2010年玉树地震地表破裂带典型破裂样式及其构造意义
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摘要
野外调查表明,青海玉树MS7.1地震发生在青藏高原中部甘孜—玉树断裂的玉树段上,在玉树县结古镇至隆宝镇之间产生了一系列包括剪切破裂、张剪切破裂、压剪切破裂、张性破裂及其不连续岩桥区出现的鼓包或陷落坑(拉分盆地)、高寒地区特有的冰裂缝等地表破裂单元,它们斜列组合成整体走向约300°、长约65km、最大同震左旋位移2.4m的地表破裂带,具有变形局部化的基本特征.玉树地震地表破裂带整体上可划分为长约15km的结隆次级地表破裂带和长约31km的结古次级地表破裂带,两者呈左阶羽列,其间无地表破裂段长约17km,对应于MW6.4和MW6.9两个次级地震事件.地表破裂类型、基本组合特征等显示出甘孜—玉树断裂两盘块体的运动方式以纯剪切的左旋走滑为主,从一个方面反映了青藏高原物质存在着向东的逃逸和挤出现象.
Field investigations show that the Yushu,Qinghai Province,MS7.1 earthquake occurred on the Yushu segment of the Ganzê-Yushu fault in the Qinghai-Tibetan Plateau.Its surface rupture zone is distributed along the Yushu segment between Longbao Town and Jiegu Town and consists of shear cracks,transtensional cracks,transpressional cracks,tension cracks,mole tracks in right-stepovers or small pull-aparts in left-stepovers between en echelon cracks with left-lateral component.Those ruptures are en echelon to form an ～300°-striking earthquake surface rupture zone with a total length of about 65 km.The maximum co-seismic left-lateral displacement is 2.4 m.The width of the surface rupture zone is in general less than 30 m,showing a localized rupturing feature.The Yushu earthquake surface rupture zone can be divided into two relatively independent sections in left-step: the Jielong section ～15 km long with a maximum left-lateral slip of 0.66 m and Jiegu section ～ 31 km with a maximum left-lateral slip of 2.4 m,and between them is a 17 km-long-section where no surface ruptures occurred,which correspond to two subevents with MW6.4 and MW6.9,respectively.This kind of the surface rupture pattern shows that the Ganzê-Yushu fault,a seismogenic fault of the Yushu earthquake,is dominated by a pure left-lateral faulting and the eastward escape of the Qinghai-Tibetan Plateau exists.
Field investigations show that the Yushu,Qinghai Province,MS7.1 earthquake occurred on the Yushu segment of the Ganzê-Yushu fault in the Qinghai-Tibetan Plateau.Its surface rupture zone is distributed along the Yushu segment between Longbao Town and Jiegu Town and consists of shear cracks,transtensional cracks,transpressional cracks,tension cracks,mole tracks in right-stepovers or small pull-aparts in left-stepovers between en echelon cracks with left-lateral component.Those ruptures are en echelon to form an ～300°-striking earthquake surface rupture zone with a total length of about 65 km.The maximum co-seismic left-lateral displacement is 2.4 m.The width of the surface rupture zone is in general less than 30 m,showing a localized rupturing feature.The Yushu earthquake surface rupture zone can be divided into two relatively independent sections in left-step: the Jielong section ～15 km long with a maximum left-lateral slip of 0.66 m and Jiegu section ～ 31 km with a maximum left-lateral slip of 2.4 m,and between them is a 17 km-long-section where no surface ruptures occurred,which correspond to two subevents with MW6.4 and MW6.9,respectively.This kind of the surface rupture pattern shows that the Ganzê-Yushu fault,a seismogenic fault of the Yushu earthquake,is dominated by a pure left-lateral faulting and the eastward escape of the Qinghai-Tibetan Plateau exists.
引文
[1]http://www.cea.gov.cn/manage/html/8a8587881632fa5c0116674a018300cf/qhys7.1/index.html[2010-09-24].
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[12]Tapponnier P,Xu Z Q,Roger F,et al.Oblique stepwise riseand growth of the Tibet plateau.Science,2001,294(5547):1671-1677.
[13]Xu X W,Yeats R S,Yu G H.Five short historicalearthquake surface ruptures near the Silk Road,GansuProvince,China.Bulletin of the Seismological Society ofAmerica,2010,100(2):541-561,doi:10.1785/0120080282.
[14]Yeats R S,Sieh K,Allen C R.The Geology of Earthquakes.Oxford:Oxford Univ.Press,1997:568.
