东昆仑断裂带东部塔藏断裂地震地表破裂特征及其构造意义
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摘要
东昆仑断裂带作为青藏高原中东部的巴颜喀拉地块北缘边界断裂带,研究其强震破裂行为对于认识断裂带活动性及分析川西北地区未来地震危险性具有重要意义。通过沿断裂发育的大量断错地貌勘查、典型微地貌DGPS测量及样品年代测定,认为东昆仑断裂带向东的强震活动性延伸至若尔盖盆地北侧,即东昆仑断裂带东部塔藏断裂的罗叉段。此段在卫星影像上呈清晰的灰黑色、灰黄色线性条带,地震形变带主要表现为断层陡坎、坡中谷、冲沟和阶地位错、植物异常呈线性分布、跌水、断层泉、断塞塘以及伴随地表错动而出现的滑坡、垮塌和倒石堆。这些破裂现象沿先存断层断续分布,组成长约50km的"L"形地震形变带。断裂活动造成冲沟和阶地左行运动,位错量主要集中在5.5～6.0m、18～23m、68～75m和200～220m范围。最近地震发生在(340±30)～(500±30)BP间,宏观震中位于本多村西北5～7km,震级为MW7.3左右,同震位移最大值为6m,水平位错量为5.5～6.0m,垂直位错量一般为0.2～0.5m,其比例为51～101。对地震形变带中的各种变形遗迹和地震地表破裂特征的研究表明,塔藏断裂是这次地震的发震构造。确定了塔藏断裂为全新世活动断层,近期断层在压剪切作用控制下以左行运动为主,兼有少量逆冲分量,同东昆仑断裂带其他段的活动性质相似,认为东昆仑断裂带延伸至若尔盖盆地北侧,研究结果支持"大陆逃逸"模型。
The East Kunlun fault zones are located in the northern margin of the Bayanhar block.Investigation of earthquake rupture behaviors of these fault zones is helpful for future seismic risk estimation for northwest Sichuan.We carried out a number of field geological investigation,typical micro-topography DGPS measurement and sample dating.Our results show that earthquake activities of the East Kunlun fault zones extend to the north bound of the Zoige basin.This part has been named Luocha segment,which belonged to the Tazang fault.Satellite images for Luocha segment are clear on the gray strips.The earthquake rupture zones are represented mainly by fault scarp,slope in the valley,gully and terraces dislocation,plant distribution in linear,plunge,fault springs,broken plug pond,landslide,collapsed and talus.These phenomena are distributed along the fault and formed an ~50 km long inverse "L-shaped" deformation strip.Fault activities produced gullies and left movement of terraces.Horizontal dislocations are in the range of 5.5~6 m,18~23 m,68~75 m,200~220 m respectively.An earthquake happened recently between 340±30~500±30 BP,its macro-epicenter was located 5~7 kms northwest from the Benduo village,magnitude MW7.3~7.4,with a maximum of 6 m coseismic displacement,horizontal dislocation 5.5~6 m,vertical dislocation 0.2~0.5 m.These phenomena show that the Tazang fault was the causative fault of the earthquake and raptured in Holocene.The fault has been controlled by compressive shear recently and shows horizontal movement with slight thrust components,similar to other segments of the East Kunlun fault zones.The results supports the "mainland escape" model.
The East Kunlun fault zones are located in the northern margin of the Bayanhar block.Investigation of earthquake rupture behaviors of these fault zones is helpful for future seismic risk estimation for northwest Sichuan.We carried out a number of field geological investigation,typical micro-topography DGPS measurement and sample dating.Our results show that earthquake activities of the East Kunlun fault zones extend to the north bound of the Zoige basin.This part has been named Luocha segment,which belonged to the Tazang fault.Satellite images for Luocha segment are clear on the gray strips.The earthquake rupture zones are represented mainly by fault scarp,slope in the valley,gully and terraces dislocation,plant distribution in linear,plunge,fault springs,broken plug pond,landslide,collapsed and talus.These phenomena are distributed along the fault and formed an ~50 km long inverse "L-shaped" deformation strip.Fault activities produced gullies and left movement of terraces.Horizontal dislocations are in the range of 5.5~6 m,18~23 m,68~75 m,200~220 m respectively.An earthquake happened recently between 340±30~500±30 BP,its macro-epicenter was located 5~7 kms northwest from the Benduo village,magnitude MW7.3~7.4,with a maximum of 6 m coseismic displacement,horizontal dislocation 5.5~6 m,vertical dislocation 0.2~0.5 m.These phenomena show that the Tazang fault was the causative fault of the earthquake and raptured in Holocene.The fault has been controlled by compressive shear recently and shows horizontal movement with slight thrust components,similar to other segments of the East Kunlun fault zones.The results supports the "mainland escape" model.
