Source characteristics of the 2015 M W 7.8 gorkha (Nepal) earthquake and its M W 7.2 aftershock from space geodesy

Abstract On April 25, 2015, a destructive M W 7.8 earthquake struck the capital of Nepal, Kathmandu, killing more than 8800 people and destroying numerous historical structures. We analyze six coseismic interferograms from several satellites (ALOS-2, Sentinel-1 A, and RADARSAT-2), as well as three-dimensional displacements at six GPS stations to investigate fault structure and slip distribution of the Gorkha earthquake. Using a layered crustal structure, the best-fit slip model shows that the preferred dip angle of the mainshock fault is 6 ± 3.5° and the major slip is concentrated within depths of 8–15 km. The maximum slip of ~ 6.0 m occurs at a depth of 11 km, 70 km south east of the epicenter. The coseismic rupture extends ~ 150 km eastward of the epicentre with a cumulative geodetic moment of 7.8 × 10 20  Nm, equivalent to an earthquake of M W 7.84. We also investigate the M W 7.2 aftershock on 12 May 2015 using another three postseismic interferograms from ALOS2, RADARSAT-2, and Sentinel-1 A. The InSAR-based best-fit slip model of the largest aftershock implies that its major slip is next to the eastern lower end of the mainshock rupture with a similar maximum slip of ~ 6 m at a depth of ~ 13 km. This study generates various coseismic geodetic measurements to determine the source parameters of the M W 7.8 Gorkha earthquake and 12 May M W 7.2 afershock, providing an additional chance to understand the local fault structure and slip extent.