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采用有限元方法模拟了印度板块的持续向北推进、挤压对龙门山断裂带及其邻区的影响,根据模拟结果 ,对比GPS、地震和地质学观测数据,定量分析了汶川大地震发生前断裂带的走滑速率以及最大主应力的分布特征,据此探讨了汶川大地震的发震机理.模型由弹性上地壳和粘弹性下地壳组成,其中上地壳包括了青藏高原、四川盆地、华南地块以及印支地块,块体内断层的处理方法主要采用了库仑摩擦模型.研究结果如下:(1)通过调整龙门山断裂带摩擦系数,发现伴随摩擦系数值的增加断裂带走滑速率逐渐降低,当其达到0.95,已接近GPS测量结果 .由此可认为龙门山断裂带应处于强摩擦环境.(2)与松潘甘孜地块中其它区域相比,整个龙门山地区处于高摩擦强度、低应力的环境下,这有利于能量缓慢而稳定的积累直至达到其破裂极限,从而引发强烈地震.(3)沿龙门山断裂带上下两盘的最大主应力分布特征具有很强的规律性,自西南到东北可划分出泸定-大邑、大邑茂县、茂县北川、北川青川四段.其中上、下两盘应力差最大值出现在大邑茂县段14～20 km处,应力差最小值出现在泸定大邑段,而北川茂县段上、下两盘的应力值则十分接近.这种最大主应力的分布特征与汶川地震余震震中的空间分布特征十分相似.
The finite element method is used to simulate the influence of the Indian plate thrusting northward and squeezing on the Longmenshan fault zone and its adjacent area. According to the simulation results, the GPS, seismic and geological observation data are compared to quantitatively analyze the Wenchuan earthquake The strike-slip mechanism of the Wenchuan earthquake is discussed.The model consists of elastic upper crust and viscoelastic lower crust, in which the upper crust includes the Qinghai-Tibet Plateau, the Sichuan Basin, the South China (1) By adjusting the friction coefficient of the Longmenshan fault zone, it is found that the slip rate of the fault zone gradually increases with the increase of the friction coefficient, as well as the Coulomb friction model Decreases, and when it reaches 0.95, it is close to the result of GPS measurement. Therefore, the Longmen Shan fault zone should be considered as a strong friction environment. (2) Compared with other areas in the Songpan-Garzê block, the Longmenshan area is in high frictional strength, In a low-stress environment, this favors a slow and steady accumulation of energy until its rupture limit is reached, resulting in strong earthquakes. (3) Up and down along the Longmenshan fault zone The maximum principal stress distribution characteristics of the plate has a strong regularity, from the southwest to northeast can be divided into Luding - Dayi, Dayi Maoxian, Maoxian Beichuan, Beichuan Qingchuan four sections of which the upper and lower stress difference maximum appears At 14-20 km in Dayi County of Dayi, the minimum stress difference appears in Dayi section of Luding, while the stress values of the two upper and lower sections in Beichan section are close to the same. The distribution of the maximum principal stress is similar to that of the Wenchuan earthquake The aftershock epicenter spatial distribution characteristics are very similar.