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芦山地震前龙门山断裂带闭锁程度 与变形动态特征研究
引用本文:赵静,武艳强,江在森,牛安福,刘杰,王丽凤,魏文薪.芦山地震前龙门山断裂带闭锁程度 与变形动态特征研究[J].地震学报,2013,35(5):681-691.
作者姓名:赵静  武艳强  江在森  牛安福  刘杰  王丽凤  魏文薪
作者单位:1.中国北京 100045 中国地震台网中心
基金项目:国家“十二五”科技支撑计划课题(2012BAK19B02-02,2012BAK19B01-06);中国地震台网中心青年科技基金(QNJJPZ-YBB-1309)共同资助
摘    要:利用1999-2007和2009-2011年中国大陆GPS水平速度场数据, 采用DEFNODE(反演计算弹性岩石圈块体旋转、 应变和块体边界断层闭锁或同震滑动的Fortran程序)负位错反演程序估算了芦山地震前龙门山断裂带的三维闭锁程度, 并结合剖面结果分析了断层深浅部变形特征. GPS反演结果表明, 1999-2007年, 龙门山断裂中北段(闭锁比例为0.99)处于强闭锁(本文将闭锁比例大于0.97的称为强闭锁)状态; 龙门山断裂南段地表以下深度16 km内为强闭锁, 深度16-21 km处闭锁比例降低为0.62, 深度21-24 km处整条断裂逐渐转变为蠕滑状态. 2009-2011年, 即汶川地震后, 龙门山断裂中北段处于震后蠕滑状态; 龙门山断裂南段深度16-21 km处闭锁比例降低为0.45, 其它位置闭锁程度保持不变. GPS剖面结果显示, 2009-2011年, 即汶川地震后, 龙门山断裂中北段为逆冲兼右旋走滑运动; 而南段断层不能自由滑动、 变形宽度较大. 综合分析认为, 汶川地震时, 龙门山断裂南段并没有发生破裂, 一直处于较强的闭锁状态, 汶川地震的发生又加速了芦山地震的孕育进程; 由于龙门山断裂带南段的闭锁深度较中北段浅, 因此芦山地震较汶川地震强度低、 震级小、 破裂范围窄. 

关 键 词:芦山地震    DEFNODE负位错反演    断层闭锁比例    滑动亏空    变形特征
收稿时间:2013-05-13

Fault locking and dynamic deformation of the Longmenshan fault zone before the 2013 Lushan MS7.0 earthquake
Zhao Jing;Wu Yanqiang;Jiang Zaisen;Niu Anfu;Liu Jie;Wang Lifeng;Wei Wenxin.Fault locking and dynamic deformation of the Longmenshan fault zone before the 2013 Lushan MS7.0 earthquake[J].Acta Seismologica Sinica,2013,35(5):681-691.
Authors:Zhao Jing;Wu Yanqiang;Jiang Zaisen;Niu Anfu;Liu Jie;Wang Lifeng;Wei Wenxin
Institution:1.China Earthquake Networks Center, Beijing 100045, China2.Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China
Abstract:By using the negative dislocation model of DEFNODE, a Fortran program to model elastic lithospheric block rotations and strains, and locking or coseismic slip on block-bounding faults, we inverted the GPS horizontal velocity observations during 1999-2007 and 2009-2011 for a 3-D fault locking model of the Longmenshan fault zone before the Lushan earthquake, and analyzed characteristics of fault deformation at different depth in combination with GPS profiles. The inversion results indicate that during 1999-2007 the middle-northern segment of the Longmenshan fault was tightly locked (locked fraction is 0.99). Meanwhile the southern segment of the Longmenshan fault was tightly locked from the surface to the depth of 16 km, and the locked fraction decreases to about 0.62 at the depth of 16-21 km. The whole fault turns to creeping gradually between the depth of 21 km and 24 km. During 2009-2011, i.e., after the Wenchuan earthquake, the middle-northern segment of the Longmenshan fault was in a creeping state. Meanwhile the locked fraction of the southern segment of the Longmenshan fault decreased to about 0.45 at the depth of 16-21 km, and remained unchanged at other depths. In addition, the GPS profiles of 2009-2011 show that the middle-northern segment of the fault was thrust and dextral slip after the Wenchuan earthquake. The southern segment could not slip freely and the deformation width was large. Comprehensive analysis indicates that the southern segment of the Longmenshan fault has no rupture after the Wenchuan earthquake and is still tightly locked, and the Wenchuan earthquake speeds up the preparation process of the Lushan earthquake. Because the locked depth of the southern segment is lower than that of the middle-northern segment, therefore intensity, earthquake magnitude and rupture range of the Lushan earthquake are all less than those of the Wenchuan earthquake. 
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