汶川地震后龙门山断裂带活动特征
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摘要
利用地震后2009～2011年GPS监测数据,获得了龙门山断裂带所在地区2009～2010年、2010～2011年以及2009～2011年GPS测站运动速度场,分析了区域地壳运动总体趋势及形变特征;通过分析龙门山断裂带北段、中段、南段横切剖面的测站运动速度变化,探讨了汶川地震后龙门山断裂带运动特征。分析表明:汶川地震前后,地壳运动总体趋势未变,作顺时旋转;断裂带西侧GPS测站运动速度变大,东侧运动速度变小;龙门山断裂带的断裂性质地震前后都为右旋走滑挤压,断裂带运动速率受汶川地震影响较大,震后运动速率较震前有显著的增加。龙门山断裂带震后各段次级断裂活动不同,中南段以前山断裂运动为主,其它各段以后山断裂运动为主。地震后龙门山断裂带表现出的运动特征主要与地震活动有关。受汶川地震的影响,区域动力学、运动学平衡被打破,龙门山断裂带东侧震后初期弹性回返,表现为低速反向运动。龙门山断裂带西侧震后松弛为拉张区,运动速度加大。地震对断裂带的影响不同,导致断裂带各段及次级断裂表现出不同的运动特征。
The overall trend and deformation of the regional crustal movements are examined on the basis of the velocity fields from the GPS monitoring stations along the Longmenshan fault zone in the years of 2009-2010,2010-2011 and 2009-2011,respectively in combination with 2009-2011 GPS measurements after the 8.0 magnitude Wenchuan earthquake in Sichuan.The measurements of the velocity fields with GPS show that compared with the regimes of movements before the Wenchuan earthquake,no distinctive differences are observed after that about the overall trend of the regional crustal movements;the regional crustal movements still display the patterns of clockwise rotation and dextral strike slip and compression.However,the velocities of movements are noticeably increasing.The regional equillibium of dynamics and kinematics has been destructed because of the influence of the Wenchuan earthquake.The low-velocity reverse movements occurred on the eastern side of the Longmenshan fault zone due to elastic inversion at the onset of the earthquake,while the western side of it has been in the extensional area with higher velocities of movements.The crustal movement and deformation are progressively reconstructed to the regional states before the earthquake in response to the stress-strain release in the study area.
The overall trend and deformation of the regional crustal movements are examined on the basis of the velocity fields from the GPS monitoring stations along the Longmenshan fault zone in the years of 2009-2010,2010-2011 and 2009-2011,respectively in combination with 2009-2011 GPS measurements after the 8.0 magnitude Wenchuan earthquake in Sichuan.The measurements of the velocity fields with GPS show that compared with the regimes of movements before the Wenchuan earthquake,no distinctive differences are observed after that about the overall trend of the regional crustal movements;the regional crustal movements still display the patterns of clockwise rotation and dextral strike slip and compression.However,the velocities of movements are noticeably increasing.The regional equillibium of dynamics and kinematics has been destructed because of the influence of the Wenchuan earthquake.The low-velocity reverse movements occurred on the eastern side of the Longmenshan fault zone due to elastic inversion at the onset of the earthquake,while the western side of it has been in the extensional area with higher velocities of movements.The crustal movement and deformation are progressively reconstructed to the regional states before the earthquake in response to the stress-strain release in the study area.
引文
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[2]张培震,王琪,马宗晋.中国大陆现今构造变形的GPS速度场与活动地块[J].地学前缘,2002,9(2):430-441.
[3]林茂炳,苟宗海.四川龙门山造山带造动带造山模式研究[M].成都:成都科技大学出版社,1996.
[4]邓起东,陈社发,赵小麟.龙门山及其邻区的构造和地震活动及动力学[J].地震地质,1994,16(4):389-403.
[5]唐文清,孙志明.四川松潘弓嘎岭-漳腊盆地新构造运动[J].特提斯地质,1999,23:103-107.
[6]赵小麟,邓起东,陈社发,等.龙门山逆断裂带中段的构造地貌学研究[J].地震地质,1994,16(4):422-428.
[7]陈社发,邓起东,赵小麟.龙门山中段推覆构造带及相关构造的演化历史和变形机制(一)[J].地震地质,1994,16(4):404-412.
[8]许志琴,侯立玮,王宗秀.中国松潘一甘孜造山带的造山过程[M].北京:地质出版社,1992.
[9]BURCHFIEL B C,CHEN Z L,LIU Y P et al.Tectonics of theLongmenshan and adjacent regions[J].International GeologicalReview,1995,8:661-735.
[10]CHEN SHEFA,WILSON C J L et al.Active faulting andmovement associated with large earthquakes in the Min Shan andLongmen Mountains,northeastern Tibetan Plateau[J].Journal ofGeophysical Research.1994,9(12):24,025-24,038.
[11]张培震.青藏高原东缘川西地区的现今构造变形、应变分配与深部动力过程.中国科学(D辑)[J],2008,38(9):1-15.
[12]唐荣昌,韩渭宾主编.四川活动断裂与地震[M].北京:地震出版社,1993:67-138.
[13]张培震,闻学泽,徐锡伟,等.2008年汶川8.0级特大地震孕育和发生的多单元组合模式[J].2009,54(7):944-953.
[14]王琪,张培震,牛之俊,等.中国大陆现今地壳运动和构造变形[J].中国科学(D辑),2001,31(7):529-536.
[15]陈智梁,张选阳,沈凤,等.中国西南地区地壳运动的GPS监测[J].科学通报,1999,44(8):851-854.
[16]唐文清,刘宇平,陈智梁,等.龙门山断裂构造带GPS研究[J].大地测量与地球动力学,2004,24(3):57-60.
[17]唐文清,陈智梁,刘宇平,等.鲜水河、龙门山断裂交汇区现今构造GPS研究[J].地质通报,2005,24(12):1169-1172.
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