荥经-马边-盐津逆冲构造带断裂运动组合及地震分段特征
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摘要
逆冲构造带的分段性研究是评价该类发震构造地震危险性的基础工作。荥经-马边-盐津逆冲构造带是青藏高原东南边缘重要的NW向强震构造带,该构造带以逆冲错动为主要活动形式,其组合形式与逆冲强度存在南北差异。通过NE向横向断裂的构造地貌分析,发现横向断裂以右旋走滑活动为主,兼有倾滑活动。根据其与纵向断裂的交接关系,将横向断裂概括为横向分割断裂、横向撕裂断裂和横向转换断裂3种类型,讨论了3类横向断裂在逆冲构造带分段中所起的不同作用,进而将荥经-马边-盐津逆冲构造带分为独立的3段,并分析了各段的地震活动特征。研究表明,荥经-马边-盐津逆冲构造带以横向断裂为标志的3分段特点,既体现了段与段之间断裂活动强度、地震破裂强度与步调的差异,又体现了段内地震破裂步调的一致性,表明横向断裂在一定程度上控制了逆冲构造带的破裂分段,只是横向断裂的类型不同,其所起的作用也不同。
Segmentation of thrust fault zone is a basic problem for earthquake hazard evaluation. The Yingjing-Mabian-Yanjin thrust fault zone is an important seismic belt trending northwest in the southeast of Tibetan plateau. The longitudinal faults in the thrust zone are mainly of thrust slipping. The late Quaternary motion modes and displacement rates are quite different from north to south. Investigation on valleys across fault shows that the transverse faults are mainly of dextral strike-slipping with a bit dip displacement. Based on their connections with longitudinal faults, three types of transverse faults are generalized, namely, the separate fault, the transform fault and the tear fault, and their functions in the segmentation of the thrust fault zone are compared. As the result, the Yingjing-Mabian-Yanjin thrust fault zone is divided into three segments, and earthquakes of the three segments are compared. The trisection of Yingjing-Mabian-Yanjin thrust fault zone identified by transverse faults reflects, on one hand, the differences in slip rate, earthquake intensity and pace from each segment, and the coherence of earthquake rupturing pace on the other hand. It demonstrates that the transverse faults control the segmentation of thrust fault zone to a certain degree, and each type of the transverse faults plays a different role.
Segmentation of thrust fault zone is a basic problem for earthquake hazard evaluation. The Yingjing-Mabian-Yanjin thrust fault zone is an important seismic belt trending northwest in the southeast of Tibetan plateau. The longitudinal faults in the thrust zone are mainly of thrust slipping. The late Quaternary motion modes and displacement rates are quite different from north to south. Investigation on valleys across fault shows that the transverse faults are mainly of dextral strike-slipping with a bit dip displacement. Based on their connections with longitudinal faults, three types of transverse faults are generalized, namely, the separate fault, the transform fault and the tear fault, and their functions in the segmentation of the thrust fault zone are compared. As the result, the Yingjing-Mabian-Yanjin thrust fault zone is divided into three segments, and earthquakes of the three segments are compared. The trisection of Yingjing-Mabian-Yanjin thrust fault zone identified by transverse faults reflects, on one hand, the differences in slip rate, earthquake intensity and pace from each segment, and the coherence of earthquake rupturing pace on the other hand. It demonstrates that the transverse faults control the segmentation of thrust fault zone to a certain degree, and each type of the transverse faults plays a different role.
引文
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邓起东,张培震.1995.活动断裂分段研究的原则和方法(一)[A].见:国家地震局地质研究所编.现代地壳运动研究(6).北京:地震出版社.196—207.DENGQi dong,ZHANGPei zhen.1995.Principlesandmethodsforsegmentationofactivefaults(Ⅰ)[A].In:Insti tuteofGeology,StateSeismologicalBureau(ed).ResearchonRecentCrustalMovement(6).Seismological Press,Beijing.196—207(inChinese).
邓起东,冯先岳,张培震,等.2000.天山活动断裂[M].北京:地震出版社.302—321.DENGQi dong,FENGXian yue,ZHANGPei zhen,etal.2000.ActiveTectonicsofChineseTianshanMountains[M].SeismologicalPress,Beijing.302—321(inChinese).
