2001年东昆仑地震(Ms=8.1)不对称的同震地表破裂构造——单侧块体运动为主及青藏高原内部物质向东滑移的证据
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摘要
通过对 2 0 0 1年 11月 14日发生的东昆仑地震 (Ms=8.1)地表破裂带的野外考察 ,发现沿东昆仑断裂带发育一类不对称的同震地表破裂构造 :单侧垂直破裂带的张裂隙构造、不对称式拉分构造以及冻土层范围内的低角度逆冲构造。这些不对称的同震地表破裂构造不仅指示发震断裂为左行走滑 ,而且表明以断裂南侧块体向东运动为主、北侧块体向西甚微运动 (以地震前同地为参照系 )的运动学特征。与 GPS的观测数据结果所反映的运动特征基本一致 ,同时与不对称的区域稳定性相吻合。这种反映单侧块体运动为主的不对称同震地表破裂构造在大陆地震破裂带中是少有的 ,它的发现不仅表明东昆仑断裂以南的青藏高原内部物质向东滑移 ,而且由此认为自全新世以来其向东滑移的速率有可能约略小于 10～ 12 m m/ a,并同时指示断裂南侧相对于北侧为地震地质灾害更严重地域。
Field investigations show that the East Kunlun earthquake (Ms=8.1) on November 14th 2001 produced a type of asymmetrical co-seismic surface rupture structures, such as open-crack systems perpendicular to surface rupture zones, asymmetrical pull-apart structures and low-angle thrusts within frozen soil layers. These asymmetrical co-seismic surface rupture structures show that faults are left-lateral slipping and the southern sides of the faults moved eastward, i.e., the southern sides of the faults are the main active part. GPS data also show basically the same kinematics on the south (Tibet) and the north (the Qaidam Basin) sides of the faults. In addition, this kinematics results also accord with asymmetric district stability across the faults. The asymmetrical co-seismic rupture structures reflected a single-side movement along the active Kunlun Fault, and are an unwonted structure in typical interseismic structures, which indicate that the Kunlun Fault partitions its deformation into an eastward extrusion of Tibet to accommodate the continuing penetration of the Indian plate into the Eurasian plate, and the southern side of the Kunlun Fault moves eastward. The long-term eastward slip rate is determined to be about 10～12 mm/a or less, and the southern sides are more dangerous than the northern sides of the faults.
Field investigations show that the East Kunlun earthquake (Ms=8.1) on November 14th 2001 produced a type of asymmetrical co-seismic surface rupture structures, such as open-crack systems perpendicular to surface rupture zones, asymmetrical pull-apart structures and low-angle thrusts within frozen soil layers. These asymmetrical co-seismic surface rupture structures show that faults are left-lateral slipping and the southern sides of the faults moved eastward, i.e., the southern sides of the faults are the main active part. GPS data also show basically the same kinematics on the south (Tibet) and the north (the Qaidam Basin) sides of the faults. In addition, this kinematics results also accord with asymmetric district stability across the faults. The asymmetrical co-seismic rupture structures reflected a single-side movement along the active Kunlun Fault, and are an unwonted structure in typical interseismic structures, which indicate that the Kunlun Fault partitions its deformation into an eastward extrusion of Tibet to accommodate the continuing penetration of the Indian plate into the Eurasian plate, and the southern side of the Kunlun Fault moves eastward. The long-term eastward slip rate is determined to be about 10～12 mm/a or less, and the southern sides are more dangerous than the northern sides of the faults.
引文
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L inA,F uB,GuoJ,etal.2002.Co-seismic strike-slip and rupturelength produced by the2001Ms8.1centralKunlunearthquake.Science,296:2015～2017.
L uMing,XuXiwei,ChenWenbin,et al.2002.Investigation on theearthquake(M =8.1) in west ofKunlunPass.ChinaSeismology,18(1):117～118(inChinese withEnglishabstract).
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MolnarP,TapponnierP.1978.Active tectonics ofTibet.J.Geophys.Res.,83:5361～5375.
PeltzerG,SaucierF.1996.Present-day kinematics ofAsia derivedfrom geologic fault rates.J.Geophys.Res.,101:27943～27956.
