汶川8.0级地震发震断层的累积地震位错研究
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摘要
2008年5月12日,四川省汶川县内发生MS8.0地震。此次地震沿龙门山中央断裂产生1条长达200km的同震地表破裂带。文中选择位于地震地表破裂带北段的南坝镇、凤凰村以及南段的映秀镇这3个地点,以被断层错断的河流阶地为研究对象,对多级阶地面上的地震地表破裂及断层陡坎地貌进行了野外实测工作。经过测量数据的计算和分析,得到了各级阶地上断层陡坎的高度,该值即为该阶地记录的地震断层的累积垂直位错量。若以本次地震的垂直位错量作为古地震位错量的均值,则可计算得到每级阶地累积的地震次数。研究结果表明,各点T1阶地形成以来仅经历过1次事件,即本次地震事件;T2阶地形成以来约经历了5次事件;T3阶地形成以来约经历了9～11次事件;T4阶地形成以来约经历了20次事件。在本文研究的基础上,结合前人的阶地测年数据,则可获得古地震复发间隔的可靠数据。
The May 12,2008 MS 8.0 Wenchuan earthquake in Sichuan Province,China produced a 240km long co-seismic surface rupture zone along the Longmenshan Central Fault.Our investigation focuses mainly on the three regions along the co-seismic surface ruptures,i.e.the Nanba Town and the Fenghuang village on the northern segment of the rupture zone,and the Yingxiu town on the southern segment.We studied the river terraces in these regions offset by the active fault,measured the surface ruptures and the fault scarps on the multilevel terraces and obtained the height of the fault scarps on each terrace,namely,the cumulative vertical slip of the active fault recorded by terrace,through data calculation and analysis.If we use the vertical slip of this earthquake as the average vertical slip of the paleoearthquakes,then the ratio of the cumulative vertical slip of each terrace to this average vertical slip is the cumulative times of paleoearthquakes recorded by each terrace.The research results show that T1 of every study area has undergone only one paleoearthquake event ever since its formation,T2 about 5 paleoearthquake events,T3 about 9～11 paleoearthquakes and T4 about 20 paleoearthquakes.Based on the research result of this paper,and combined with the previously dating ages of the terraces,we can obtain some reliable data about the recurrence intervals of the paleoearthquakes.
The May 12,2008 MS 8.0 Wenchuan earthquake in Sichuan Province,China produced a 240km long co-seismic surface rupture zone along the Longmenshan Central Fault.Our investigation focuses mainly on the three regions along the co-seismic surface ruptures,i.e.the Nanba Town and the Fenghuang village on the northern segment of the rupture zone,and the Yingxiu town on the southern segment.We studied the river terraces in these regions offset by the active fault,measured the surface ruptures and the fault scarps on the multilevel terraces and obtained the height of the fault scarps on each terrace,namely,the cumulative vertical slip of the active fault recorded by terrace,through data calculation and analysis.If we use the vertical slip of this earthquake as the average vertical slip of the paleoearthquakes,then the ratio of the cumulative vertical slip of each terrace to this average vertical slip is the cumulative times of paleoearthquakes recorded by each terrace.The research results show that T1 of every study area has undergone only one paleoearthquake event ever since its formation,T2 about 5 paleoearthquake events,T3 about 9～11 paleoearthquakes and T4 about 20 paleoearthquakes.Based on the research result of this paper,and combined with the previously dating ages of the terraces,we can obtain some reliable data about the recurrence intervals of the paleoearthquakes.
引文
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 geodynamics of the LongmenshanMountains and its adjacent regions[J].Seismology and Geology,16(4):389—403(in Chinese).
何宏林,孙昭民,王世元,等.2008.汶川MS8.0级地震地表破裂带[J].地震地质,30(2):359—362.HE Hong-lin,SUN Zhao-min,WANG Shi-yuan,et al.2008.Rupture of theMS8.0Wenchuan earthquake[J].Seismol-ogy and Geology,30(2):359—362(in Chinese).