引文
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[11]闻学泽,杜方,张培震,等.巴颜喀拉块体北和东边界大地震序列的关联性与2008年汶川地震[J].地球物理学报,2011,54(3):706-716.
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[13]国家地震局震害防御司(编).中国历史强震目录(公元前23世纪—公元1911年)[M].北京:地震出版社,1995.
[14]刘光勋.东昆仑活动断裂带及其强震活动[J].中国地震,1996,12(2):119-126.
[15]青海省地震局,中国地震局地壳应力研究所.东昆仑活动断裂带[M].北京:地震出版社,1999.
[16]中国地震局震害防御司(编).中国历史强震目录(公元前1912—公元1990年,MS≥4.7)[M].北京:中国科学技术出版社,1999.
[17]Peltzer G,CrampéF,King G.Evidence of Nonlinear Elasticity of the Crust from the MW7.6Man yi(Tibet)Earthquake[J].Science,1999,286:272-276.
[18]Guo J,Lin A,Sun G,et al.Surface Ruptures Associated with the 1937 M7.5Tuosuo Lake and the1963 M7.0Alake Lake Earthquakes and the Paleoseismicity along the Tuosuo Lake Segment of theKunlun Fault,Northern Tibet[J].Bulletin of the Seismological Society of America,2007,97:474-496.
[19]陈杰,陈宇坤,丁国瑜,等.2001年昆仑山口西MS8.1地震地表同震位移分布特征[J].地震地质,2004,26(3):378-384.
[20]Van Der Woerd J,Tapponnier P,Ryerson FJ,et al.Uniform post glacial slip-rate along the central600km of the Kunlun Fault(Tibet),from Al-26,Be-10,and C-14dating of riser offsets,and climat-ic origin of the regional morphology[J].Geophysical Journal International,2002,148:356-388.
[21]Kidd W S F,Molnar P.Quaternary and active faulting observed on the 1985Academia Sinica-RoyalSociety Geotraverse of Tibet.Philosophical Transactions of the Royal Society of London[J].Se-riesA,Mathematical and Physical Sciences,1988,327:337-363.
[22]Zhang P Z,Shen Z,Wang M,et al.Continuous deformation of the Tibetan Plateau from global po-sitioning systemdata[J].Geology,2004,32:809-812.
[23]任金卫,汪一鹏,吴章明,等.青藏高原北部库玛断裂东、西大滩段全新世地震形变带及其位移特征和水平滑动速率[J].地震地质,1993,15(3):285-288.
[24]马寅生,施炜,张岳桥,等.东昆仑活动断裂带玛曲段活动特征及其东延[J].地质通报,2005,24(1):30-36.
[25]何文贵,袁道阳,熊振,等.东昆仑断裂带东段玛曲断裂新活动特征及全新世滑动速率研究[J].地震,2006,26(3):67-75.
[26]Kirby E,Harkins N,Wang E,et al.SliprategradientsalongtheeasternKunlunfault[J].Tectonics,2007,26:TC2010.
[27]Lin A,Guo J.Nonuniform Slip Rate and Millennial Recurrence Interval of Large Earthquakes alongthe Eastern Segment of the Kunlun Fault,Northern Tibet[J].Bulletin of the Seismological Societyof America,2008,98:2 866-2 878.
[28]李陈侠.东昆仑断裂带东段(玛沁—玛曲)晚第四纪长期滑动习性研究[D].中国地震局地质研究所,2009.
[29]Xu X,Yu G,Klinger Y,et al.Reevaluation of surface rupture parameters and faulting segmentationof the 2001Kunlunshan earthquake(MW7.8),northern Tibetan Plateau,China[J].J Geophys Res,2006,111:B05316.
[30]肖振敏,刘光勋,王焕贞,等.青海花石峡地震形变带的初步研究[J].中国地震,1988.4(1):25-36.
[31]张军龙.汶川MS8级地震形成的擦痕形迹及其意义探讨[J].地学前缘,2009,16(3):294-305.