RaheB,FerrillD A,MorrisA P.1998.Physical analog modeling ofpull-apart basin evolution.Tectonophysics,285:21～40.
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TapponierP,XuZhiqin,RogerF,et al.2001.Oblique stepwise riseand growth of theTibet plateau.Science,294:671～678.
Van derWoerdJ,RyersonF J,TapponnierP,et al.1998.Holoceneleft-slip rate determined by cosm ogenic surface dating on theXidatan segment of theKunlun fault(Qinghai,China).Geology,26:695～698.
Van derWoerdJ,RyersonF J,TapponnierP,et al.2000.Uniformslip-rate along theKunlun fault:Implications for seismicbehaviour and large-scale tectonics.Geophys.Res.L ett.,27:2353～2356.
Van derWoerdJ,MeriauxA S,KlingerY,et al.2002.The14November2001,Mw=7.8Kokoxili earthquake in northernTibet(Qinghai province,China).SeismologicalResearchLetters,73:125～135.
WangQ,ZhangP,Freym uellerJT,etal.2001.Present-day crustaldeformation inChina constrained byGlobalPositioningSystemmeasurements.Science,294:574～577.
XuZhiqin,L iHaibing,YangJingsui,et al.2001.ObliqueSubduction and the large scale transpressional zone in southernKunlunMountains.ActaGeologicaSinica,75(2):156～164(inChinese withEnglish abstract).
YeatsR S,SiehK,AllenC R.1997.TheGeology ofEarthquake.Oxford:OxfordU niv.Press.ZhaoGuoguang.1996.Quaternary faulting inNorthQinghai-TibetPlateau.ContinentalDynamics,(1):30～37.
党光明,王赞军.2002.青海昆仑山口西Ms8.1级地震地表破裂带特征与主要震害.地质通报,21(2):105～108.
顾功叙.1983.中国地震目录(1831BC-1969AD).北京,科学出版社.
陆鸣,徐锡伟,陈文斌,等.2002.昆仑山口西8.1级地震调查.中国地震,18(1):117～118.
青海地震局,中国地震局地壳应力研究所.1999.东昆仑活动断裂带北京:地震出版社.
任金卫,汪一鹏,吴章明,等.1999.青藏高原北部东昆仑断裂带第四纪活动特征和活动速率.见:中国地震局地震研究所编.活动断裂研究(7).北京:地震出版社,147～163.
王琪,张培震,牛之俊,等.2001.中国大陆现今地壳运动和构造变形.中国科学(D辑),31(7):529～536.
王琪,张培震,马宗.2002.中国大陆现今构造变形GPS观测数据与速度场.地学前缘,9(2):415～429.
徐锡伟,陈文彬,于贵华,等.2002.2001年11月14日昆仑山库赛湖地震(Ms8.1)地表破裂带的基本特征.地震地质,24(1):1～14.
许志琴,李海兵,杨经绥,等,2001.东昆仑山南缘大型转换挤压构造带和斜向俯冲.地质学报,75(2):156～164.
曾秋生.1999.青海地震综合研究.北京:地震出版社.
张培震,王琪,马宗晋.2002.青藏高原现今构造变形特征与GPS速度场.地学前缘,9(2):442～450.
中国地震局中国地震信息网.2001.“2001年青海(M:8.1)地震”(http://210.72.96.1/ focus-hot/ qingcmtcomp.htm)
AvouacJ P,TapponnierP.1993.Kinematic model of activedeformation inCentral-Asia.Geophys.Res.Lett.,20:895～898.
BasileC,BrunJP.1999.Transtensional faulting patterns rangingfrom pull-apart basins to transform continental margins:anexperim ental investigation.Journal ofStructuralGeology,21:23～37.
BasileC,MascleJ,PopoffM,et al.1993.TheIvoryCoast-Ghanatransform margin:a marginal ridge structure deduced fromseismic data.Tectonophysics,222:1～19.
ChenWenbin,XuXiwei,ZhangZhijian,et al.2001.Investigationon the surface ruptures of theKusai hu earthquake on14November2001in m arch withQinghai andXinjiangProvince,China.NorthwesternSeismologicalJournal,4:313～317(inChinese withEnglish abstract).
