The Coulomb stress change caused by the 2013 Ms7.0 Lushan Earthquake

The Ms7.0 Lushan Earthquake on 20 April 2013,Sichuan Province,resulted from a north-south striking fault with reverse-type motion.This event occurred on the southern part of Longmenshan fault.The epicenter of the Ms7.0 Lushan Earthquake locates southwest 85 km from the Ms8.0 Wenchuan Earthquake on 12 May 2008.There is a seismic gap segment with 20 to 30 km long along the main rupture fault between two earthquake groups.In this study,we calculated the Coulomb stress change induced by the Ms8.0 Wenchuan Earthquake at first and then find that the Ms7.0 Lushan Earthquake was induced by the Ms8.0 Wenchuan Earthquake.Our analysis results show the Ms7.0 Lushan Earthquake epicenter is located in the increasing region of Coulomb stress after the Ms8.0 Wenchuan Earthquake.Then we calculate the Coulomb stress change caused by the Ms7.0 Lushan Earthquake and find that the influence of the Ms7.0 Lushan Earthquake on the gap segment results from the increasing of Coulomb stress.Furthermore we calculated the stress change of the region nearby induced by both the Wenchuan and the Lushan earthquakes.The Coulomb stress of the eastern border between Sichuan and Yunnan provinces has been increased as well.