The rupture process of the Wenchuan earthquake demonstrated a transition from thrust-dominated slip to northeastward strike-slip motion along the Longmen Shan Fault Zone. The initial stress has been reported as playing a critical role in this process; however, the stress changes, especially those caused by the significant first subevent of the Wenchuan earthquake are not well understood. Here, we employ a three-dimensional finite element model of the Sichuan-Yunnan region to analyze the stress change caused by the significant first subevent and explore the possible influence on the following ruptures. The results indicate that the auxiliary maximum principal compressive stress (S_H) associated with the significant first subevent was horizontal and that the auxiliary stress regime was S_H>S_h>S_v, supporting the ongoing regional thrust motion near the southwestern segment of the rupture plane. However, in the northeastern segment, the auxiliary stress regime transitioned to S_H>S_v>S_h, demonstrating that the stress changes promoted the transition of the rupture behavior from predominantly thrust motion in the southwest to right-lateral strike-slip motion in the northeastern segment, which was also supported by the dominant shear stress change and the subtle normal stress change along the fault plane in the northeastern segment. In addition, our modeled results also indicate that the orientation of the maximum principal compressive stress changed from SEE to northeastward NEE along the strike of Longmen Shan Fault Zone. This anticlockwise rotation hastened the rupture behavior transition, suggesting that both the initial stress and the stress changes associated with the first subevent jointly controlled the following northeastward rupture of the Mw7.9 Wenchuan earthquake.

汶川地震的破裂过程展示了沿龙门山断裂带从逆冲为主的滑移向东北走滑运动的转变。据报道，初始压力在这个过程中起着关键作用。然而，应力变化，特别是由汶川地震第一次重大子事件引起的应力变化尚不清楚。在此，我们采用川滇地区三维有限元模型分析了重大第一次事件引起的应力变化，探讨了对后续破裂可能产生的影响。结果表明，与重要的第一子事件相关的辅助最大主压应力（S _H）是水平的，辅助应力状态为 S _H>S _h >S _v，支持破裂面西南段附近正在进行的区域推力运动。然而，在东北段，辅助应力状态转变为 S _H >S _v >S _h，表明应力变化促进了断裂行为从西南段以逆冲运动为主向东北段右旋走滑运动的转变，同时也得到了显性剪应力变化和沿线细微正应力变化的支持。东北段的断层面。此外，我们的模拟结果还表明，最大主压应力的方向沿龙门山断裂带的走向从 SEE 向东北向 NEE 变化。这种逆时针旋转加速了破裂行为的转变，表明初始应力和与第一次事件相关的应力变化共同控制了随后 Mw7.9 汶川地震的东北破裂。