The May 2015 M7.3 Earthquake in Nepal: Geological Setting and Event Details

The Himalayan region of Nepal lies at the active collisional boundary between the Indian and Eurasian tectonic plates. Convergence at rates of approximately 40–50 mm per year drives crustal shortening and uplift, producing the world’s highest mountain range. Strain accumulates along a series of north-dipping thrust faults, principally the Main Himalayan Thrust (MHT), which accommodates most of the plate motion at depths of 10–20 km. On 12 May 2015 at 07:05 UTC, an M7.3 earthquake struck central Nepal at a focal depth of 15 km. The event occurred 0 km from the reported epicenter and is recorded as the sole strong (M ≥ 7) earthquake in Nepal since 1 January 2000. Its shallow depth and thrust mechanism are consistent with rupture along the MHT, the same fault system responsible for the region’s long-term seismic hazard. The 2015 sequence released part of the elastic strain built up over decades of plate convergence. Aftershocks and geodetic measurements indicate that slip propagated eastward from the earlier April mainshock, further loading adjacent fault segments. Nepal’s historical record shows that great earthquakes (M ≥ 8) have repeatedly ruptured the MHT at intervals of several centuries, underscoring the persistent seismic risk in the region. Surface effects included widespread landsliding in steep terrain and liquefaction in river valleys. The earthquake’s proximity to the capital and densely populated valleys amplified societal impacts, yet the geological processes that generated it remain fundamental expressions of ongoing Himalayan orogenesis.

References

USGS Earthquake Catalog (event parameters)
USGS Earthquake Hazards Program (tectonic setting summaries)