Fault Interaction and Earthquake Triggering during Coseismic Process of Wenchuan Earthquake

The 2008 MS 8.0 Wenchuan earthquake occured in Wenchuan, Sichuan province caused many casualties and huge economical losses. The northern part of Longmen Shan piedmont fault moved after the main event, with a burst to the surface. Using a model of two faults (Yingxiu-Beichuan and Guanxian-Jiangyou fault), we discussed the earthquake triggering mechanism and time delay of the fault frictional instability of Longmenshan piedmont fault. Based on the rate- and state- dependent frictional law, we deduced time delay of new rupture on either condition that shear stress rate is zero or not, and used the results to infer the coseismic process of Wenchuan earthquake. After comparing the time delay of friction instability of Longmenshan piedmont fault, which was derived from three components of strong ground motion observational data of Mianzhu-Qingping and Wenchuan-Wolong stations, we obtained the same results. We found that Yingxiu-Beichuan and Guanxian-Jiangyou fault did not move together at the same time, but the dynamic seismic waves (stress waves) radiated from Yingxiu-Beichuan fault triggered the movement of Guanxian-Jiangyou fault, with a possible time delay of several seconds.