丁国瑜,田勤俭,孔凡臣,等.1993.活断层分段:原则、方法及应用[M].北京:地震出版社.90—106.DINGGuo yu,TIANQin jian,KONGFan chen,etal.1993.SegmentationofActiveFault:Principle,MethodandAp plication[M].SeismologicalPress,Beijing.90—106(inChinese).
唐荣昌,韩渭宾.1993.四川活动断裂与地震[M].北京:地震出版社.138—150.TANGRong chang,HANWei bin.1993.ActiveFaultsandEarthquakesinSichuanProvince[M].SeismologicalPress,Beijing.138—150(inChinese).
王二七,孟庆任,陈智,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.WANGEr qi,MENGQing ren,CHENZhi,etal.2001.EarlyMesozoicleft lateralmovementalongtheLongmenShan Faultbeltanditstectonicimplications[J].EarthScienceFrontiers,8(2):375—384(inChinese).
张培震,邓起东,徐锡伟,等.1994.盲断层、“褶皱地震”与1906年马纳斯地震[J].地震地质,16(3):193—204.ZHANGPei zhen,DENGQi dong,XUXi wei,etal.1994.Blindthrust,foldingearthquake,andthe1906Manas earthquake,Xinjiang[J].SeismologyandGeology,16(3):193—204(inChinese).
张培震,毛凤英,常向东.1998.重大工程地震安全性评价中活动断裂分段的准则[J].地震地质,20(4):289—301.ZHANGPei zhen,MAOFeng ying,CHANGXiang dong.1998.Thecriteriaforactivefaultsegmentationinseismicsafetyassessmentofmajorengineering[J].SeismologyandGeology,20(4):289—301(inChinese).
张肇诚,罗兰格,李海华,等.1988.中国震例(1966—1975)[M].北京:地震出版社.155—177.ZHANGZhao cheng,LUOLan ge,LIHai hua,etal.1988.EarthquakeCasesinChina[M].SeismologicalPress,Bei jing.155—177(inChinese).
周荣军,唐荣昌,钱洪,等.1997.地震构造类比法的应用:以川东地区华蓥山断裂带为例[J].地震研究,20(3):316—322.ZHOURong jun,TANGRong chang,QIANHong,etal.1997.AnapplicationofseismotectonicanalogytotheHuaying shanFaultzoneineastSichuan[J].JournalofSeismologicalResearch,20(3):316—322(inChinese).
朱志澄.2004.构造地质学[M].武汉:中国地质大学出版社.173—191.ZHUZhi cheng.2004.StructuralGeology[M].ChinaUniversityofGeosciencesPress,Wuhan.173—191(inChi nese).
CaskySJ,WesnouskySG,ZhangP,etal.1996.Surfacefaultingofthe1954FairviewPeak(MS7.2)andDixieValley(MS6.8)earthquakes,CentralNevada[J].BullSeismSocAm,86(3):761—787.
CroneAJ,HallerKM.1991.Segmentationofbasinandrangenormalfaults:Examplesfromeast—centralIdahoand southwesternMontana[J].JStructGeol,13:151—164.
dePoloCM,ClarkDG,SlemmonsDB,etal.1991.HistoricalBasinandRangeProvincesurfacefaultingandfaultseg mentation[J].JStructGeol,13:123—136.
KnuepferPLK.1989.Implicationsofthecharacteristicsofend pointsofhistoricalsurfacefaultrupturesforthenature offaultsegmentation[R].U.S.G.S.Open Filereport.89—135,193—228.
SchwartzDP.1989.Paleoseismicity,persistenceofsegments,andtemporalclusteringoflargeearthquakes examples fromtheSanAndreas,Wasatch,andLostRiverfaultzones[R].U.S.G.S.Open FileReport.89—315,361—375.
SteinRS,YeatsRS.1989.Hiddenearthquake[J].ScientificAmerica,260(1):48—57.
ZhangP,SlemmonsDB,MaoF.1991.Geometricpattern,rupturetermination,andfaultsegmentationoftheDixie Valley PleasantValleyactivenormalfaultsystem,Nevada,USA[J].JStructGeol,13:165—176.
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