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马保起,苏刚,侯志华,等.2005.利用岷江阶地的变形估算龙门山断裂带中段晚第四纪滑动速率[J].地震地质,27(2):234—242.MA Bao-qi,SU Gang,HOU Zhi-hua,et al.2005.Late Quaternary slip rate in the central part of the Longmenshan Faultzone from terrace deformation along the Minjiang River[J].Seismology and Geology,27(2):234—242(in Chi-nese).
马保起,张世民,田勤俭,等.2008.汶川8.0级地震地表破裂带[J].第四纪研究,28(4):513—517.MA Bao-qi,ZHANG Shi-min,TIAN Qin-jian,et al.2008.Surface rupture of theMS8.0Wenchuan earthquake[J].Quaternary Sciences,28(4):513—517(in Chinese).
冉勇康,陈立春,陈桂华,等.2008.汶川MS8.0地震发震断裂大地震原地重复现象初析[J].地震地质,30(3):630—643.RAN Yong-kang,CHEN Li-chun,CHEN Gui-hua,et al.2008.Primary analysis of in-situ recurrence of large earthquakealong seismogenic fault of theMS8.0Wenchuan earthquake[J].Seismology and Geology,30(3):630—643(inChinese).
唐荣昌,文德华,黄祖智,等.1991.松潘—龙门山地区主要活动断裂带第四纪活动特征[J].中国地震,7(3):64—71.TANG Rong-chang,WEN De-hua,HUANF Zu-zhi,et al.1991.The Quaternary activity characteristics of several majoractive faults in the Songpan-Longmenshan region[J].Earthquake Research in China,7(3):64—71(in Chi-nese).
王二七,孟庆任,陈智梁,等.2001.龙门山断裂带印支期左旋走滑运动及其大地构造成因[J].地学前缘,8(2):375—384.WANG Er-qi,MENG Qing-ren,CHEN Zhi-liang,et al.2001.Early Mesozoic left-lateral movement along the LongmenShan Fault belt and its tectonic implications[J].Earth Science Frontiers,8(2):375—384(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 ruptures and its seis-mogenic structure[J].Seismology and Geology,30(3):597—629(in Chinese).
许志琴,侯立玮,王宗秀,等.1992.中国松潘-甘孜造山带的造山过程[M].北京:地质出版社.XU Zhi-qin,HOU Li-wei,WANG Zong-xiu,et al.1992.Mountain Building Process of the Songpan-Ganzi Orogeny,Chi-na[M].Geological Publishing House,Beijing(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008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[J].地球物理学报,51(4):1066—1073.ZHANG Pei-zhen,XU Xi-wei,WEN Xue-ze,et al.2008.Slip rates and recurrence intervals of the Longmenshan activefault zone,and tectonic implications for the mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese Journal of Geophysics,51(4):1066—1073(in Chinese).
赵小麟,邓起东,陈社发.1994.龙门山逆断裂带中段的构造地貌学研究[J].地震地质,16(4):422—428.ZHAO Xiao-lin,DENG Qi-dong,CHEN She-fa.1994.Tectonic geomorphology of the central segment of the Longmen-shan thrust belt,western Sichuan,southwestern China[J].Seismology and Geology,16(4):422—428(in Chi-nese).
周荣军,李勇,Alexander L D,等.2006.青藏高原东缘活动构造[J].矿物岩石,26(2):40—51.ZHOU Rong-jun,LI Yong,Alexander L D,et al.2006.Active tectonics of the eastern margin of the Tibet Plateau[J].Journal of Mineralogy and Petrology,26(2):40—51(in Chinese).
何宏林,孙昭民,王世元,等.2008.汶川MS8.0级地震地表破裂带[J].地震地质,30(2):359—362.HE Hong-lin,SUN Zhao-min,WANG Shi-yuan,et al.2008.Rupture of theMS8.0Wenchuan earthquake[J].Seismol-ogy and Geology,30(2):359—362(in Chinese).
