鲜水河断裂带乾宁段古地震事件与大震复发行为
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摘要
鲜水河断裂带是巴颜喀拉和川滇2个强烈活动次级块体的边界带,为全球近代最活跃的断裂带之一,近300a就记录有9次7级以上大地震。2008年以来,巴颜喀拉块体东边界龙门山断裂带上相继发生了2008年汶川M_S8和2013年芦山M_S7大地震,南边界带西段玉树-甘孜断裂带上发生了2010年玉树M_S7.1地震,东段鲜水河断裂带上发生了2014年康定M_S6.3地震。研究其晚第四纪地表变形和大震复发行为是认识鲜水河断裂带乃至川西地区未来7级以上大地震危险性的重要基础工作。在前人工作基础上,文中通过地质地貌调查,在离逝时间相对较长的乾宁段上选择龙灯地点进行了组合探槽开挖,获得了鲜水河断裂带乾宁段距今约9 000a以来的5次(古)地震事件序列:8070—6395BC、5445—5125BC、4355—4180BC、625—1240AD和1893年乾宁地震,其大震复发行为并不遵循准周期复发模式,早期复发间隔1000~2000a,至4355—4180BC事件后,有过5 000a左右时长的平静期,之后又进入活跃期,1 000a BP左右以来发生了2次地表破裂型大地震。1893年乾宁地震在探槽地点一带的同震左旋位错量约2.9m。
The Xianshuihe Fault,the boundary of Bayan Har active tectonic block and Sichuan-Yunnan active tectonic block,is one of the most active fault zones in the world. In the past nearly 300 years,9 historical earthquakes of magnitude ≥ 7 have been recorded. Since 2008,several catastrophic earthquakes,such as Wenchuan M_S8 earthquake,Yushu M_S7. 1 earthquake and Lushan M_S7 earthquake,have occurred on the other Bayan Har block boundary fault zones. However,only the Kangding M_S6. 3 earthquake in 2014 was documented on the Xianshuihe Fault. Thus,the study of surface deformation and rupture behavior of large earthquakes in the late Quaternary on the Xianshuihe Fault is of fundamental importance for understanding the future seismic risk of this fault,and even the entire western Sichuan region. On the basis of the former work,combined with our detailed geomorphic and geological survey,we excavated a combined trench on the Qianning segment of Xianshuihe fault zone which has a long elapse time. Charcoal and woods in the trench are abundant.30 samples were dated to constrain the ages of the paleoseismic events. Five events were identified in the past 9 000 years,whose ages are: 8070—6395 BC,5445—5125 BC,4355—4180 BC,625—1240 AD and the Qianning earthquake in 1893. The large earthquake recurrence behavior on this segment does not follow the characteristic earthquake recurrence model. The recurrence interval is 1000 ~ 2000 years in early period and in turn there is a quiet period of about 5 000 years after 4355—4180 BC event. Then it enters the active period again. Two earthquakes with surface rupture occurred in the past 1000 years and the latest two earthquakes may have lower magnitude. The left-lateral coseismic displacement of the 1893 Qianning earthquake is about 2. 9m.
The Xianshuihe Fault,the boundary of Bayan Har active tectonic block and Sichuan-Yunnan active tectonic block,is one of the most active fault zones in the world. In the past nearly 300 years,9 historical earthquakes of magnitude ≥ 7 have been recorded. Since 2008,several catastrophic earthquakes,such as Wenchuan M_S8 earthquake,Yushu M_S7. 1 earthquake and Lushan M_S7 earthquake,have occurred on the other Bayan Har block boundary fault zones. However,only the Kangding M_S6. 3 earthquake in 2014 was documented on the Xianshuihe Fault. Thus,the study of surface deformation and rupture behavior of large earthquakes in the late Quaternary on the Xianshuihe Fault is of fundamental importance for understanding the future seismic risk of this fault,and even the entire western Sichuan region. On the basis of the former work,combined with our detailed geomorphic and geological survey,we excavated a combined trench on the Qianning segment of Xianshuihe fault zone which has a long elapse time. Charcoal and woods in the trench are abundant.30 samples were dated to constrain the ages of the paleoseismic events. Five events were identified in the past 9 000 years,whose ages are: 8070—6395 BC,5445—5125 BC,4355—4180 BC,625—1240 AD and the Qianning earthquake in 1893. The large earthquake recurrence behavior on this segment does not follow the characteristic earthquake recurrence model. The recurrence interval is 1000 ~ 2000 years in early period and in turn there is a quiet period of about 5 000 years after 4355—4180 BC event. Then it enters the active period again. Two earthquakes with surface rupture occurred in the past 1000 years and the latest two earthquakes may have lower magnitude. The left-lateral coseismic displacement of the 1893 Qianning earthquake is about 2. 9m.
