The aftershock sequence of the 2015 April 25 Gorkha–Nepal earthquake

Abstract

The M 7.8 2015 April 25 Gorkha earthquake devastated the mountainous southern rim of the High Himalayan range in central Nepal. The main shock was followed by 553 earthquakes of local magnitude greater than 4.0 within the first 45 days. In this study, we present and qualify the bulletin of the permanent National Seismological Centre network to determine the spatio-temporal distribution of the aftershocks. The Gorkha sequence defines a 140-km-long ESE trending structure, parallel to the mountain range, abutting on the presumed extension of the rupture plane of the 1934 M 8.4 earthquake. In addition, we observe a second seismicity belt located southward, under the Kathmandu basin and in the northern part of the Mahabarat range. Many aftershocks of the Gorkha earthquake sequence have been felt by the 3 millions inhabitants of the Kathmandu valley.