【摘要】 利用GPS等观测资料研究了2008年汶川8.0级地震前的区域地壳运动与构造变形、应变积累,以及大区域地壳运动微动态变化过程,结合同震位移场分布等分析、讨论了汶川地震前近10年区域地壳变形的表象所反映的大震孕震最后阶段的物理过程.结果表明,发生汶川8.0级地震的龙门山断裂带1999-2004年相对稳定的华南地块无明显的相对运动,2004-2007年有一定程度的相对运动显示,以右旋活动为主,年速率为1. 6mm/a.龙门山断裂带西北侧的巴颜喀拉地块东部为右旋剪切为主兼有推挤的大尺度缓慢变形状态,右旋扭动变形率为2.1±0.2(10^-8/a),地壳总体缩短变形率为-0.7±0.1(10^-8/a).由GPS基准站资料计算的基线时间序列显示,2005年以来大尺度北东向地壳缩短的相对运动明显增强,青藏块体相对华南地块的北东向运动明显增强.对汶川大地震前应变积累的特殊性等问题进行了初步讨论,分析认为,汶川大地震的发生是四川盆地西缘的龙门山断裂带受到其西侧巴颜喀拉地块推挤导致大尺度、长时期、缓慢的地壳应变积累的结果.在发震前不仅龙门山断裂带为显著闭锁状态,且孕震区域可能存在地壳弹性变形趋于极限后难以发生变形的相持阶段,大尺度地壳运动与动力环境的动态变化对汶川大地震的发生有促进影响.更多还原

【Abstract】 In this paper, the physical process of earthquake pregnant in the 10 years before Wenchuan 8. 0 earthquake occurring in 2008 which reflected by regional crustal deformation is discussed, which includes the analysis of regional tectonic deformation, strain accumulation, the micro-dynamic process of crustal movement on large scale and co-seismic displacement fields. The Wenchuan 8. 0 earthquake locates at the middle piece of Longman Mountain, which the horizontal relative movement is not obvious relative to steady South China block in the period of 1999- 2004. From 2004 to 2007, small horizontal different movement （1. 6 mm/a）, especially dextral movement, shows in the middle piece of Longman Mountain. The east Bayan Har block locating at the northwest of Longman Mountain faults shows dextral shearing deformation and slowly pushing and squeezing deformation on large scale, which dextral deformation is about 2. 1+0. 2 (l0^-8/a) and crustal shortening deformation is about 2. 1 + 0. 2(10^-8/a). Based on the GPS geodesic time series, the relative compression movement in northeast direction on large scale enhances obviously from 2005, and the northeast direction movement of Qinghai-Tibet block relative to South China block enhance obviously too. Under the discussion to the special characteristic of strain accumulation before Wenchuan earthquake, we consider that the . occurrence of this earthquake is the result of slowly crustal strain accumulation on large scale and in long period, which caused by the pushing and squeezing effect of Bayan Har block. Before earthquake. Longmen Mountain faults are in the locking status, and the earthquake pregnant area is in the deadlock stage which can not bring deformation caused by the elastic deformation limit. On the other hand, the crustal movement on large scale and the tectonic dynamic changing are beneficial to occurrence of Wenchuan earthquake.更多还原