东昆仑断裂粘滑错动对青藏铁路变形效应的数值模拟
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摘要
东昆仑断裂是青藏高原北部现今仍在强烈活动的地震断裂之一, 该断裂的未来地震活动及其突发性粘滑错动是青藏铁路面临的重大工程地质问题。基于东昆仑断裂的运动学特征, 通过分别加入8m和3m的水平左旋位移, 模拟了东昆仑断裂未来地震活动时震中位于铁路线附近和远离铁路2种情形下的铁路变形效应。模拟结果表明: 震中位于铁路线附近时, 断裂南侧基岩和第四系均发生8m的左旋走滑位移, 而铁路附近的第四系水平位移明显减小, 铁轨和道床没有明显的断错, 表现为4~5m的连续左旋弯曲变形; 铁路东、西两侧形成NE向的张裂陷和NW向的地震鼓包,而道床和铁轨的垂直位移幅度较小。震中远离铁路时的变形效应与震中位于铁路线附近时的变形相似, 但位移幅度减小, 铁轨和道床形成1~2m的连续左旋弯曲变形。因此, 东昆仑断裂未来再次发生7~8级强烈地震时, 无论地震震中远离铁路还是在铁路附近, 其断裂的突发性粘滑错动都将导致青藏铁路的大变形和破坏。
The Eastern Kunlun Fault (EKF) is one of the most active seismogenic faults in the northern Qinghai Tibet Plateau. Earthquake activities in the future or abrupt strike slip movement of the EKF will bring serious hazards to Qinghai Lhasa railway. On the basis of kinematics character of the EKF, this paper stimulates two deformation effects (the epicenter is located near the railway or far away it) when the earthquakes with 8 m and 3 m level left lateral displacement, occur respectively. The result shows that the southern bedrock and Quaternary of the EKF have 8 m left lateral strike slip displacement when epicenter is located near the railway. However, the level displacement of Quaternary near the railway is smaller, rail and groundsill show successive left lateral crooked deformation. It has just 4-5 m successive left lateral crooked deformation; Two sides of the railway cause the N E direction tensile opening and N W direction earthquake apophysis. Deformation effect is similar when the epicenter is located far away the railway, but the extent of displacement became smaller, and the rail and groundsill have the 1-2 m successive left lateral crooked deformation. Therefore, the great earthquake induced by EKF in the future will result in great deformation and destruction of Qinghai Lhasa railway whether the epicenter is located near the railway or not
The Eastern Kunlun Fault (EKF) is one of the most active seismogenic faults in the northern Qinghai Tibet Plateau. Earthquake activities in the future or abrupt strike slip movement of the EKF will bring serious hazards to Qinghai Lhasa railway. On the basis of kinematics character of the EKF, this paper stimulates two deformation effects (the epicenter is located near the railway or far away it) when the earthquakes with 8 m and 3 m level left lateral displacement, occur respectively. The result shows that the southern bedrock and Quaternary of the EKF have 8 m left lateral strike slip displacement when epicenter is located near the railway. However, the level displacement of Quaternary near the railway is smaller, rail and groundsill show successive left lateral crooked deformation. It has just 4-5 m successive left lateral crooked deformation; Two sides of the railway cause the N E direction tensile opening and N W direction earthquake apophysis. Deformation effect is similar when the epicenter is located far away the railway, but the extent of displacement became smaller, and the rail and groundsill have the 1-2 m successive left lateral crooked deformation. Therefore, the great earthquake induced by EKF in the future will result in great deformation and destruction of Qinghai Lhasa railway whether the epicenter is located near the railway or not
引文
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[3] 王治华青藏公路及铁路沿线的活动构造与其次生灾害[J]现代地质,2003,17(3):227-236
[4] 王治华青藏公路和铁路沿线的滑坡研究[J]现代地质,2003,17(4):355-362
[5] VanDerWoerdJ,RyersonFJ,TapponnierP, etalUniformslip ratealongtheKunlunfault: implicationsforseismicbehav iourandlarge scaletectonics[J]GeophysicalResearchLetters,2000,27(16):2353-2356
[6] VanDerWoerdJ,RyersonFJ,TapponnierP,etalHoloceneleftslip ratedeterminedbycosmogenicsurfacedatingontheXidatansegmentoftheKunlunfault(Qinghai,China)[J]Geology,1998,26(8):695-698
[7] 中国地震局中国昆仑山口西81级地震图集[M]北京:地震出版社,2003
[8] 陈杰,陈宇坤,丁国瑜,等2001年昆仑山口西Ms81地震地表同震位移分布特征[J]地震地质,2004,26(3):378-392
[9] 崔之久,伍永秋,刘耕年,等昆仑山垭口地区晚新生代以来的气候构造事件[A]青藏项目专家委员会青藏高原形成演化、环境变迁与生态系统研究[C]北京:科学出版社,1996
[10] 吴中海,胡道功,吴珍汉青藏铁路邻侧昆仑山2001年Ms81级地震地表破裂特征分析[J]地球学报,2004,25(4):411-414
[11] 赵瑞斌,李军,向志勇,等昆仑山口西81级地震地表破裂带西段考察[J]内陆地震,2002,16(2):175-179
[12] 吴树仁,李贵书,何锋,等昆仑山地震地表破裂带东段几何学与运动学[J]地质通报,2002,21(8-9):554-561
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