The 25 April 2015, Mw7.8 Gorkha, Nepal, earthquake ruptured a shallow section of the Indian‐Eurasian plate boundary by reverse faulting with NNE‐SSW compression, consistent with the direction of current Indian‐Eurasian continental collision. The Gorkha main shock and aftershocks were recorded by permanent global and regional arrays and by a temporary local broadband array near the China‐Nepal border deployed prior to the Gorkha main shock. We relocate 272 earthquakes with Mw>3.5 by applying a multiscale double‐difference earthquake relocation technique to arrival times of direct and depth phases recorded globally and locally. We determine a well‐constrained depth of 18.5 km for the main shock hypocenter which places it on the Main Himalayan Thrust (MHT). Many of the aftershocks at shallower depths illuminate faulting structure in the hanging wall with dip angles that are steeper than the MHT. This system of thrust faults of the Lesser Himalaya may accommodate most of the elastic strain of the Himalayan orogeny.

The Himalaya orogenic belt produces frequent large earthquakes that affect population centers along a length of over 2500 km. The 2015 Gorkha, Nepal earthquake (Mw 7.8) ruptured the Main Himalayan Thrust (MHT) and allows direct measurements of the behavior of the continental collision zone. We study the MHT using seismic waveforms recorded by local stations that completely cover the aftershock zone. The MHT exhibits clear lateral variation along geologic strike, with the Lesser Himalayan ramp having moderate dip on the MHT beneath the mainshock area and a flatter and deeper MHT beneath the eastern end of the aftershock zone. East of the aftershock zone, seismic wave speed increases at MHT depths, perhaps due to subduction of an Indian basement ridge. A similar magnitude wave speed change occurs at the western end of the aftershock zone. These gross morphological structures of the MHT controlled the rupture length of the Gorkha earthquake.