汶川地震后龙门山断裂带活动特征

Active faulting along the Longmenshan fault zone after the 8.0 magnitude Wenchuan earthquake in Sichuan

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 Siehuan. The measurements of the velocity fields with GPS show that compared with the regimes of movements before the Wenehuan 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.