李勇,周荣军,Alexander L D,等.2006.青藏高原东缘大陆动力学过程与地质响应[M].北京:地质出版社.LI Yong,ZHOU Rong-jun,Alexander L D,et al.2006.Continental Dynamics and Geological Response of the EasternMargin of Qinghai-Tibet Plateau[M].Geological Publishing House,Beijing(in Chinese).
马保起,苏刚,侯志华,等.2005.利用岷江阶地的变形估算龙门山断裂带中段晚第四纪滑动速率[J].地震地质,27(2):234—242.MA Bao-qi,SU Gang,HOU Zhi-hua,et al.2005.Late Quaternary slip rate in the central part of the Longmenshan Faultzone from terrace deformation along the Minjiang River[J].Seismology and Geology,27(2):234—242(in Chi-nese).
马保起,张世民,田勤俭,等.2008.汶川8.0级地震地表破裂带[J].第四纪研究,28(4):513—517.MA Bao-qi,ZHANG Shi-min,TIAN Qin-jian,et al.2008.Surface rupture of theMS8.0Wenchuan earthquake[J].Quaternary Sciences,28(4):513—517(in Chinese).
冉勇康,陈立春,陈桂华,等.2008.汶川MS8.0地震发震断裂大地震原地重复现象初析[J].地震地质,30(3):630—643.RAN Yong-kang,CHEN Li-chun,CHEN Gui-hua,et al.2008.Primary analysis of in-situ recurrence of large earthquakealong seismogenic fault of theMS8.0Wenchuan earthquake[J].Seismology and Geology,30(3):630—643(inChinese).
唐荣昌,文德华,黄祖智,等.1991.松潘—龙门山地区主要活动断裂带第四纪活动特征[J].中国地震,7(3):64—71.TANG Rong-chang,WEN De-hua,HUANF Zu-zhi,et al.1991.The Quaternary activity characteristics of several majoractive faults in the Songpan-Longmenshan region[J].Earthquake Research in China,7(3):64—71(in Chi-nese).
王二七,孟庆任,陈智梁,等.2001.龙门山断裂带印支期左旋走滑运动及其大地构造成因[J].地学前缘,8(2):375—384.WANG Er-qi,MENG Qing-ren,CHEN Zhi-liang,et al.2001.Early Mesozoic left-lateral movement along the LongmenShan Fault belt and its tectonic implications[J].Earth Science Frontiers,8(2):375—384(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 ruptures and its seis-mogenic structure[J].Seismology and Geology,30(3):597—629(in Chinese).
许志琴,侯立玮,王宗秀,等.1992.中国松潘-甘孜造山带的造山过程[M].北京:地质出版社.XU Zhi-qin,HOU Li-wei,WANG Zong-xiu,et al.1992.Mountain Building Process of the Songpan-Ganzi Orogeny,Chi-na[M].Geological Publishing House,Beijing(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008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[J].地球物理学报,51(4):1066—1073.ZHANG Pei-zhen,XU Xi-wei,WEN Xue-ze,et al.2008.Slip rates and recurrence intervals of the Longmenshan activefault zone,and tectonic implications for the mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese Journal of Geophysics,51(4):1066—1073(in Chinese).
赵小麟,邓起东,陈社发.1994.龙门山逆断裂带中段的构造地貌学研究[J].地震地质,16(4):422—428.ZHAO Xiao-lin,DENG Qi-dong,CHEN She-fa.1994.Tectonic geomorphology of the central segment of the Longmen-shan thrust belt,western Sichuan,southwestern China[J].Seismology and Geology,16(4):422—428(in Chi-nese).
周荣军,李勇,Alexander L D,等.2006.青藏高原东缘活动构造[J].矿物岩石,26(2):40—51.ZHOU Rong-jun,LI Yong,Alexander L D,et al.2006.Active tectonics of the eastern margin of the Tibet Plateau[J].Journal of Mineralogy and Petrology,26(2):40—51(in Chinese).
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