[32]Junlong Z,Changyun C,Chaozhong H,et al.Surface Rupture and Coseismic Displacement of theMS7.1Yushu Earthquake[J].Earthquake Research in China,2011.25(2):10-23.
[33]丁国瑜.关于公元649年临汾地震的讨论[J].中国地震,1998,14(3):38-42.
[34]任金卫,李玶.四川西昌1850年地震地表破裂特征研究[J].地震地质,1993,15(3):97-106.
[35]徐锡伟,闻学泽,陈桂华,等.巴颜喀拉地块东部龙日坝断裂带的发现及其大地构造意义[J].中国科学(D辑:地球科学),2008,38(5):529-542.
[36]Togo T,Shimamoto T,Ma S,Hirose T.High-velocity frictional behavior of Longmenshan faultgouge from Hongkou outcrop and its implications for dynamic weakening of fault during the 2008Wenchuan earthquake.Earthquake Science,2011,24(3):267-281.
[37]郭增建,秦保燕,徐文耀,等.震源孕育模式的初步讨论[J].地球物理学报,1973,16(1):43-48.
[38]丁国瑜,田勤俭,孔凡臣,等.活断层分段原则、方法及应用[M].北京:地震出版社,1993.
[39]周蕙兰.中国历史大地震的矩震级[J].地球物理学报,1984,27(4):360-370.
[40]邓起东,于桂华,叶文华.地震地表破裂与震级关系的研究[A].活动断裂研究[C].北京:地震出版社,1992.247-264.
[41]Wells D L,Coppersmith K J.New empirical relationships among magnitude,rupture length,rup-ture width,rupture area,and surface displacement[J].Bulletin of the Seismological Society of A-merica,1994,84:974-1 002.
[2]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[J].中国科学(D辑):地球科学,2008.38(7):785-796.
[3]徐锡伟,闻学泽,叶建青,等.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,2008,30(2):597-629.
[4]张培震,徐锡伟,闻学泽,等.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,2008,51(4):1 066-1 073.
[5]张军龙,申旭辉,徐岳仁,等.汶川8级大地震的地表破裂特征及分段[J].地震,2009,29(3):149-154.
[6]张军龙,陈长云,胡朝忠,等.玉树MS7.1地震地表破裂带及其同震位移分布[J].地震,2010,30(1):1-12.
[7]任金卫,王敏.GPS观测的2001年昆仑山口西MS8.1地震地壳变形[J].第四纪研究,2005,25(1):34-44.
[8]张军龙,田勤俭,张小龙,等.Dgps方法在新构造研究中的应用探讨[J].地学前缘,2008,15(4):290-297.
[9]张军龙,田勤俭,李智敏,等.差分gps方法在城市活断层探测中的应用探讨[J].地震,2007,27(4):74-82.
[10]邓起东,冉勇康,杨晓平,等.中国活动构造图[M].北京:地震出版社,2007.
[11]闻学泽,杜方,张培震,等.巴颜喀拉块体北和东边界大地震序列的关联性与2008年汶川地震[J].地球物理学报,2011,54(3):706-716.
[12]顾功叙(主编).中国地震目录[M].北京:科学出版社,1983.
[13]国家地震局震害防御司(编).中国历史强震目录(公元前23世纪—公元1911年)[M].北京:地震出版社,1995.
[14]刘光勋.东昆仑活动断裂带及其强震活动[J].中国地震,1996,12(2):119-126.
[15]青海省地震局,中国地震局地壳应力研究所.东昆仑活动断裂带[M].北京:地震出版社,1999.
[16]中国地震局震害防御司(编).中国历史强震目录(公元前1912—公元1990年,MS≥4.7)[M].北京:中国科学技术出版社,1999.
[17]Peltzer G,CrampéF,King G.Evidence of Nonlinear Elasticity of the Crust from the MW7.6Man yi(Tibet)Earthquake[J].Science,1999,286:272-276.
[18]Guo J,Lin A,Sun G,et al.Surface Ruptures Associated with the 1937 M7.5Tuosuo Lake and the1963 M7.0Alake Lake Earthquakes and the Paleoseismicity along the Tuosuo Lake Segment of theKunlun Fault,Northern Tibet[J].Bulletin of the Seismological Society of America,2007,97:474-496.
