Tangshan earthquake

Earthquake

Date: July 28, 1976

Place: Tangshan, northeastern China

Magnitude: 8.0

Result: About 250,000 dead (the highest death toll for a natural disaster in the twentieth century), 160,000 seriously injured, almost the entire city of 1.1 million people destroyed

China has a long recorded history of earthquakes. Geologically, it is a region of complex tectonic relationships. The Indian Plate is pushing northward in the southwest, forming the Himalayas and elevated Tibetan Plateau, and oceanic plates are approaching and colliding in the southeast and east.

Historically, China is a vast region that has had a large population for millennia, as well as a relatively advanced culture, with recorded history extending back well over two thousand years. When the Communist Party took power in 1949 and the People’s Republic of China began, a search was initiated by 130 historians to document the history of seismic activity. They found that there had been more than ten thousand earthquakes recorded in China in the previous three thousand years—over five hundred of them of disaster proportions.

Setting. Tangshan is a large, thriving industrial city at 39.4 degrees north latitude and 118.1 degrees east longitude in Hebei Province of northeast China, 100 miles (160 kilometers) southeast of the capital of Beijing. It is about 25 miles (40 kilometers) from the Gulf of Chihli, on the Yellow Sea. Its name derives from the T’ang dynasty (618-907 c.e.) and the word for mountains, “shan.” In the early 1970’s it had a population of 1.1 million, much industrial production, and China’s largest coal mine, at nearby Kailuan. There was little expectation that Tangshan was to become the site, in terms of death and destruction, of the worst natural disaster of the twentieth century, with the second highest death toll in the recorded history of earthquakes—exceeded only by a great earthquake in January, 1556, in Shaanxi (or Shensi), central China, in which 830,000 died when buildings and caves collapsed at night.

The important Beijing-Tianjin-Tangshan region of northeast China was being intensely studied for potential seismic risk. By the early 1970’s the Chinese government had begun a major effort to investigate earthquake prediction, using the State Bureau of Seismology, other agencies, and an extensive network of field stations to monitor various geophysical and geological properties of the local earth, which were thought to be possible precursors that might herald an impending earthquake. This effort resulted in a spectacular success in 1975, when seismologists detected an increasing frequency of minor earthquakes in the region of Haicheng, northeast of Tangshan, along with some regional ground deformation. They thought this could indicate an upcoming, larger earthquake.

On February 4, 1975, their warning resulted in the evacuation of well over 1 million people from their homes, factories, and other workplaces—into the cold, without civil resistance. A few hours later, at 7:36 p.m., the Haicheng area was hit by a magnitude 7.3 earthquake, which destroyed 90 percent of the buildings of Haicheng as well as nearby towns and villages. There were only 1,328 deaths, however, compared to the doubtless tens of thousands who would have died without the advance warning and evacuation. A later report noted that the seismologists who had predicted the quake were “worshipped as saviours.”

Unfortunately, nature would not easily yield its secrets and intentions. Despite much work in earthquake prediction in seismically active areas in the United States, Japan, Russia, and China, Haicheng remained the only major earthquake that had been predicted correctly—or with a short-term notice—by the year 2000. After the Haicheng event, various seismic stations in China issued their own predictions for local earthquakes, but none occurred.

The Tangshan area had likewise been monitored since 1974 for changes in such conditions as microseismicity (number and location of very small earthquakes), ground elevation, local sea level, gravity and magnetic fields, radon gas in groundwater, and even drought conditions. There was sufficient concern that on July 15, 1976, there was a meeting of technical experts in Tangshan. However, it was felt that there was no indication of potential seismic activity exceeding magnitude 5, which was the threshold at which it would be reported to the civil authorities. Some thought an earthquake might be possible in the next few years, but there were no minor precursory foreshocks warning that a quake was imminent. There were also meetings in Beijing of the State Bureau of Seismology on July 24 and 26, regarding the possibility of a future earthquake in the Beijing-Tianjin-Tangshan area. While there was no technical reason for immediate concern, it was also true that an alert leading to evacuation would be very disruptive to life, production, and other economic activity in the large cities in the region.

Since the area is of intraplate nature, which is far away from the seismically and tectonically active margins of the crustal plates, earthquakes there are expected to be infrequent and of only moderate size. Human knowledge of crustal fracturing, stress, and potential for faulting (slippage, which causes earthquakes) is imperfect. There had been major earthquakes in the general region of Tangshan in September, 1679, and in September, 1290 (with 100,000 deaths).

The Quake. Without warning, at 3:42 a.m. on July 28, 1976, a massive earthquake struck the Tangshan area. There was a loud rumbling and roaring sound, followed by violent jerking back and forth. The earthquake (including subsequent aftershocks) leveled 20 square miles (50 square kilometers) of the densely populated industrial center of the city, flattened or severely damaged 97 percent of the buildings and three-quarters of Tangshan’s 916 multistory structures (only 4 remained essentially intact), and left a ruin of crumbled buildings, fallen smokestacks, and rubble. Falling buildings, cement floor slabs, and beams immediately crushed thousands of people. Most of the disaster’s victims survived the initial shock only to suffocate or succumb to injuries after hours and days trapped in the dusty wreckage.

