Regional and Teleseismic Source Inversion of the M7.8 Nepal Earthquake Sequence

Abstract:

On April 25, 2015 a large M7.8 earthquake stroke Nepal and devastated the region. The Gorkha earthquake, as well as its following aftershock sequence, was quickly monitored by the French National Data Center (NDC), which has for mission to monitor seismic activity around the world, and to report on the occurrence of significant seismic events. In addition to the phase picking and localization of the events, seismic source studies are performed at the French NDC. Two approaches using regional and teleseismic data are traditionally considered depending on the magnitude of the events and the distance range between epicenters and stations. In the case of the Nepalese sequence we present source inversion results using several methods for the larger events of the sequence. The source solutions obtained at long periods agree together, and indicate shallow dipping thrust mechanisms on the main Himalayan thrust fault. They also provide information on the coseismic displacements associated with the events. Finally, in-depth source sensitivity studies from waveform inversion and pP/sP phases help constrain the depth of the events.