西藏中部申扎—定结地堑系北段中新世以来构造地貌学研究
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摘要
利用ETM遥感影像与30m分辨率的ASTERDEM数据,构建申扎—定结地堑系北段遥感影像三维数字高程模型,结合野外地质地貌调查结果,对地堑系地貌特征进行总体分析。并根据对主要断裂的产状和活动性野外调查与活动断裂展布的遥感解译结果,认为地堑系由一条东倾的铲式主要断裂和一系列同倾向和反倾向的次级断裂组成的半地堑构造。基于半地堑系模式,将地堑系简化成书斜式模型,根据地堑的沉降量和地堑宽度值,计算地堑系的滑脱面深度在3.6～9.7km之间,因此地堑中地震震源深度也多集中于滑脱面附近。最后探讨地堑的形成机制,表明在印度板块的挤压作用下,高原上地壳与下地壳发生应力解耦,上地壳在重力作用下,向南向东发生滑脱,形成东倾的半地堑构造。
ETM remote sensing image and 30 m resolution ASTER DEM data are treated using ArcGIS,and three-dimensional digital elevation model of the northern segment of Shenzha-Dingjie graben with remote sensing image is built,combined with field investigattion,the overall of landscape characteristics of the graben is analysised.On the base of field observation of the main faults,as well as the spreading of graben's fault from remote sensing interpretation,we found that the faults in half-graben is composed by a east dip major fault with a series of synthetic sub-faults and antithetic sub-faults.Based on half-graben system model,a simple book oblique model is used to calculate the depth of detachment surface and the magnitude of stretch in the graben system.The depth between 3.6~9.7 km is basically consistent to the focal depth in the region,which prove that seismic activity concentrated in the vicinity of the detachment surface.Finally,the graben formation mechanism is discussed.The stress of upper crust is decoupled with lower crust's due to Indian plate extrusion,and the upper crust moves south and east from gravity,thus the half-graben dip east.
ETM remote sensing image and 30 m resolution ASTER DEM data are treated using ArcGIS,and three-dimensional digital elevation model of the northern segment of Shenzha-Dingjie graben with remote sensing image is built,combined with field investigattion,the overall of landscape characteristics of the graben is analysised.On the base of field observation of the main faults,as well as the spreading of graben's fault from remote sensing interpretation,we found that the faults in half-graben is composed by a east dip major fault with a series of synthetic sub-faults and antithetic sub-faults.Based on half-graben system model,a simple book oblique model is used to calculate the depth of detachment surface and the magnitude of stretch in the graben system.The depth between 3.6~9.7 km is basically consistent to the focal depth in the region,which prove that seismic activity concentrated in the vicinity of the detachment surface.Finally,the graben formation mechanism is discussed.The stress of upper crust is decoupled with lower crust's due to Indian plate extrusion,and the upper crust moves south and east from gravity,thus the half-graben dip east.
引文
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[20]姜明明,周仕勇,佟啸鹏,等.藏南地区中深源地震精确定深研究及其地球动力学含义[J].地球物理学报,2009,52(9):2237-2244.
[21]钟大赉,丁林.青藏高原隆起过程及其机制探讨[J].中国科学(D辑),1996,26:289-295.
[22]Zhang P Z,Shen Z,Bürgmann R,et al.Continuous deformation of the Tibetan Plateau fromglobal positioning systemdata[J].Geology,2004,32(9):809-812.
[23]张培震,王琪,马宗晋.青藏高原现今构造变形特征与GPS速度场[J].地学前缘,2002,9(2):442-450.
[2]Burehfiel B C,Royden L H.North-south extension withinthe convergent Himalayan region[J].Ge-ology,1985,13:679-682.
[3]England P C,Houseman G A.The mechanics of the Tibetan Plateau[J].Phil Thns R SoeLond,1986,326:301-320.
[4]曹圣华,李德威,余忠珍,等.西藏冈底斯当惹雍错—许如错南北向地堑的特征及成因[J].中国地质大学学报(地球科学),2009,34(6):914-920.
[5]Armijo R,Tapponnier P,Han T L.Late Cenozoic right-lateral strike-slip faultingin southern Tibet[J].J Geophys Res,1989,94:2787-2838.
[6]Armijo R,Tapponnier P,Mercier J L,et al.Quaternary extensionin southern Tibet:field observa-tions and tectonic implications[J].J Geophys Res,1986,91:13803-13872.
[7]Le Fort P.Manasluleueogranite,a collisional signature of the Himalaya,a model for its genesis and emplacement[J].J Geo Phys Res,1981,86:10545-10568.
[8]Blisniuk P M,Hacker B R,Glodny J.Normal faulting in central Tibet since at least13.5Myr ago[J].Nature,2001,412(6847):628-632.
[9]Yin A,Paul A.Kapp,Michael A.Murphy,Craig E.Manning.Significant late Neogene east-west extensionin northern Tibet[J].Geology,1999,27:787-790.
[10]Taylor M,Peltzer G.Current slip rates on conjugate strike-slipfaults in central Tibet using synthet-ic aperture radar interferometry[J].J Geophy Res,2006111(B12402,doi:10.1029/2005JB004014).
[11]Taylor M,Yin A,Ryerson F J,et al.Conjugate strike-slip faulting along the Bangong-Nujiang su-ture zone accommodates coeval east-west extension and north-south shortening in the interior of the Tibetan Plateau[J].Tectonics,2003,22(4):1044,doi:10.1029/2002TC001361,2003.
[12]Coleman M,Hodges K.Evidence for Tibetan Plateau uplift before14Myr age froma new minimum age for east-west extension[J].Nature,1995,374:49-52.
[13]Searle MP.The rise and fall of Tibet[J].Nature,1995,347:17-18.
[14]张进江,丁林,钟大赉,等.喜马拉雅平行于造山带伸展:是垮塌的标志还是挤压隆升过程的产物-[J].科学通报,1999,44:2011-2036.
[15]张进江,郭磊,丁林.申扎—定结正断层体系中、南段构造特征及其与藏南拆离系的关系[J].科学通报,2002,47(10):738-743.
[16]Yin A,Harrison T M.Geologic evolution of the Himalayan-Tibetan orogen[J].Annu Rev Earth Planet Sci,2000,28:211-280.
[17]Liu-Zeng J,Tapponnier P,Gaudemer Y,et al.Quantifyinglandscape differences across the Tibetan plateau:Implications for topographic relief evolution[J].J Geophys Res,2008,113:1-26.
[18]吴章明,曹忠权,申屠炳明,等.西藏申扎南发现地震地表破裂[J].地震地质,1990,12(4):317-318.
[19]Liang X,Zhou S,Chen YJ,et al.Earthquake distributionin southern Tibet and its tectonic impli-cations[J].J Geophys Res,2008,113,doi:10.1029/2007JB005101.
[20]姜明明,周仕勇,佟啸鹏,等.藏南地区中深源地震精确定深研究及其地球动力学含义[J].地球物理学报,2009,52(9):2237-2244.
[21]钟大赉,丁林.青藏高原隆起过程及其机制探讨[J].中国科学(D辑),1996,26:289-295.
[22]Zhang P Z,Shen Z,Bürgmann R,et al.Continuous deformation of the Tibetan Plateau fromglobal positioning systemdata[J].Geology,2004,32(9):809-812.
[23]张培震,王琪,马宗晋.青藏高原现今构造变形特征与GPS速度场[J].地学前缘,2002,9(2):442-450.
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