Shaanxi China January 23 1556

Last Updated on Mon, 06 Dec 2021 | Plate Tectonics

The deadliest earthquake and mass-wasting event on record occurred in 1556 in the central Chinese province of shaanxi. Most of the 830,000 deaths from this earthquake resulted from landslides and the collapse of homes built into loess, a deposit of wind-blown dust that covers much of central China. The loess represents the fine-grained soil eroded from the Gobi desert to the north and west and deposited by wind on the great loess plateau of central China. Thus, this disaster was triggered by an earthquake but mass-wasting processes were actually responsible for most of the casualties.

The earthquake that triggered this disaster on the morning of January 23, 1556, leveled a 520-mile-wide area and caused significant damage across 97 counties in the provinces of shaanxi, shanxi, Henan,

Hebei, hubei, shandong, Gansu, Jiangsu, and Anhui. sixty percent of the population was killed in some counties. There were no modern seismic instruments at the time, but seismologists estimate that the earthquake had a magnitude of 8 on the Richter scale, with an epicenter near Mount Hua in Hua County in shaanxi.

The reason for the unusually high death toll in this earthquake is that most people in the region at the time lived in homes carved out of the soft loess, or silty soil. People in the region would carve homes, called Yaodongs, out of the soft loess, benefit from the cool summer temperatures and moderate winter temperatures of the soil, and also have an escape from the sun and blowing dust that characterizes the loess plateau. The shaking from the magnitude 8 earthquake caused huge numbers of these Yaodongs to collapse, trapping the residents inside. Landslides raced down steep loess-covered slopes, and the long shaking caused the yaodongs even in flat areas to collapse.

Time tends to make people forget about risks associated with natural hazards. For events that occur only every couple of hundred years, several generations may pass between catastrophic events, and each generation remembers less about the risks than the previous generation. This character of human nature was unfortunately illustrated by another earthquake in central China, nearly 400 years later. In 1920, a large earthquake in Haiyuan, in the Ningxia Authority of northern Shaanxi Province, caused about 675 major landslides in deposits of loess, killing another 100,000-200,000 people. Further south in 2008, the May 12 magnitude 7.9 earthquake in Sichuan Province similarly initiated massive landslides that killed an estimated 87,587 people.