Tangshan Earthquake (1976)

On July 28, 1976, at 3:42 A.M., a destructive 7.8-magnitude earthquake struck the densely populated city of Tangshan. The nearby cities of Tianjin and Beijing were affected with partial destruction occurring in Tianjin and minor damage in Beijing. The official death toll stands at 242,000. Over 500,000 were injured, with over 7,000 households completely destroyed. Although there were no obvious precursory events, a midterm prediction of an imminent earthquake had been issued by scientists.

An important industrial city, home to one million people, Tangshan is situated in the Hebei province of China and located 93 miles east of Beijing. Since 1485, 22 earthquakes of magnitude 4.5 or above have occurred in the region. In the 10 years prior to the 1976 quake, earthquake activity began to increase. Two years prior to the earthquake, officials in northeast China were warned about the risk of seismic activity in the next 10 years, concluding that a magnitude 5–6 quake may occur within the next two years. Document 69 was produced by the China Earthquake Agency and forecasted the long-term likeness of increased seismic activity. The publication also included information for earthquake preparedness and mitigation measures. Six months before the Tangshan quake, a series of earthquake swarms occurred around Tangshan and Tainjin.

The earthquake lasted 10–16 seconds, rupturing 62 miles of the Tangshan fault and resulting in horizontal displacements of up to five-feet in lower Tangshan. Magnitude 5.5 aftershocks occurred, and two particularly large aftershocks known as the Luanxian and Ningho earthquakes followed in the months after the initial quake. These quakes collectively make up the Tangshan earthquake sequence. Prior to the earthquake, Tangshan's population stood at 1.2 million. An additional 2 [Page 667]million inhabitants were located 25 miles from the epicenter, and 5.5 million lived across the region. The official death toll stands at 242,000; 140,000 from Tangshan alone. Many believe the figure to be far greater, with estimates reaching in excess of 700,000. Economic losses were estimated at $10 billion (1976 rate).

Due to intense ground shaking, the majority of the city's brick buildings collapsed, burying thousands of residents who were asleep. China's seismic building design code was first published in 1955. The updated, 1974 code designated Tangshan as a region of low seismicity, and therefore buildings were constructed with no regard for seismic design or resistance. Buildings ranged from older stone wall, unreinforced brick, and masonry structures, to newer, reinforced concrete frame construction. Lesser damage occurred in areas where soil deposits consisted of rock. The infrastructure was devastated with roads, bridges, railways, telegraph systems, water supplies, and power sources completely destroyed, leaving Tangshan isolated from the outside world. The nearby cities of Beijing and Tianjin also suffered varying amounts of damage. Older wood and brick structures in Tianjin suffered heavy damage, whereas newer concrete and brick structures were more robust, suffering mild damage.

A number of factors contributed to the excessive death toll. First, the earthquake struck nine miles directly beneath the city. The earthquake also occurred when the majority of inhabitants were asleep, when they did not have any time to react; many were buried underneath the ruins of their homes. The quality and standard of buildings were not designed with earthquakes in mind, and were of substandard quality, built with heavy, flat roofs.

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