[15]徐锡伟,于贵华,马文涛等.昆仑山地震(Mw7.8)破裂行为、变形局部化特征及其构造内涵讨论.中国科学D辑:地球科学,2008,38(7):785-796.Xu X W,Yu G H,Ma W T,et al.Rupture behavior anddeformation localization of the Kunlunshan earthquake(Mw7.8)and their tectonic implications.Science in ChinaSeries D:Earth Sciences,2008,51(10):1361-1374.
[16]Xu X W,Wen X Z,Yu G H,et al.Co-seismic reverse-andoblique-slip surface faulting generated by the 2008 Mw7.9Wenchuan earthquake,China.Geology,2009,37(6):515-518,doi:10.1130/G25462A.1.
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[18]Xu X W,Chen W B,Ma W T,et al.Surface rupture of theKunlun earthquake(Ms8.1),northern Tibetan Plateau,China.Seismological Research Letters,2002,73(6):884-892.
[19]Deng Q D,Wu D N,Zhang P Z,et al.Structure anddeformational character of strike-slip fault zones.Pure andApplied Geophysics,1986,124(1-2):203-223.
[20]Plafker G.Tectonic aspects of the Guatemala earthquake of 4February 1976.Science,1976,193(4259):1201-1208.
[21]Tchalenko J S.Similarities between shear zones of differentmagnitudes.Geol.Soc.America Bull.,1970,81(6):1625-1640.
[22]Yu G,Xu X,Klinger Y,et al.Fault-scarp features andcascading-rupture model for the Mw7.9 Wenchuan earthquake,eastern Tibetan plateau,China.Bull.Seismol.Soc.Am.,2010,100(5B):2590-2614.
[23]邵芸,谢酬,岳中琦等.青海玉树地震差分干涉雷达同震形变测量.遥感学报,2010,14(5):1029-1037.Shao Y,Xie C,Yue Z Q,et al.Co-seismic grounddeformation of Yushu Earthquake detected with D-InSARtechnique.Journal of Remote Sensing(in Chinese),2010,14(5):1029-1037.
[24]Knuepfer P L K.Implications of the characteristics of end-points of historical surface fault ruptures for the nature offault segmentation.U.S.G.S.Open-File Report,1989:89-135,193-228.
[25]Cunningham W D,Mann P.Tectonics of strike-sliprestraining and releasing bends.Geological Society,2007,290(1):1-12,doi:10.1144/SP290.1.
[26]Wells D L,Coppersmith K J.New empirical relationshipsamong magnitude,rupture length,rupture width,rupturearea,and surface displacement.Bull.Seismol.Soc.Am.,1994,84(4):974-1002.
[27]刁桂苓,王晓山,高国英等.以震源机制类型划分汶川、玉树地震构造块体归属.地球物理学报,2010,53(8):1778-1783.Diao G L,Wang X S,Gao G Y,et al.Tectonic blockattribution of Wenchuan and Yushu earthquakes distinguishedby focal mechanism type.Chinese J.Geophys.(in Chinese),2010,53(8):1778-1783.
[28]Xu X W,Wang F,Zheng R Z,et al.Late Quaternarysinistral slip rate along the Altyn Tagh fault and its structuraltransformation model.Science in China Series D:EarthSciences,2005,48(3):384-397.
[29]Fu B H,Awata Y.Displacement and timing of left-lateralfaulting in the Kunlun Fault Zone,northern Tibet,inferredfrom geologic and geomorphic features.Journal of AsianEarth Sciences,2007,29(2-3):253-265.
[30]Zhang Z J,Klemperer S L,Bai Z M,et al.Crustal structureof the Paleozoic Kunlun orogeny from an active-source seismicprofile between Moba and Guide in East Tibet,China.Gondwana Research,2011,19(4):944-1007,doi:10.1016/j.gr.2010.09.008.
[31]Zhang Z J,Wang Y H,Chen Y,et al.Crustal structureacross Longmenshan fault belt from passive source seismicprofiling.Geophysical Research Letter,2009,36:L17310.
[32]Fu B H,Shi P L,Guo H D,et al.Surface deformationrelated to the 2008 Wenchuan earthquake,and mountainbuilding of the Longmen Shan,eastern Tibetan Plateau.Journal of Asian Earth Sciences,2011,40(4):805-824,doi:10.1016/j.jseaes.2010.11.011.
[33]Zhang Z J,Yuan X H,Chen Y,et al.Seismic signature ofthe collision between the east Tibetan escape flow and theSichuan Basin.Earth and Planetary Science Letter,2010,292(3-4):254-264.
