The 12 May 2015 Kodari Earthquake (M_w 7.3) in Central Nepal:Delayed Triggering by the 25 April 2015 Gorkha Earthquake (M_w 7.8)

Abstract

The 12 May 2015 earthquake of M w 7.3 occurred in the Kodari region, Central Nepal, 17 days after the 25 April 2015 Gorkha earthquake (M w 7.8) along the Himalayan plate boundary. Both the earthquakes were associated with predominantly thrust faulting on the Main Himalayan Thrust (MHT). This is the largest aftershock of the 2015 Gorkha earthquake which occurred approximately 150 km east of it. Our analysis suggests that the 2015 Gorkha earthquake significantly increased the Coulomb stress on the shallow unruptured and updip part of the MHT, further west of the 2015 rupture and also in the hypocentre region of 12 May 2015 M w 7.3 aftershock. In the following 17 days period, Coulomb failure stress increased further by the relaxation of coseismic pore pressure on the eastern side of its coseismic rupture, where the 12 May 2015 aftershock had occurred.