There was no electrical power, no water, no telecommunication systems, no functioning hospital, no transport routes, and no immediate search and rescue help. With 300 miles of railroad track ruined, 231 highway bridges damaged, and rivers without crossings, relief could not arrive quickly. It was over a day before the first of an eventual 100,000 army troops and 50,000 others could arrive. For ten days the workers did not have the necessary heavy equipment and cranes to clear the rubble and retrieve many people.

The city was initially shrouded in total darkness (it being nighttime) and a dense gray fog of soil, coal dust, and smoke. According to the local Chinese authorities, 242,769 people died and 164,851 were seriously injured. Other reports and international databases listed the official death toll as 250,000 to 255,000, and early estimates by visitors placed it even higher.

The earthquake had a magnitude of 7.8 as determined by Chinese seismologists, and 8.0 in the international database maintained by the U.S. Geological Survey/National Earthquake Information Center. Its focus, where rupture began, was at a relatively shallow depth of 14 miles (23 kilometers), and its epicenter was calculated at 39.5 degrees north and 117.9 east—virtually right under Tangshan. Later that same day, at 6:45 p.m. on July 28, there was a major aftershock, with magnitude 7.4 at the same focal region. It finished off most of the buildings that had survived the first shock. Within forty-eight hours of the initial earthquake, there were more than nine hundred aftershocks having magnitude of at least 3.0, including sixteen with magnitude at least 5.0.

Aftereffects. A second disaster was averted at the large Douhe River reservoir 9 miles (15 kilometers) northeast of Tangshan. The embankment dam was cracked and weakened, and if it collapsed it would have flooded the city. Furthermore, after the earthquake a heavy rain started, and the water level was rising. The floodgate could not be opened quickly to let out the reservoir water gradually and unstress the dam, because its electrical power was disabled. Fortunately, troops working manually for eight hours managed to get the floodgate open.

At the large coal mine complex, about 10,000 people were in the underground workings when the earthquake struck. The surface buildings were destroyed, but the large-amplitude surface wave vibrations—usually the most damaging of the seismic waves—became less intense with depth, and the deep workings were somewhat less affected. However, there was no electricity, no hoist cages for workers, and no water pumps to keep the workings from flooding with groundwater. Remarkably, only 17 mine workers died; the others managed to dig through the rubble and climb to safety or be rescued. Five men were brought up alive after fifteen days, having no food and only filthy water to drink.

Relief and Reconstruction. The search and recovery of bodies was a slow and difficult task, with the stench of decaying bodies of people and animals, lack of clean water and sanitation, and increasing danger of an epidemic. Relief aid (clothing, tents, heavy equipment, and medical supplies) was offered by the United Nations, the United States, Great Britain, Japan, and others, but the Chinese government declined it. In retrospect, this denied timely and useful assistance. However, at the time, China was in its Cultural Revolution—a decade-long era which would last until September, 1976, when Chairman Mao Zedong died—and the Chinese wanted to display their self-reliance and not engender a dependent mentality and considered any outsiders and their assistance to be “interference by others.”

It was also not an easy time for the State Bureau of Seismology and those engaged in earthquake monitoring and prediction. When the earthquake occurred, the recording seismographs in Beijing were driven off the scale by the large vibrations, and others around the country could not pinpoint the epicenter other than being somewhere around Beijing. So, with much of the telecommunication systems in the area disabled, scientists set out in vehicles in all directions to try to find the epicenter and greatest damage. After being credited with the success of predicting the Haicheng earthquake the previous year, the seismologists became ridiculed, and the failure to predict the devastating Tangshan event became blame for negligence. Anger and abuse were directed at those identified locally as earthquake experts, as if the inability to reliably predict one of nature’s great uncertainties was somehow willful and deserving of punishment.

Within two years, a massive reconstruction effort had restored the city’s industrial production to what it had been. By 1986, ten years after the earthquake, restoration was mostly complete, although some citizens were still in temporary shelters, and the population of Tangshan had increased to 1.4 million. Because it was now recognized that the city was on a major crustal fault, reconstruction was carried out to make structures more earthquake-resistant. Water pipes were made with flexible joints so they could withstand vibration, embankments were reinforced around nearby reservoirs, and hazardous industries were moved outside of town. One factory that had been destroyed in the great earthquake has been left as a memorial to the thousands lost.

Bibliography

Chen, Yong, et al., eds. The Great Tangshan Earthquake of 1976: An Anatomy of Disaster. New York: Pergamon Press, 1988.

De Blij, H. J. Nature on the Rampage. Washington, D.C.: Smithsonian Institution, 1994.

Housner, George W., and He Duxin, eds. The Great Tangshan Earthquake of 1976. Pasadena: California Institute of Technology, 2004.

Qian Gang. The Great China Earthquake. Translated by Nicola Ellis and Cathy Silber. Beijing: Foreign Language Press, 1989.

Reese, Lori. “Tangshan: Earthquake, July 28, 1976—An Ominous Rumbling.” Time Asia 154, no. 12 (September 27, 1999).

Sun, Youli. Wrath of Heaven and Earth: Chinese Politics and the Tangshan Earthquake of 1976. New York: St. Martin’s Press, 2006.