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汶川地震发生于巴颜喀拉、华南和川滇菱形块体“三联点”附近,对周边块体和川滇地区主要断裂带也即块体边界带的影响不容忽视.本文基于最新得到的1999~2007、2009~2011和2011~2013年GPS复测结果,利用二维有限元接触模型和“块体加载”方法,模拟强震前后断裂带的运动与受力变化.结果显示汶川地震前龙门山断裂带为低速运动但挤压应力快速积累,汶川地震后巴颜喀拉、滇西南、菱形块体向E-SSE逃逸增强,龙门山断裂带右旋、挤压运动速率和压应力年积累量最高值分别为震前的4.5、2.1和2.5倍.鲜水河南段、安宁河、则木河、大凉山和丽江-小金河断裂带挤压应力快速积累,并形成横跨川滇中部沿NE向展布的挤压应力增强带.鲜水河断裂带中部拉张增强并出现短暂反向.上述变化与该区同期中强地震分布关系密切,揭示出地震活动空间迁移与块体运动变化有关.
The Wenchuan earthquake occurred in the vicinity of the “triple point” of the Bayanhar, South China and Sichuan-Yunnan rhombic blocks, and can not ignore the influence of the surrounding blocks and the main fault zone, ie, the block boundary zone in Sichuan-Yunnan region. Based on the latest findings The results of GPS reanalysis from 1999 to 2007, 2009 ~ 2011 and 2011 ~ 2013 were used to simulate the movement and stress changes of the fracture zone before and after strong earthquakes by using the two-dimensional finite element contact model and the “bulk loading” method. Longmenshan fault zone before Wenchuan earthquake was low-velocity movement but compressive stress was rapidly accumulated. After Wenchuan earthquake, the escape of E-SSE to the diamond block in Bayan Har, southwestern Yunnan increased, and the right-lateral and extrusional velocity of the Longmenshan fault zone and The maximum annual compressive stress is 4.5, 2.1 and 2.5 times that before the earthquake, respectively.The compressive stress of the Xinyu River, Anning River, Zemuhe, Daliangshan and Lijiang-Xiaojinhe fault zones accumulate rapidly and form a The compressive stress zone is distributed along the NE direction in the central Sichuan-Yunnan region, and the central stretch of the Xianshuihe fault zone is enhanced and appears in a short reverse direction.These changes are closely related to the distribution of moderate-strong earthquakes in the same period of the region, revealing the spatial distribution of seismic activity Block movement related changes.