引文
安艳芬.2010.鲜水河断裂带地震破裂段落的边界特征研究[D].北京:中国地震局地质研究所.AN Yan-fen.2010.Boundary features of the seismic rupture segments along the Xianshuihe fault zone[D].Institute of Geology,CEA,Beijing(in Chinese).
陈桂华.2006.川滇块体北东边界活动构造带的构造转换与变形分解作用[D].北京:中国地震局地质研究所.CHEN Gui-hua.2006.Structural transformation and strain partitioning along the northeast boundary belt of the Sichuan-Yunnan block[D].Institute of Geology,CEA,Beijing(in Chinese).
邓绍辉.2012.鲜水河断裂带上的历史地震[J].文史杂志,(2):68—72.DENG Shao-hui.2012.The historical earthquakes on the Xianshuihe fault zone[J].Journal of Literature and History,(2):68—72(in Chinese).
邓天岗,龙德雄.1986.鲜水河断裂带的基本结构与地震[J].地震研究,9(1):81—88.DENG Tian-gang,LONG De-xiong.1986.Basic structures of the Xianshui River Fault and the associated earthquakes[J].Journal of Seismological Research,9(1):81—88(in Chinese).
国家地震局地质研究所,宁夏回族自治区地震局.1990.海原活动断裂带[M].北京:地震出版社:229—234.Institute of Geology,China Earthquake Administration,Ningxia Earthquake Administration.1990.Haiyuan Active Fault Zone[M].Seismological Press,Beijing:229—234(in Chinese).
国家地震局震害防御司.1995.中国历史强震目录(公元前23世纪—公元1911年)[Z].北京:地震出版社:1 —514.Department of Earthquake Disaster Prevention,State Seismological Bureau.1995.Catalogue of Historical Strong Earthquakes in China(23rd Century B.C.to 1911)[Z].Seismological Press,Beijing:1—514(in Chinese).
李天祒.1997.鲜水河断裂带及强震危险性评估[M].成都:四川科学技术出版社.LI Tian-tiao.1997.The Xianshuihe Fault Zone and Assessment of Strong Earthquake Risk[M].Science and Technology Press of Sichuan,Chengdu(in Chinese).
龙德雄,邓天岗.1990.1786年康定地震形变特征的初步研究[J].地震研究,13(1):51—60.LONG De-xiong,DENG Tian-gang.1990.A preliminary study on the 1786 Kangding earthquake deformation characteristics[J].Journal of Seismological Research,13(1):51—60(in Chinese).
毛凤英,张培震.1995.古地震研究的逐次限定法与新疆北部主要断裂带的古地震研究[M]∥国家地震局地质研究所.活动断裂研究(4).北京:地震出版社:153—164.MAO Feng-ying,ZHANG Pei-zhen.1995.Progressive constraining method in paleoseismic study and paleoearthquakes along the major active faults in northern Xinjiang[M]∥Institute of Geology,State Seismological Bureau.Research of Active Fault(4).Seismological Press,Beijing:153—164(in Chinese).
钱洪,艾伦C R,罗灼礼,等.1988.全新世以来鲜水河断裂的活动特征[J].中国地震,4(2):9—18.QIAN Hong,Allen C R,LUO Zhuo-li,et al.1988.The active characteristics of Xianshuihe Fault in Holocene[J].Earthquake Research in China,4(2):9—18(in Chinese).
