1976 Tangshan Earthquake

At 3:42 a.m. on 28 July 1976, a 7.6-magnitude earthquake struck the industrial city of Tangshan in Hebei Province, China, while nearly 1 million residents slept. The city was almost entirely levelled within 23 seconds; official figures cited 242,000 deaths, though some estimates place the toll at over 650,000. A major aftershock of 7.1 struck 16 hours later. The disaster struck during China's Cultural Revolution, and the government initially refused foreign aid, hampering the rescue effort. Its magnitude was 0.5 lower than the 2004 Indian Ocean Tsunami, yet it caused a higher toll than any earthquake in the 20th century.