[2]刘超,许力生,陈运泰.2010年4月14日青海玉树地震快速矩张量解.地震学报,2010,32(3):366-368.Liu C,Xu L S,Chen Y T.Quick moment tensor solution for14April 2010Yushu,Qinghai,earthquake.Acta SeismologicaSinica(in Chinese),2010,32(3):366-368.
[3]张勇,许力生,陈运泰.2010年4月14日青海玉树地震破裂过程快速反演.地震学报,2010,32(3):361-365.Zhang Y,Xu L S,Chen Y T.Fast inversion of ruptureprocess for 14April 2010Yushu,Qinghai,earthquake.ActaSeismologica Sinica(in Chinese),2010,32(3):361-365.
[4]倪四道,王伟涛,李丽.2010年4月14日玉树地震:一个有前震的破坏性地震.中国科学(D辑):地球科学,2010,40(5):535-537.Ni S D,Wang W T,Li L.The April 14th,2010 Yushuearthquake,a devastating earthquake with foreshocks.Sci.China Earth Sci.,2010,53(6):791-793.
[5]陈立春,王虎,冉勇康等.玉树MS7.1级地震地表破裂与历史大地震.科学通报,2010,55(13):1200-1205.Chen L C,Wang H,Ran Y K,et al.The Ms7.1 Yushuearthquake surface ruptures and historical earthquakes.Chinese Sci.Bull.(in Chinese),2010,50(13):1200-1205.
[6]张桂芳,屈春燕,单新建等.2010年青海玉树MS7.1级地震地表破裂带和形变特征分析.地球物理学报,2011,54(1):121-127.Zhang G F,Qu C Y,Shan X J,et al.The surface ruptureand coseismic deformation characteristics of the Ms7.1earthquake at Qinghai Yushu in 2010.Chinese J.Geophys.(in Chinese),2011,54(1):121-127.
[7]周荣军,马声浩,蔡长星.甘孜—玉树断裂带的晚第四纪活动特征.中国地震,1996,12(3):250-260.Zhou R J,Ma S H,Cai C X,et al.Late Quaternary activefeatures of the Ganzi-Yushu fault zone.Earthquake Researchin China(in Chinese),1996,12(3):250-260.
[8]闻学泽,徐锡伟,郑荣章等.甘孜—玉树断裂的平均滑动速率与近代大地震破裂.中国科学(D辑),2003,33(增):199-208.Wen X Z,Xu X W,Zheng R Z,et al.The average slip rateand the surface rupture of recent earthquakes Ganzi-Yushufault zone.Science in China(Series D)(in Chinese),2003,33(Suppl.1):200-208.
[9]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):151-162.Xu X W,Wen X Z,Zheng R Z,et al.Pattern of latesttectonic motion and its dynamics for active blocks in Sichuan-Yunnan region,China.Science in China(Series D),2003,46(Suppl.2):210-226.
[10]国家地震局震害防御司.中国近代地震目录.北京:科学与技术出版社,1999:637.Division of Earthquake Monitoring and Prediction CEA.TheCatalogue of Modern Earthquakes in China(in Chinese).Beijing:China Science and Technology Press,1999:637.
[11]周荣军,闻学泽,蔡长星等.甘孜—玉树断裂带的近代地震与未来地震趋势估计.地震地质,1997,19(2):115-124.Zhou R J,Wen X Z,Cai C X,et al.Recent earthquakes andassessment of seismic tendency on the Ganzi Yushu faultzone.Seismology and Geology(in Chinese),1997,19(2):115-124.
[12]Tapponnier P,Xu Z Q,Roger F,et al.Oblique stepwise riseand growth of the Tibet plateau.Science,2001,294(5547):1671-1677.
[13]Xu X W,Yeats R S,Yu G H.Five short historicalearthquake surface ruptures near the Silk Road,GansuProvince,China.Bulletin of the Seismological Society ofAmerica,2010,100(2):541-561,doi:10.1785/0120080282.
[14]Yeats R S,Sieh K,Allen C R.The Geology of Earthquakes.Oxford:Oxford Univ.Press,1997:568.
[15]徐锡伟,于贵华,马文涛等.昆仑山地震(Mw7.8)破裂行为、变形局部化特征及其构造内涵讨论.中国科学D辑:地球科学,2008,38(7):785-796.Xu X W,Yu G H,Ma W T,et al.Rupture behavior anddeformation localization of the Kunlunshan earthquake(Mw7.8)and their tectonic implications.Science in ChinaSeries D:Earth Sciences,2008,51(10):1361-1374.