[19]陈杰,陈宇坤,丁国瑜,等.2001年昆仑山口西MS8.1地震地表同震位移分布特征[J].地震地质,2004,26(3):378-384.
[20]Van Der Woerd J,Tapponnier P,Ryerson FJ,et al.Uniform post glacial slip-rate along the central600km of the Kunlun Fault(Tibet),from Al-26,Be-10,and C-14dating of riser offsets,and climat-ic origin of the regional morphology[J].Geophysical Journal International,2002,148:356-388.
[21]Kidd W S F,Molnar P.Quaternary and active faulting observed on the 1985Academia Sinica-RoyalSociety Geotraverse of Tibet.Philosophical Transactions of the Royal Society of London[J].Se-riesA,Mathematical and Physical Sciences,1988,327:337-363.
[22]Zhang P Z,Shen Z,Wang M,et al.Continuous deformation of the Tibetan Plateau from global po-sitioning systemdata[J].Geology,2004,32:809-812.
[23]任金卫,汪一鹏,吴章明,等.青藏高原北部库玛断裂东、西大滩段全新世地震形变带及其位移特征和水平滑动速率[J].地震地质,1993,15(3):285-288.
[24]马寅生,施炜,张岳桥,等.东昆仑活动断裂带玛曲段活动特征及其东延[J].地质通报,2005,24(1):30-36.
[25]何文贵,袁道阳,熊振,等.东昆仑断裂带东段玛曲断裂新活动特征及全新世滑动速率研究[J].地震,2006,26(3):67-75.
[26]Kirby E,Harkins N,Wang E,et al.SliprategradientsalongtheeasternKunlunfault[J].Tectonics,2007,26:TC2010.
[27]Lin A,Guo J.Nonuniform Slip Rate and Millennial Recurrence Interval of Large Earthquakes alongthe Eastern Segment of the Kunlun Fault,Northern Tibet[J].Bulletin of the Seismological Societyof America,2008,98:2 866-2 878.
[28]李陈侠.东昆仑断裂带东段(玛沁—玛曲)晚第四纪长期滑动习性研究[D].中国地震局地质研究所,2009.
[29]Xu X,Yu G,Klinger Y,et al.Reevaluation of surface rupture parameters and faulting segmentationof the 2001Kunlunshan earthquake(MW7.8),northern Tibetan Plateau,China[J].J Geophys Res,2006,111:B05316.
[30]肖振敏,刘光勋,王焕贞,等.青海花石峡地震形变带的初步研究[J].中国地震,1988.4(1):25-36.
[31]张军龙.汶川MS8级地震形成的擦痕形迹及其意义探讨[J].地学前缘,2009,16(3):294-305.
[32]Junlong Z,Changyun C,Chaozhong H,et al.Surface Rupture and Coseismic Displacement of theMS7.1Yushu Earthquake[J].Earthquake Research in China,2011.25(2):10-23.
[33]丁国瑜.关于公元649年临汾地震的讨论[J].中国地震,1998,14(3):38-42.
[34]任金卫,李玶.四川西昌1850年地震地表破裂特征研究[J].地震地质,1993,15(3):97-106.
[35]徐锡伟,闻学泽,陈桂华,等.巴颜喀拉地块东部龙日坝断裂带的发现及其大地构造意义[J].中国科学(D辑:地球科学),2008,38(5):529-542.
[36]Togo T,Shimamoto T,Ma S,Hirose T.High-velocity frictional behavior of Longmenshan faultgouge from Hongkou outcrop and its implications for dynamic weakening of fault during the 2008Wenchuan earthquake.Earthquake Science,2011,24(3):267-281.
[37]郭增建,秦保燕,徐文耀,等.震源孕育模式的初步讨论[J].地球物理学报,1973,16(1):43-48.
[38]丁国瑜,田勤俭,孔凡臣,等.活断层分段原则、方法及应用[M].北京:地震出版社,1993.
[39]周蕙兰.中国历史大地震的矩震级[J].地球物理学报,1984,27(4):360-370.
[40]邓起东,于桂华,叶文华.地震地表破裂与震级关系的研究[A].活动断裂研究[C].北京:地震出版社,1992.247-264.
[41]Wells D L,Coppersmith K J.New empirical relationships among magnitude,rupture length,rup-ture width,rupture area,and surface displacement[J].Bulletin of the Seismological Society of A-merica,1994,84:974-1 002.
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