Stress changes on major faults caused by 2013 Lushan earthquake and its relationship with 2008 Wenchuan earthquake

On April 20, 2013, an M (s)7.0 earthquake occurred in Ya'an-Lushan region, Sichuan Province, China, killing and injuring more than one thousand people. Therefore, it is critical to outline the areas with potential aftershocks before reconstruction and re-settlement as to avoid future disasters. Based on the elastic dislocation theory and multi-layered lithospheric model, we calculate the co- and post-seismic stress changes caused by the Wenchuan and Lushan earthquakes to discuss the relationship between M (w)7.9 Wenchuan earthquake and M (s)7.0 Lushan earthquake, the influences on the distribution of aftershock caused by the Lushan earthquake, and the stress changes on major faults in this region. It is shown that the Coulomb failure stress increment on the hypocenter of Lushan earthquake caused by the Wenchuan earthquake is about 0.0037-0.0113 MPa. And the possible maximum value (0.0113 MPa) is larger than the threshold of stress triggering. Therefore, the occurrence of Lushan earthquake is probably effectively promoted by the Wenchuan earthquake. The aftershock distribution is well explained by the co-seismic stress changes of Lushan earthquake. By the two ends of the rupture of Lushan earthquake with increased Coulomb failure stress, a lack of aftershock recordings indicates the high seismic hazard. The stress accumulation and corresponding seismic hazard on the Kangding-Dafu segment of the Xinshuihe fault, the Beichuan-Yingxiu fault, the Pengxian-Guanxian fault, and the Ya'an fault are further increased by the Lushan earthquake and post-seismic process of Wenchuan earthquake.