钱洪,罗灼礼,闻学泽.1990.鲜水河断裂带上特征地震的初步研究[J].地震学报,12(1):22—29.QIAN Hong,LUO Zhuo-li,WEN Xue-ze.1990.Preliminary study of characteristic earthquakes in the Xianshuihe fault zone[J].Acta Seismologica Sinica,12(1):22—29(in Chinese).
钱洪,唐荣昌,张成贵,等.1984.道孚地震地裂缝特征与震区的断层运动[J].地震研究,7(1):53—60.QIAN Hong,TANG Rong-chang,ZHANG Cheng-gui,et al.1984.Characteristics of ground fissures during the Daofu earthquake and movement of the faults in this earthquake area[J].Journal of Seismological Research,7(1):53 —60(in Chinese).
冉勇康,王虎,李彦宝,等.2012.中国大陆古地震研究的关键技术与案例解析(1):走滑活动断裂的探槽地点、布设与事件识别标志[J].地震地质,34(2):197—210.doi:10.3969/j.issn.0253-4967.2012.02.001.RAN Yong-kang,WANG Hu,LI Yan-bao,et al.2012.Key techniques and several cases analysis in paleoseismic studies in mainland China(1):Trenching sites,layouts and paleoseismic indicators on active strike-slip faults[J].Seismology and Geology,34(2):197—210(in Chinese).
冉勇康,王虎,杨会丽,等.2014.中国大陆古地震研究的关键技术与案例解析(4):古地震定年技术的样品采集和事件年代分析[J].地震地质,36(4):939—955.doi:10.3969/j.issn.0253-4967.2014.04.001.RAN Yong-kang,WANG Hu,YANG Hui-li,et al.2014.Key techniques and several cases analysis in paleoseismic studies in mainland China(4):Sampling and event analysis of paleoseismic dating methods[J].Seismology and Geology,36(4):939—955(in Chinese).
孙成民.2010a.四川地震全纪录(上卷)[M].成都:四川人民出版社:1—435.SUN Cheng-min.2010a.A Full Record of Sichuan Historical Earthquakes(A)[M].Sichuan People's Publishing House,Chengdu:1—435(in Chinese).
孙成民.2010b.四川地震全纪录(下卷)[M].成都:四川人民出版社:1—607.SUN Cheng-min.2010b.A Full Record of Sichuan Historical Earthquakes(B)[M].Sichuan People's Publishing House,Chengdu:1—607(in Chinese).
唐荣昌,钱洪,张文甫,等.1984.道孚6.9级地震的地质构造背景与发震构造条件分析[J].地震地质,6(2):33—40.TANG Rong-chang,QIAN Hong,ZHANG Wen-fu,et al.1984.On the seismogeological setting and conditions of seismogenic structures of 1981 Daofu earthquake[J].Seismology and Geology,6(2):33—40(in Chinese).
唐荣昌,文德华,邓天岗,等.1976.1973年炉霍7.9级地震的地裂缝特征及地震成因的初步探讨[J].地球物理学报,19(1):18—27,71—74.TANG Rong-chang,WEN De-hua,DENG Tian-gang,et al.1976.A preliminary study on the characteristics of the ground fractures during the Lu-Huo M=7.9 earthquake,1973 and the origin of the earthquake[J].Acta Geophysica Sinica,19(1):18—27,71—74(in Chinese).
闻学泽.2000.四川西部鲜水河-安宁河-则木河断裂带的地震破裂分段特征[J].地震地质,22(3):239—249.doi:10.3969/j.issn.0253-4967.2000.03.005.WEN Xue-ze.2000.Character of rupture segmentation of the Xianshuihe-Anninghe-Zemuhe fault zone,western Sichuan[J].Seismology and Geology,22(3):239—249(in Chinese).
闻学泽,易桂喜.2003.川滇地区地震活动统计单元的新划分[J].地震研究,26(S1):1—9.WEN Xue-ze,YI Gui-xi.2003.Re-zoning of statistic units of seismicity in Sichuan-Yunnan region[J].Journal of Seismological Research,26(S1):1—9(in Chinese).
