Abstract: Using multi-layered viscoelastic media, we calculated the Coulomb failure stress changes on the faults surrounding the Longmenshan fault zone which caused by co-seismic and post-seismic effects of the May 12, 2008 Wenchuan 8.0 earthquake and the April 20，2013 Lushan 7.0 earthquake. The result shows that, both co-seismic effects and post-seismic effects of the Wenchuan 8.0 earthquake increased the Coulomb stress on the epicenter of the Lushan 7.0 earthquake, it benefitted the occurrence of the Lushan earthquake. The distribution of the Coulomb stress changes on the surrounding faults shows that, the two large earthquakes above mentioned caused significant increases of Coulomb stress on the segments between the two events. In addition, faults whose Coulomb stress increased significantly included the middle segment of Xianshuihe fault zone, the north segment of Guanxian- Anxian fault，the parts of Wenxian fault, the north segment of Pingwu-Qingchuan fault and Lueyang一 Mianxian fault. And faults whose Coulomb stress decreased significantly included the Maerkang fault, the southern end of Minjiang fault, Huya fault, the northern end of Longquanshan fault and the north segment of Beichuan-Yingxiu fault.

Key words: Coulomb failure stress changes, Interactions between faults, The 2008 Wen-chuan 8. 0 earthquake, The 2013 Lushan 7. 0 eart hquake, The Longmenshan fault zone