On 25 April 2015, a devastating earthquake of moment magnitude of 7.8Mw killed nearly 9,000 people and injured nearly 22,000. It was the worst natural disaster to strike the country since the 1934 Nepal–Bihar earthquake. The earthquake also triggered an avalanche on Mount Everest, killing 21. Centuries-old buildings including the UNESCO World Heritage Sites in the Kathmandu valley were destroyed. A major aftershock occurred on 12 May 2015 at 12:50 NST with a moment magnitude (Mw) of 7.3, killing more than 200 people and over 2,500 were injured by this aftershock, and many were left homeless. These events led to a major humanitarian crisis which affected the reconstruction after the earthquake.