徐锡伟,闻学泽,郑荣章,等.2003.川滇地区活动块体最新构造变动样式及其动力来源[J].中国科学(Ser D),33(S1):151—162.XU Xi-wei,WEN Xue-ze,ZHENG Rong-zhang,et al.2003.Pattern of latest tectonic motion and its dynamics for active blocks in Sichuan-Yunnan region,China[J].Science in China(Ser D),46(S2):210—226.
中国地震局震害防御司.1999.中国近代地震目录[Z].北京:中国科学技术出版社:1—637.Department of Earthquake Disaster Prevention,China Seismological Bureau.1999.The Catalogue of Modern Earthquakes in China[Z].China Science and Technology Press,Beijing:1—637(in Chinese).
周荣军,何玉林,黄祖智,等.2001.鲜水河断裂带乾宁—康定段的滑动速率与强震复发间隔[J].地震学报,23 (3):250—261.ZHOU Rong-jun,HE Yu-lin,HUANG Zu-zhi,et al.2001.The slip rate and strong earthquake recurrence interval on the Qianning-Kangding segment of the Xianshuihe fault zone[J].Acta Seismologica Sinica,23(3):250—261(in Chinese).
Allen C R,Luo Z L,Qian H,et al.1991.Field study of a highly active fault zone:The Xianshuihe Fault of southwestern China[J].The Geological Society of America Bulletin,103(9):1178—1199.
Deng Q D,Wu D N,Zhang P Z,et al.1986.Structure and deformational character of strike-slip fault zones[J].Pure and Applied Geophysics,124(1-2):203—223.
Ran Y K,Zhang P Z,Chen L C.2003.Late Quaternary history of paleoseismic activity along the Hohhot segment of the Daqingshan piedmont fault in Hetao depression zone,North China[J].Annals of Geophysics,46(5):1053—1069.
Wen X Z,Ma S L,Xu X W,et al.2008.Historical pattern and behavior of earthquake ruptures along the eastern boundary of the Sichuan-Yunnan faulted-block,southwestern China[J].Physics of the Earth and Planetary Interiors,168(1-2):16—36.
Zhao G G,Liu D Q,Wei W,et al.1990.The late Quaternary slip rate and segmentation of the Xianshuihe active fault zone[C]∥Proceedings of the PRC-USA Bilateral Symposium on the Xianshuihe Fault Zone.Seismological Press,Beijing:41—57.
陈桂华.2006.川滇块体北东边界活动构造带的构造转换与变形分解作用[D].北京:中国地震局地质研究所.CHEN Gui-hua.2006.Structural transformation and strain partitioning along the northeast boundary belt of the Sichuan-Yunnan block[D].Institute of Geology,CEA,Beijing(in Chinese).
邓绍辉.2012.鲜水河断裂带上的历史地震[J].文史杂志,(2):68—72.DENG Shao-hui.2012.The historical earthquakes on the Xianshuihe fault zone[J].Journal of Literature and History,(2):68—72(in Chinese).
邓天岗,龙德雄.1986.鲜水河断裂带的基本结构与地震[J].地震研究,9(1):81—88.DENG Tian-gang,LONG De-xiong.1986.Basic structures of the Xianshui River Fault and the associated earthquakes[J].Journal of Seismological Research,9(1):81—88(in Chinese).
国家地震局地质研究所,宁夏回族自治区地震局.1990.海原活动断裂带[M].北京:地震出版社:229—234.Institute of Geology,China Earthquake Administration,Ningxia Earthquake Administration.1990.Haiyuan Active Fault Zone[M].Seismological Press,Beijing:229—234(in Chinese).
国家地震局震害防御司.1995.中国历史强震目录(公元前23世纪—公元1911年)[Z].北京:地震出版社:1 —514.Department of Earthquake Disaster Prevention,State Seismological Bureau.1995.Catalogue of Historical Strong Earthquakes in China(23rd Century B.C.to 1911)[Z].Seismological Press,Beijing:1—514(in Chinese).