[16]Xu X W,Wen X Z,Yu G H,et al.Co-seismic reverse-andoblique-slip surface faulting generated by the 2008 Mw7.9Wenchuan earthquake,China.Geology,2009,37(6):515-518,doi:10.1130/G25462A.1.
[17]Xu X W,Yu G H,Klinger Y,et al.Reevaluation of surfacerupture parameters and faulting segmentation of the 2001Kunlunshan earthquake(Mw7.8),Northern Tibetan Plateau,China.Journal Geophysics Research,2006,111,B05316,doi:10.1029/2004JB003488.
[18]Xu X W,Chen W B,Ma W T,et al.Surface rupture of theKunlun earthquake(Ms8.1),northern Tibetan Plateau,China.Seismological Research Letters,2002,73(6):884-892.
[19]Deng Q D,Wu D N,Zhang P Z,et al.Structure anddeformational character of strike-slip fault zones.Pure andApplied Geophysics,1986,124(1-2):203-223.
[20]Plafker G.Tectonic aspects of the Guatemala earthquake of 4February 1976.Science,1976,193(4259):1201-1208.
[21]Tchalenko J S.Similarities between shear zones of differentmagnitudes.Geol.Soc.America Bull.,1970,81(6):1625-1640.
[22]Yu G,Xu X,Klinger Y,et al.Fault-scarp features andcascading-rupture model for the Mw7.9 Wenchuan earthquake,eastern Tibetan plateau,China.Bull.Seismol.Soc.Am.,2010,100(5B):2590-2614.
[23]邵芸,谢酬,岳中琦等.青海玉树地震差分干涉雷达同震形变测量.遥感学报,2010,14(5):1029-1037.Shao Y,Xie C,Yue Z Q,et al.Co-seismic grounddeformation of Yushu Earthquake detected with D-InSARtechnique.Journal of Remote Sensing(in Chinese),2010,14(5):1029-1037.
[24]Knuepfer P L K.Implications of the characteristics of end-points of historical surface fault ruptures for the nature offault segmentation.U.S.G.S.Open-File Report,1989:89-135,193-228.
[25]Cunningham W D,Mann P.Tectonics of strike-sliprestraining and releasing bends.Geological Society,2007,290(1):1-12,doi:10.1144/SP290.1.
[26]Wells D L,Coppersmith K J.New empirical relationshipsamong magnitude,rupture length,rupture width,rupturearea,and surface displacement.Bull.Seismol.Soc.Am.,1994,84(4):974-1002.
[27]刁桂苓,王晓山,高国英等.以震源机制类型划分汶川、玉树地震构造块体归属.地球物理学报,2010,53(8):1778-1783.Diao G L,Wang X S,Gao G Y,et al.Tectonic blockattribution of Wenchuan and Yushu earthquakes distinguishedby focal mechanism type.Chinese J.Geophys.(in Chinese),2010,53(8):1778-1783.
[28]Xu X W,Wang F,Zheng R Z,et al.Late Quaternarysinistral slip rate along the Altyn Tagh fault and its structuraltransformation model.Science in China Series D:EarthSciences,2005,48(3):384-397.
[29]Fu B H,Awata Y.Displacement and timing of left-lateralfaulting in the Kunlun Fault Zone,northern Tibet,inferredfrom geologic and geomorphic features.Journal of AsianEarth Sciences,2007,29(2-3):253-265.
[30]Zhang Z J,Klemperer S L,Bai Z M,et al.Crustal structureof the Paleozoic Kunlun orogeny from an active-source seismicprofile between Moba and Guide in East Tibet,China.Gondwana Research,2011,19(4):944-1007,doi:10.1016/j.gr.2010.09.008.
[31]Zhang Z J,Wang Y H,Chen Y,et al.Crustal structureacross Longmenshan fault belt from passive source seismicprofiling.Geophysical Research Letter,2009,36:L17310.
[32]Fu B H,Shi P L,Guo H D,et al.Surface deformationrelated to the 2008 Wenchuan earthquake,and mountainbuilding of the Longmen Shan,eastern Tibetan Plateau.Journal of Asian Earth Sciences,2011,40(4):805-824,doi:10.1016/j.jseaes.2010.11.011.
[33]Zhang Z J,Yuan X H,Chen Y,et al.Seismic signature ofthe collision between the east Tibetan escape flow and theSichuan Basin.Earth and Planetary Science Letter,2010,292(3-4):254-264.
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