Rescuers clear debris at Durbar Square after an earthquake with a 7.8 preliminary magnitude shook Kathmandu -- Nepal's capital -- and the densely populated Kathmandu Valley on Saturday, April 25, 2015. (Niranjan Shrestha/AP)

Photos: Earthquake strikes Nepal

An earthquake with a 7.8 preliminary magnitude struck Nepal on Saturday, April 25, 2015, resulting in mass casualties.