李天祒.1997.鲜水河断裂带及强震危险性评估[M].成都:四川科学技术出版社.LI Tian-tiao.1997.The Xianshuihe Fault Zone and Assessment of Strong Earthquake Risk[M].Science and Technology Press of Sichuan,Chengdu(in Chinese).
龙德雄,邓天岗.1990.1786年康定地震形变特征的初步研究[J].地震研究,13(1):51—60.LONG De-xiong,DENG Tian-gang.1990.A preliminary study on the 1786 Kangding earthquake deformation characteristics[J].Journal of Seismological Research,13(1):51—60(in Chinese).
毛凤英,张培震.1995.古地震研究的逐次限定法与新疆北部主要断裂带的古地震研究[M]∥国家地震局地质研究所.活动断裂研究(4).北京:地震出版社:153—164.MAO Feng-ying,ZHANG Pei-zhen.1995.Progressive constraining method in paleoseismic study and paleoearthquakes along the major active faults in northern Xinjiang[M]∥Institute of Geology,State Seismological Bureau.Research of Active Fault(4).Seismological Press,Beijing:153—164(in Chinese).
钱洪,艾伦C R,罗灼礼,等.1988.全新世以来鲜水河断裂的活动特征[J].中国地震,4(2):9—18.QIAN Hong,Allen C R,LUO Zhuo-li,et al.1988.The active characteristics of Xianshuihe Fault in Holocene[J].Earthquake Research in China,4(2):9—18(in Chinese).
钱洪,罗灼礼,闻学泽.1990.鲜水河断裂带上特征地震的初步研究[J].地震学报,12(1):22—29.QIAN Hong,LUO Zhuo-li,WEN Xue-ze.1990.Preliminary study of characteristic earthquakes in the Xianshuihe fault zone[J].Acta Seismologica Sinica,12(1):22—29(in Chinese).
钱洪,唐荣昌,张成贵,等.1984.道孚地震地裂缝特征与震区的断层运动[J].地震研究,7(1):53—60.QIAN Hong,TANG Rong-chang,ZHANG Cheng-gui,et al.1984.Characteristics of ground fissures during the Daofu earthquake and movement of the faults in this earthquake area[J].Journal of Seismological Research,7(1):53 —60(in Chinese).
冉勇康,王虎,李彦宝,等.2012.中国大陆古地震研究的关键技术与案例解析(1):走滑活动断裂的探槽地点、布设与事件识别标志[J].地震地质,34(2):197—210.doi:10.3969/j.issn.0253-4967.2012.02.001.RAN Yong-kang,WANG Hu,LI Yan-bao,et al.2012.Key techniques and several cases analysis in paleoseismic studies in mainland China(1):Trenching sites,layouts and paleoseismic indicators on active strike-slip faults[J].Seismology and Geology,34(2):197—210(in Chinese).
冉勇康,王虎,杨会丽,等.2014.中国大陆古地震研究的关键技术与案例解析(4):古地震定年技术的样品采集和事件年代分析[J].地震地质,36(4):939—955.doi:10.3969/j.issn.0253-4967.2014.04.001.RAN Yong-kang,WANG Hu,YANG Hui-li,et al.2014.Key techniques and several cases analysis in paleoseismic studies in mainland China(4):Sampling and event analysis of paleoseismic dating methods[J].Seismology and Geology,36(4):939—955(in Chinese).
孙成民.2010a.四川地震全纪录(上卷)[M].成都:四川人民出版社:1—435.SUN Cheng-min.2010a.A Full Record of Sichuan Historical Earthquakes(A)[M].Sichuan People's Publishing House,Chengdu:1—435(in Chinese).
孙成民.2010b.四川地震全纪录(下卷)[M].成都:四川人民出版社:1—607.SUN Cheng-min.2010b.A Full Record of Sichuan Historical Earthquakes(B)[M].Sichuan People's Publishing House,Chengdu:1—607(in Chinese).
