The Shaanxi earthquake or Hua County earthquake of 1556 is the deadliest earthquake on record, killing approximately 830,000 people. It occurred on the morning of 23 January 1556 in Shaanxi, China. More than 97 counties in the provinces of Shaanxi, Shanxi, Henan, Gansu, Hebei, Shandong, Hubei, Hunan, Jiangsu and Anhui were affected.http://www.kepu.ac.cn/english/quake/ruins/rns03.html A 520 mile-wide area was destroyed and in some counties, sixty percent of the population was killed.http://www.drgeorgepc.com/EarthquakesChina.html Most of the population in the area at the time lived in artificial caves in loess cliffs, many of which collapsed during the disaster.