Review of the vicissitudes of the Quanzhou earthquake

Fu Bihong, Zhongshan Middle School

On the evening of May 21, 2003, an earthquake measuring 6.2 on the Richter scale occurred in northern Algeria and several subsequent aftershocks, killing 2,274 people and more than 10,000 people. People were injured and property losses amounted to US$5 billion. Hearing this news makes people sigh with regret. Among the approximately 5 million earthquakes that occur around the world every year, the average number of major earthquakes that can actually cause serious harm to humans is only about 10 per year. But mankind has paid a very heavy price for this. In the past twentieth century, thousands of devastating earthquakes have struck many countries and regions around the world, causing about 1.5 million deaths and Uncountable huge economic losses. The severity of earthquake disasters and the size of casualties and economic losses depend on many factors, such as the magnitude of the earthquake, location, time of occurrence (day or night), focal depth, earthquake type, surface Or the scale of fault rupture, the city's earthquake defense situation, the construction quality of buildings (structures), site conditions, earthquake resistance, the types and scale of secondary disasters induced by earthquakes, as well as the level of earthquake prediction and human disaster prevention and reduction The level of awareness, etc. Generally speaking, the greater the magnitude of an earthquake, the greater its harm. But there are two exceptions. One is that even if some earthquakes are large in magnitude, they occur far away from the city. They may not necessarily cause major disasters in sea areas or sparsely populated mountainous areas. For example, my country's Tibet Damxung magnitude 8 earthquake and Mani 7.5 magnitude earthquake in 1951 and 1997 are all such major earthquakes. The situation of small disasters. The second is that although some earthquakes are small in magnitude, they often occur due to the impact of factors such as occurring under densely populated cities, shallow source or poor site conditions, or due to undefended cities and poor seismic resistance of buildings. Can cause great disasters. There were many examples of such small earthquakes and major disasters in the 20th century, especially in the second half of the twentieth century. For example, in 1979, the 6-magnitude earthquake in Liyang, my country, killed 42 people, injured more than 3,000 people, and caused losses of 200 million. RMB; In September 1993, a 6.2-magnitude earthquake occurred in India, killing 30,000 people; in 1999, a 5.7-magnitude earthquake occurred in Armenia, Colombia, causing 67,000 casualties; a 4.2-magnitude earthquake in southern Bangladesh, causing more than 200 casualties; a 5.9-magnitude earthquake in Athens, Greece, killing 88 people , injuring 24 people. One common feature of these earthquakes is that they almost all occur in or near cities, thus causing serious disasters. In fact, in the past century, more and more earthquakes Earthquakes, including many major earthquakes with magnitudes above 7, have occurred directly beneath cities. These direct earthquakes have affected many cities in the world, such as San Francisco and Los Angeles in the United States, Haiyuan and Tangshan in China, Tokyo in Japan, Hanshin, Adana in Turkey, and Iraq. Zmit, Almaty, Kazakhstan, Ecuintras Sur in Guatemala, Mexico City, Spitak, Armenia, etc., have all suffered extremely heavy damage, with great social impact, severe harm, casualties and The huge property losses shocked the world and attracted worldwide attention. Urban earthquake disasters have become an important factor that seriously affects and restricts regional economic and social development. This is why many countries in the world have always regarded cities, especially large cities, as earthquake prevention, earthquake resistance and The reason for the focus of disaster reduction work.

Heavy losses caused by earthquakes are sometimes not all caused by direct disasters caused by earthquakes, that is, damage to buildings and engineering facilities caused by strong ground shaking and surface rupture and deformation. The losses caused by secondary disasters such as fires, floods, tsunamis, landslides, landslides, mudslides, etc. caused by earthquakes are often serious, and sometimes even exceed the losses caused by direct disasters. For example, May 21-6, 1960 On March 22, the largest earthquake swarm in the twentieth century occurred in Chile. The earthquake swarm consisted of seven earthquakes with magnitudes above 7, including two earthquakes with magnitudes above 8, and the maximum magnitude was 8.5. Continuous major earthquakes occurred in Switzerland. A large landslide was triggered in the Lake Neighbor area. The landslide filled the lake basin, causing the lake water to rise and overflow, flooding the city of Valdivia and leaving 1 million people homeless in the city. At the same time, the earthquake also caused a huge tsunami. , most of the buildings along the coast of Chile were swept away by the waves, destroying 160,000 houses. In addition, the waves moved at a speed of 600 kilometers to 700 kilometers per hour.

Sweeping across the Pacific Ocean, more than 1,000 homes along the coast of Japan were washed away, more than 20,000 acres of farmland were submerged, and 150,000 people became homeless. The 7.5-magnitude Diexi earthquake in my country in August 1933 also caused huge flood disasters , this is also the largest earthquake and flood in the history of our country. The earthquake caused a mountain collapse and blocked the Minjiang River. The blockage collapsed 45 days later, and the river roared down, destroying countless houses, drowning more than 20,000 people, and washing away more than 50,000 fertile fields. Mu. These earthquake cases warn us that while we are well prepared for direct earthquake disasters, we should also pay special attention to the effective prevention and control of secondary disaster sources that may be induced. This is especially important for cities that are prone to fires during earthquakes.

The magnitude of earthquake losses is closely related to whether the building adopts reasonable seismic design and anti-seismic measures, as well as the quality of construction. Both positive and negative earthquake examples in the 20th century illustrate that structural seismic resistance is the key to reducing earthquake losses. Effective ways. In my country, there are many similar earthquake cases. For example, strong earthquakes with magnitudes 6.8 and 6.1 occurred in the Xingtai area of ??Hebei Province and the Yanggao area of ??Datong, Shanxi Province in 1966 and 1989 respectively, causing serious casualties and house damage, but Both places adopted reasonable seismic fortification standards during post-earthquake recovery and reconstruction. As a result, when destructive earthquakes of magnitude 5.8 hit the two places again in 1981 and 1996, the houses in the earthquake area withstood the test with minimal losses. Another example is, Dongchuan City in Yunnan Province is an emerging city that developed rapidly after the founding of the People's Republic of China. Due to the seismic design and measures taken into consideration during construction, when it suffered a strong earthquake in February 1966, the damage was very small. In recent years, in Japan, Turkey and Taiwan, my country A series of major earthquakes in places such as China have also shown that buildings designed according to new seismic codes or more reasonable seismic codes will suffer less damage, while buildings designed according to old codes or not strictly in accordance with reasonable codes will suffer low damage. However, at the same time, some modern structures that were originally thought to be able to withstand major earthquakes, such as railways and highway viaducts, were also damaged to varying degrees during the earthquake. These circumstances comprehensively show that human beings still have a very arduous task in structural earthquake resistance. It is necessary to continuously improve and develop on the basis of summarizing experience. In addition, major earthquakes such as Izmit in Turkey have also exposed serious problems of casualties and property losses caused by poor quality of buildings. This is because construction contractors cut corners and commit fraud, and government departments and The human tragedy caused by inadequate supervision and even neglect of duties by its staff should be taken as a special warning in project construction.