DangGuangming,WangZanjun.2002.Characteristics of thesurface rupture zone and main seism ic hazards caused by theMs8.1earthquake west of theKunlun passChina-Constraintson the regional stability of theQinghai-TibetPlateau.GeologicalBulletin ofChina,2:105～108(inChinese withEnglish abstract).
FreymuellerJ,WangQ.2003.Asymmetric postseismicdeformation following the2001kokoxili earthquake requiresheterogeneity in material properties.EGS-AGU -EUG JointAssem bly,GeophysicalResearchAbstracts,Volume5.
L iH,QiX,ZhuY,YangJ,KlingerY,TapponnierP,Van derWoerdJ.2003.Coseismic ruptures of the14/11/2001,Mw=7.8Kokoxili earthquake nearHongshuiGou.EGS-AGU -EUGJointAssembly,GeophysicalResearchAbstracts,Volume5.L iHaibing,XuZhiqin,ChenWen.1996a.Deformational featuresand tectonic evolution of theSouthKunlun strike-slip shearzone,WastKunlunMountains.ActaGeoscientiaSinica,SpecialIssue:16～21.
L iHaibing,XuZhiqin,ChenWen.1996b.The southern marginstrike-slip fault zone of theEastKunlunMountains:Anim portant consequence from intracontinental deformation.ContinentalDynamics,1:146～155.
L iL ,ChenY.2002.Preliminary report on theMs8.1Kokoxili(Qinghai,China) earthquake of14November2001.Episodes,25:95～99.
L inA,F uB,GuoJ,etal.2002.Co-seismic strike-slip and rupturelength produced by the2001Ms8.1centralKunlunearthquake.Science,296:2015～2017.
L uMing,XuXiwei,ChenWenbin,et al.2002.Investigation on theearthquake(M =8.1) in west ofKunlunPass.ChinaSeismology,18(1):117～118(inChinese withEnglishabstract).
MolnarP,TapponnierP.1975.Cenozoic tectonics ofAsia:Effects ofa continental collision.Science,189:419～426.
MolnarP,TapponnierP.1978.Active tectonics ofTibet.J.Geophys.Res.,83:5361～5375.
PeltzerG,SaucierF.1996.Present-day kinematics ofAsia derivedfrom geologic fault rates.J.Geophys.Res.,101:27943～27956.
RaheB,FerrillD A,MorrisA P.1998.Physical analog modeling ofpull-apart basin evolution.Tectonophysics,285:21～40.
ShenZ,ZengY,WangM,et al.2003.Postseismic deformationmodeling of the2001kokoxili earthquake,westernChina.EGS-AGU-EUG JointAssembly,GeophysicalResearchAbstracts,Volume5.
TapponierP,MolnarP.1977.Active faulting and tectonics inChina.J.Geophys.Res.,82:2905～2930.
TapponierP,XuZhiqin,RogerF,et al.2001.Oblique stepwise riseand growth of theTibet plateau.Science,294:671～678.
Van derWoerdJ,RyersonF J,TapponnierP,et al.1998.Holoceneleft-slip rate determined by cosm ogenic surface dating on theXidatan segment of theKunlun fault(Qinghai,China).Geology,26:695～698.
Van derWoerdJ,RyersonF J,TapponnierP,et al.2000.Uniformslip-rate along theKunlun fault:Implications for seismicbehaviour and large-scale tectonics.Geophys.Res.L ett.,27:2353～2356.
Van derWoerdJ,MeriauxA S,KlingerY,et al.2002.The14November2001,Mw=7.8Kokoxili earthquake in northernTibet(Qinghai province,China).SeismologicalResearchLetters,73:125～135.
WangQ,ZhangP,Freym uellerJT,etal.2001.Present-day crustaldeformation inChina constrained byGlobalPositioningSystemmeasurements.Science,294:574～577.
XuZhiqin,L iHaibing,YangJingsui,et al.2001.ObliqueSubduction and the large scale transpressional zone in southernKunlunMountains.ActaGeologicaSinica,75(2):156～164(inChinese withEnglish abstract).
YeatsR S,SiehK,AllenC R.1997.TheGeology ofEarthquake.Oxford:OxfordU niv.Press.ZhaoGuoguang.1996.Quaternary faulting inNorthQinghai-TibetPlateau.ContinentalDynamics,(1):30～37.
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