唐荣昌,钱洪,张文甫,等.1984.道孚6.9级地震的地质构造背景与发震构造条件分析[J].地震地质,6(2):33—40.TANG Rong-chang,QIAN Hong,ZHANG Wen-fu,et al.1984.On the seismogeological setting and conditions of seismogenic structures of 1981 Daofu earthquake[J].Seismology and Geology,6(2):33—40(in Chinese).
唐荣昌,文德华,邓天岗,等.1976.1973年炉霍7.9级地震的地裂缝特征及地震成因的初步探讨[J].地球物理学报,19(1):18—27,71—74.TANG Rong-chang,WEN De-hua,DENG Tian-gang,et al.1976.A preliminary study on the characteristics of the ground fractures during the Lu-Huo M=7.9 earthquake,1973 and the origin of the earthquake[J].Acta Geophysica Sinica,19(1):18—27,71—74(in Chinese).
闻学泽.2000.四川西部鲜水河-安宁河-则木河断裂带的地震破裂分段特征[J].地震地质,22(3):239—249.doi:10.3969/j.issn.0253-4967.2000.03.005.WEN Xue-ze.2000.Character of rupture segmentation of the Xianshuihe-Anninghe-Zemuhe fault zone,western Sichuan[J].Seismology and Geology,22(3):239—249(in Chinese).
闻学泽,易桂喜.2003.川滇地区地震活动统计单元的新划分[J].地震研究,26(S1):1—9.WEN Xue-ze,YI Gui-xi.2003.Re-zoning of statistic units of seismicity in Sichuan-Yunnan region[J].Journal of Seismological Research,26(S1):1—9(in Chinese).
徐锡伟,闻学泽,郑荣章,等.2003.川滇地区活动块体最新构造变动样式及其动力来源[J].中国科学(Ser D),33(S1):151—162.XU Xi-wei,WEN Xue-ze,ZHENG Rong-zhang,et al.2003.Pattern of latest tectonic motion and its dynamics for active blocks in Sichuan-Yunnan region,China[J].Science in China(Ser D),46(S2):210—226.
中国地震局震害防御司.1999.中国近代地震目录[Z].北京:中国科学技术出版社:1—637.Department of Earthquake Disaster Prevention,China Seismological Bureau.1999.The Catalogue of Modern Earthquakes in China[Z].China Science and Technology Press,Beijing:1—637(in Chinese).
周荣军,何玉林,黄祖智,等.2001.鲜水河断裂带乾宁—康定段的滑动速率与强震复发间隔[J].地震学报,23 (3):250—261.ZHOU Rong-jun,HE Yu-lin,HUANG Zu-zhi,et al.2001.The slip rate and strong earthquake recurrence interval on the Qianning-Kangding segment of the Xianshuihe fault zone[J].Acta Seismologica Sinica,23(3):250—261(in Chinese).
Allen C R,Luo Z L,Qian H,et al.1991.Field study of a highly active fault zone:The Xianshuihe Fault of southwestern China[J].The Geological Society of America Bulletin,103(9):1178—1199.
Deng Q D,Wu D N,Zhang P Z,et al.1986.Structure and deformational character of strike-slip fault zones[J].Pure and Applied Geophysics,124(1-2):203—223.
Ran Y K,Zhang P Z,Chen L C.2003.Late Quaternary history of paleoseismic activity along the Hohhot segment of the Daqingshan piedmont fault in Hetao depression zone,North China[J].Annals of Geophysics,46(5):1053—1069.
Wen X Z,Ma S L,Xu X W,et al.2008.Historical pattern and behavior of earthquake ruptures along the eastern boundary of the Sichuan-Yunnan faulted-block,southwestern China[J].Physics of the Earth and Planetary Interiors,168(1-2):16—36.
Zhao G G,Liu D Q,Wei W,et al.1990.The late Quaternary slip rate and segmentation of the Xianshuihe active fault zone[C]∥Proceedings of the PRC-USA Bilateral Symposium on the Xianshuihe Fault Zone.Seismological Press,Beijing:41—57.