According to the Encyclop?dia Britannica, the Shaanxi earthquake occurred due to movement along the three major fault lines that form the basin of the Wei River. Considered to be the most deadly earthquake in history, the 1556 earthquake left approximately 830,000 people dead and altered the landscape of the Shaanxi province.
The Shaanxi earthquake is estimated to have been a magnitude 8 earthquake. Although the actual earthquake lasted for only a few seconds, it killed up to 60 percent of the population in two provinces, changed the paths of rivers, created massive floods and set off fires that burned for several days.
The earthquake struck late at night on Jan. 23, and had several aftershocks that continued the following morning, according to History.com. While it is not the strongest earthquake ever recorded, it struck in a highly populated area made up predominately of poorly constructed homes and buildings. This resulted in the high number of casualties, as all the structures in many of the cities near the epicenter ? the Wei River Valley ? were destroyed. In some areas, a 60-foot deep crevice opened in the ground. Serious landslides were associated with the earthquake, and severe destruction spanned up to 300 miles from the epicenter.