利用GPS观测研究拉萨地块中段现今地壳运动与变形
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摘要
以拉萨地块中段铁路沿线GPS局域网2005—2007年高精度观测资料为依据,结合区域活动断裂构造、地形地貌特点和历史强震活动,研究了拉萨地块中段铁路沿线活动构造区域现今地壳运动变形与主要断裂活动的一些特征。初步结果显示:1)研究区现今水平运动速度方向呈北东-北东东向,与印度板块向北碰撞引起青藏高原总体运动背景一致,反映了现今地壳受到近南北方向水平挤压和物质向东流动双重水平动力的联合作用;2)区域视应变分布表现出不同地段变形方式的差异,与地壳伸展变形方式存在密切关系,反映了新构造时期以来盆地的拉张伸展变形与山地受压隆起的"盆-山"构造活动分异;3)区内北西-北西西向展布的F76、F67、F503条断裂活动速率自南向北递减明显,其与北东-北北东走向的断裂F73、F65交汇部位及其附近的视应变高值分布区中,历史地震活动非常强烈,反映了构造活动变形的继承性。
On the basis of the GPS measurement data in 2005—2007 along the railway in central Lhasa block,combining with the parameters of regional active faults and topographic-geomorphic character and historical strong earthquake,the characteristics of present-day crustal movement and deformation and main fault activity along the railway in the middle of Lhasa block are analyzed.The conclusions are drawn as follows.1)The present-day horizontal movement direction of the studied area is WE-NEE,consistent with the Tibetan plateau movement background by the northward collision of the India block that reflects the joint action of the horizontal dynamics from both the north-southward horizontal compression and the eastward matter flow.2)The regional apparent strain distribution manifests itself in the different mode in different zone that closely related to the crust extension deformation made and reflects the divergence of the basin extension deformation with the 'basin-mountain' tectonic activity of pressed and rise mountainous region.3)Active velocities of the faults:F76,F67 and F50 evidently descent from S to N,in the spaces that they intersect with the NE-NNE faults F73 and F65 and their adjant area of high apparent strain distribution the historical seismic activity was very strong it reflects the inherit of tectonic activity and deformation.
On the basis of the GPS measurement data in 2005—2007 along the railway in central Lhasa block,combining with the parameters of regional active faults and topographic-geomorphic character and historical strong earthquake,the characteristics of present-day crustal movement and deformation and main fault activity along the railway in the middle of Lhasa block are analyzed.The conclusions are drawn as follows.1)The present-day horizontal movement direction of the studied area is WE-NEE,consistent with the Tibetan plateau movement background by the northward collision of the India block that reflects the joint action of the horizontal dynamics from both the north-southward horizontal compression and the eastward matter flow.2)The regional apparent strain distribution manifests itself in the different mode in different zone that closely related to the crust extension deformation made and reflects the divergence of the basin extension deformation with the 'basin-mountain' tectonic activity of pressed and rise mountainous region.3)Active velocities of the faults:F76,F67 and F50 evidently descent from S to N,in the spaces that they intersect with the NE-NNE faults F73 and F65 and their adjant area of high apparent strain distribution the historical seismic activity was very strong it reflects the inherit of tectonic activity and deformation.
引文
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12王琪,等,中国大陆现今地壳运动与构造变形[J].中国科学(D辑),1998,31(7):163-172.(Wang Qi,et al.Current current crustal movement in Chinese mainland[J].Acta Seismologica Sinica,2003,25(5):453-464)
13江在森,等.昆仑山口西Ms8.1地震前区域构造变形背景[J].中国科学(D辑),2000,33(增刊):163-172.(Jiang Zaisen,et al.Horizntal strain field and tectonic de-formation of China mainland revealed by preliminary GPS result[J].Chinese Journal of Geophysics,2003,46(3):352-358)
2张培震,王琪,马宗晋.青藏高原现今构造特征与GPS速度场[J].地学前缘,2002,9(2):442-450.(Zhang Peizhen,Wang Qi and Ma Zongjin.Gps velocity field and active crustal deformation in and around the Qinghai-Tibet plateau[J].Earth Science Frontiers,2002,9(2),442-450)
3赖锡安,等.中国大陆现今地壳运动[M].北京:地震出版社,2004.(Lai Xian,et al.Present-day crustal movement in china constrained[M].Beijing:Seismological Press,2004)
4程万正,等.川滇地块的震源力学机制、运动速率和活动方式[J].地震地质,2003,(1),71-87.(Cheng Wanzheng,et al.Focal mechanisms,displacement rate and mode of motion of the Sichuan-Yunnan block[J].Seismolo-gy and Geology,2003,(1),71-87)
5吴珍汉,等.青藏铁路沿线断裂活动的灾害效应[J].现代地质,2003,17(1):1-6.(Wu Zhenhan,et al.Hazard effects of active faulting along the golmud-Lhasa railway across the Tibetan Plateau[J].Geoseience,2003,17(1):1-6)
6吴珍汉,等.青藏高原腹地的地壳形变与构造地貌形成演化过程[M].北京:地质出版社,2003.(Wu Zhenhan,etal.Crust deformation and tectonic-geomorphic evolution of the central Tibetan Plateau[M].Beijing:Geological Press,2003)
7李延兴,等.中国大陆活动地块的运动与应变状态[J].中国科学(D辑),2001,33(增刊):65-68.(Li Yanxing,et al.The state of motion and strain of activity plot in the main-land of China[J].Seience in China,Ser.D,2001,33(sup.):65-68)
8江在森,等.地形变资料求解应变值的尺度相对性问题研究[J].地震学报,2000,22(4):352-359.(Jiang Zaisen,et al.Study on scale dependence of strain value obtained from crustal deformation data[J].Acta Seismologica Sinica,2000,22(4):352-359)
9江在森,等.GPS技术应用于我国地壳运动研究的方法及初步结果[J].地学前缘,2003,22(4):352-359.(Jiang Zaisen,et al.Study on scale dependence of strain value ob-tained from crustal deformation data[J].Acta Seismologica Sinica,2000,22(4):352-359)
10赵文津,等.INDEPTH项目组.喜马拉雅山及雅鲁藏布江缝合带深部结构与构造研究[M].北京:地质出版社,2001.(Zhao Wenjin,et al.Seismic imaging of the subduc-ting Indian lithosphere beneath North Tibet[J].Acta Ge-osicientia Sinica,2004,25(1),1-10)
11张培震,等.青藏高原三维变形运动随时间的变化[A].见:现代地壳运动与地球动力学研究[C].北京:地震出版社,2001,88-105.(Zhang Peizhen,et al.Kinematics of present-day tectonic deformation of the Tibetan Plateau and its vicinities[J].Seismology and Geology,2004,26(3),367-377)
12王琪,等,中国大陆现今地壳运动与构造变形[J].中国科学(D辑),1998,31(7):163-172.(Wang Qi,et al.Current current crustal movement in Chinese mainland[J].Acta Seismologica Sinica,2003,25(5):453-464)
13江在森,等.昆仑山口西Ms8.1地震前区域构造变形背景[J].中国科学(D辑),2000,33(增刊):163-172.(Jiang Zaisen,et al.Horizntal strain field and tectonic de-formation of China mainland revealed by preliminary GPS result[J].Chinese Journal of Geophysics,2003,46(3):352-358)
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