Baisha-he River[J].Seismology and Geology,30(3):658—671(in Chinese).
候康明.1998.1927年古浪8级大地震地表破裂特征及形成机制[J].地震地质,20(1):19—26.HOU Kang-ming.1998.Characteristics of ground ruptures caused by1927GulangM8earthquake and their causativemechanisms[J].Seismology and Geology,20(1):19—26(in Chinese).
李传友,宋方敏,冉勇康.2004.龙门山断裂带北段晚第四纪活动性讨论[J].地震地质,26(2):248—258.LI Chuan-you,SONG Fang-min,RAN Yong-kang.2004.Late Quaternary activity and age constraint of the northernLongmenshan Fault zone[J].Seismology and Geology,26(2):248—258(in Chinese).
李勇,周荣军,Densmore A L,et al.2006.青藏高原东缘龙门山晚新生代走滑-逆冲作用的地貌标志[J].第四纪研究,26(1):40—51.LI Yong,ZHOU Rong-jun,Densmore A L,et al.2006.Geomorphic evidence for the late Cenozoic strike-slipping andthrusting in Longmen Mountains at the eastern margin of the Tibetan plateau[J].Quaternary Sciences,26(1):40—51(in Chinese).
唐荣昌,韩渭宾主编.1993.四川活动断裂与地震[M].北京:地震出版社.TANG Rong-chang,HANWei-bin(eds).1993.Active Faults and Earthquakes in Sichuan Province[M].SeismologicalPress,Beijing(in Chinese).
万波,高常波,郑双成.2004.地震地表破裂发育特点及环境条件分析[J].东北地震研究,20(1):1—8.WAN Bo,GAO Chang-bo,ZHENG Shuang-cheng.2004.Features and circumstances for surface seismic ruptures[J].Seismological Research of Northeast China,20(1):1—8(in Chinese).
徐锡伟,闻学泽,叶建青,等.2008.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,30(3):597—629.XU Xi-wei,WEN Xue-ze,YE Jian-qing,et al.2008.TheMS8.0Wenchuan earthquake surface rupture and its seis-mogenic structure[J].Seismology and Geology,30(3):597—629(in Chinese).
张培震,邓起东,徐锡伟,等.1994.盲断裂、褶皱地震与新疆1906年玛纳斯地震[J].地震地质,16(3):193—204.ZHANG Pei-zhen,DENG Qi-dong,XU Xi-wei,et al.1994.Blind thrust,foldding earthquake,and the1906Manasearthquake,Xinjiang[J].Seismology and Geology,16(3):193—204(in Chinese).
中国地震信息网.2008.四川汶川县MS8.0地震参数[R].http://www.csi.ac.cn/sichuan/sichuan080512_csl.htm.China Seismic Information Net.2008.Seismological parameters for theMS8.0Wenchuan earthquake,Sichuan[R].http://www.csi.ac.cn/sichuan/sichuan080512_csl.htm(in Chinese).
Densmore AL,Eills MA,Li Y,et al.2007.Active tectonics of the Beichuan and Pengguan Faults at the eastern marginof the Tibetan Plateau[J].Tectonics,26.doi:10.1029/2006TC001987.
Jones L E,Helmberger D V.1998.Earthquake source parameters and fault kinematic in the eastern California shearzone[J].Bull Seism Soc Am,88(6):1337—1352.
邓起东,陈社发,赵小麟.1994.龙门山及其邻区的构造和地震活动及动力学[J].地震地质,16(4):389—403.DENG Qi-dong,CHEN She-fa,ZHAO Xiao-lin.1994.Tectonics,seismicity and dynamics of Longmenshan Mountainsand its adjacent regions[J].Seismology and Geology,16(4):389—403(in Chinese).
冯先岳,陈杰,李军,等.1993.霍尔果斯活动构造的断裂扩展褶皱作用[J].内陆地震,7(4):335—343.FENG Xian-yue,CHEN Jie,LI Jun,et al.1993.The fault-propagation folding of Horgos active structure[J].InlandEarthquake,7(4):335—343(in Chinese).
