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5.7.5: Have the Chinese Found the Way to Predict Earthquakes?

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    6002
  • Overview

    Should we write off the possibility of predicting earthquakes as simply wishful thinking? Before we do so, we must first look carefully at earthquake predictions in China, a nation wracked by earthquakes repeatedly throughout its long history. More than eight hundred thousand people lost their lives in an earthquake in north-central China in 1556, and another one hundred eighty thousand died in an earthquake in 1920.

     

    During the Zhou Dynasty, in the first millennium B.C., the Chinese came to believe that heaven gives wise and virtuous leaders a mandate to rule, and removes this mandate from heaven if the leaders are evil or corrupt. This became incorporated into the Taoist view that heaven expresses its disapproval of bad rule through natural disasters such as floods, plagues, or earthquakes.

     

    In March 1966, the Xingtai Earthquake of M 7.2 struck the densely populated North China Plain two hundred miles southwest of the capital city of Beijing, causing more than eight thousand deaths. It might have been a concern about the mandate from heaven that led Premier Zhou Enlai to make the following statement: “There have been numerous records of earthquake disasters preserved in ancient China, but the experiences are insufficient. It is hoped that you can summarize such experiences and will be able to solve this problem during this generation.”

     

    This call for action may be compared to President Kennedy’s call to put a man on the Moon by the end of the 1960s. Zhou had been impressed by the earthquake-foreshock stories told by survivors of the Xingtai Earthquake, including an M 6.8 event fourteen days before the mainshock, fluctuations in groundwater levels, and strange behavior of animals. He urged a prediction program “applying both indigenous and modern methods and relying on the broad masses of the people.” In addition to developing technical expertise in earthquake science, China would also involve thousands of peasants who would monitor water wells and observe animal behavior. Zhou did not trust the existing scientific establishment, including the Academia Sinica and the universities, and he and Mao Zedong created an independent government agency, the State Seismological Bureau (SSB), in 1970.

     

    Following an earthquake east of Beijing in the Gulf of Bohai in 1969, it was suggested that earthquakes after the Xingtai Earthquake were migrating northeast toward the Gulf of Bohai and Manchuria. Seismicity increased, the Earth’s magnetic field underwent fluctuations, and the ground south of the city of Haicheng in southern Manchuria rose at an anomalously high rate. This led to a long-range forecast that an earthquake of moderate magnitude might strike the region in the next two years. Monitoring was intensified, earthquake information was distributed, and thousands of amateur observation posts were established to monitor various phenomena. On December 22, 1974, a swarm of more than one hundred earthquakes, the largest of M 4.8, struck the area of the Qinwo Reservoir near the city of Liaoyang. At a national meeting held in January 1975, an earthquake of M 6 was forecast somewhere within a broad region of southern Manchuria.

     

    As January passed into February, anomalous activity became concentrated near the city of Haicheng. Early on February 4, more than five hundred small earthquakes were recorded at Haicheng. This caused the government of Liaoning Province to issue a short-term earthquake alert. The people of Haicheng and nearby towns were urged to move outdoors on the unusually warm night of February 4. A large number of foreshocks made this order easy to enforce. Not only did the people move outside into temporary shelters, they also moved their animals and vehicles outside as well. So when the M 7.3 earthquake arrived at 7:36 p.m., casualties were greatly reduced, even though in parts of the city, more than 90 percent of the houses collapsed. Despite a population in the epicentral area of several million people, only about one thousand people died. Without the warning, most people would have been indoors, and losses of life would have been many times larger. China had issued the world’s first successful earthquake prediction.

     

    However, in the following year, despite the intense monitoring that had preceded the Haicheng Earthquake, the industrial city of Tangshan, 220 miles southwest of Haicheng, was struck without warning by an earthquake of M 7.5-7.6. The Chinese gave an official estimate of about two hundred fifty thousand people killed. Unlike Haicheng, there were no foreshocks. And there was no general warning.

     

    What about the mandate from heaven? The Tangshan Earthquake struck on July 28, 1976. The preceding March had seen major demonstrations in Tiananmen Square by people laying wreaths to the recently deceased pragmatist Zhou Enlai and giving speeches critical of the Gang of Four, radicals who had ousted the pragmatists, including Deng Xiaoping, who would subsequently return from disgrace and lead the country. These demonstrations were brutally put down by the military (as they would be again in 1989), and Deng was exiled. The Gang of Four had the upper hand. But after the Tangshan Earthquake, Chairman Mao Zedong died and was succeeded by Hua Guofeng. The Gang of Four, including Mao’s wife, opposed Hua, but Hua had them all arrested on October 6. Deng Xiaoping returned to power in 1977 and launched China’s progress toward becoming a superpower, with greatly increased standards of living for its citizens. One could say that the mandate from heaven had been carried out!

     

    Was the Haicheng prediction a fluke? In August 1976, the month following the Tangshan disaster, the Songpan Earthquake of M 7.2 was successfully predicted by the local State Seismological Bureau. And in May 1995, a large earthquake struck where it was predicted in southwestern China. Both predictions resulted in a great reduction of casualties. As at Haicheng, both earthquakes were preceded by foreshocks.

     

    Why have the Chinese succeeded where the rest of the world has failed? For one thing, Premier Zhou’s call for action led to a national commitment to earthquake research unmatched by any other country. Earthquake studies are concentrated in the China Earthquake Administration (CEA, the new name for the SSB), with a central facility in Beijing, and laboratories in every province. The CEA employs thousands of workers, and seismic networks cover the entire country. Earthquake preparedness and precursor monitoring are carried out at all levels of government, and, in keeping with Chairman Mao’s view that progress rests with “the broad masses of the people,” many of the measurements are made by volunteers, including schoolchildren.

     

    Even so, perhaps most and possibly all of the apparent Chinese success is luck. All of the successful forecasts included many foreshocks, and at Haicheng the foreshocks were so insistent that it would have taken a major government effort for the people not to take action and move outdoors on the night of February 4. The Haicheng earthquake was the largest earthquake in an earthquake swarm, whereas the Tangshan earthquake in the following year was a mainshock followed by aftershocks. No major earthquake in recent history in the United States or Japan is known to have been preceded by enough foreshocks to lead to a short-term prediction useful to society. Also, despite the few “successful” predictions in China, many predictions have been false alarms, and the Chinese have not been forthright in publicizing their failures. These false alarms are more than would have been acceptable in a Western country. In addition, the Wenchuan earthquake of M 7.9 in Sichuan Province killed more than 80,000 people. It was not predicted.