Stress change from the 2015 Mw 7.8 Gorkha earthquake and increased hazard in the southern Tibetan Plateau

Abstract

We examine the co-seismic Coulomb stress change induced by the 2015 Mw 7.8 Gorkha, Nepal earthquake and investigate its influence on the seismic hazard in the southern Tibetan Plateau. We find that the location of the aftershocks coincides with areas where stress was enhanced. This stress enhanced area also covers the west and the shallow fault section updip of the 2015 Gorkha earthquake rupture in the Main Himalayan Thrust fault (MHT), signaling the raising hazard of the seismic gaps in the west and south to Kathmandu. The 2015 Gorkha earthquake strongly interacted particularly with the normal and thrust faults in the distance of around 100–250km from the rupture zone by bringing stress closer to the Coulomb failure. This fault interaction process increased stress by 12kPa and 100kPa at the southern end of the Tingkye and the Nyalam normal faults, respectively, triggering the Ms 5.9 Tingri earhquake on 25 May 2015 and the Ms 5.3 Nyalam earthquake on 26 May 2015. Stress in the Main Frontal Himalaya Thrust fault (MFT), the Main Boundary Thrust fault (MBT) in the Lalitpur area of Nepal was promoted by 40–100kPa. Such stress transfer should facilitate the future rupture on these active faults and raise seismic hazard in the southern Tibetan Plateau.