何宏林,孙昭民,王世元,等.2008a.汶川MS8.0地震地表破裂带[J].地震地质,30(2):359—361.HE Hong-lin,SUN Zhao-min,WANG Shi-yuan,et al.2008a.Rupture of theMS8.0Wenchuan earthquake[J].Seis-mology and Geology,30(2):359—361(in Chinese).
何宏林,孙昭民,魏占玉,等.2008b.汶川MS8.0地震地表破裂带白沙河段破裂及其位移特征[J].地震地质,30(3):658—671.HE Hong-lin,SUN Zhao-min,WEI Zhan-yu,et al.2008b.Rupture of theMS8.0Wenchuan earthquake along Baisha-he River[J].Seismology and Geology,30(3):658—671(in Chinese).
候康明.1998.1927年古浪8级大地震地表破裂特征及形成机制[J].地震地质,20(1):19—26.HOU Kang-ming.1998.Characteristics of ground ruptures caused by1927GulangM8earthquake and their causativemechanisms[J].Seismology and Geology,20(1):19—26(in Chinese).
李传友,宋方敏,冉勇康.2004.龙门山断裂带北段晚第四纪活动性讨论[J].地震地质,26(2):248—258.LI Chuan-you,SONG Fang-min,RAN Yong-kang.2004.Late Quaternary activity and age constraint of the northernLongmenshan Fault zone[J].Seismology and Geology,26(2):248—258(in Chinese).
李勇,周荣军,Densmore A L,et al.2006.青藏高原东缘龙门山晚新生代走滑-逆冲作用的地貌标志[J].第四纪研究,26(1):40—51.LI Yong,ZHOU Rong-jun,Densmore A L,et al.2006.Geomorphic evidence for the late Cenozoic strike-slipping andthrusting in Longmen Mountains at the eastern margin of the Tibetan plateau[J].Quaternary Sciences,26(1):40—51(in Chinese).
唐荣昌,韩渭宾主编.1993.四川活动断裂与地震[M].北京:地震出版社.TANG Rong-chang,HANWei-bin(eds).1993.Active Faults and Earthquakes in Sichuan Province[M].SeismologicalPress,Beijing(in Chinese).
万波,高常波,郑双成.2004.地震地表破裂发育特点及环境条件分析[J].东北地震研究,20(1):1—8.WAN Bo,GAO Chang-bo,ZHENG Shuang-cheng.2004.Features and circumstances for surface seismic ruptures[J].Seismological Research of Northeast China,20(1):1—8(in Chinese).
徐锡伟,闻学泽,叶建青,等.2008.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,30(3):597—629.XU Xi-wei,WEN Xue-ze,YE Jian-qing,et al.2008.TheMS8.0Wenchuan earthquake surface rupture and its seis-mogenic structure[J].Seismology and Geology,30(3):597—629(in Chinese).
张培震,邓起东,徐锡伟,等.1994.盲断裂、褶皱地震与新疆1906年玛纳斯地震[J].地震地质,16(3):193—204.ZHANG Pei-zhen,DENG Qi-dong,XU Xi-wei,et al.1994.Blind thrust,foldding earthquake,and the1906Manasearthquake,Xinjiang[J].Seismology and Geology,16(3):193—204(in Chinese).
中国地震信息网.2008.四川汶川县MS8.0地震参数[R].http://www.csi.ac.cn/sichuan/sichuan080512_csl.htm.China Seismic Information Net.2008.Seismological parameters for theMS8.0Wenchuan earthquake,Sichuan[R].http://www.csi.ac.cn/sichuan/sichuan080512_csl.htm(in Chinese).
Densmore AL,Eills MA,Li Y,et al.2007.Active tectonics of the Beichuan and Pengguan Faults at the eastern marginof the Tibetan Plateau[J].Tectonics,26.doi:10.1029/2006TC001987.
Jones L E,Helmberger D V.1998.Earthquake source parameters and fault kinematic in the eastern California shearzone[J].Bull Seism Soc Am,88(6):1337—1352.
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