Review and Changes of Quanzhou Earthquake

Fu Bihong from Zhongshan Middle School

On the evening of 2 1 May, 2003, an earthquake measuring 6.2 on the Richter scale occurred in northern Algeria. Subsequent aftershocks killed 2,274 people, injured more than 10,000 people and caused property losses of 5 billion US dollars. I'm sorry to hear that. Among the 5 million earthquakes that occur every year in the world, only about 10 earthquakes can really cause serious harm to human beings every year. However, mankind has paid a very heavy price for this. In the recent 20th century, thousands of destructive earthquakes hit many countries and regions in the world, causing about 6.5438+0.5 million deaths and countless huge economic losses. The severity of earthquake disaster and the size of casualties and economic losses depend on many factors, such as magnitude, place and time (day or night). Focal depth, earthquake type, surface or fault rupture scale, urban seismic fortification, building (structure) quality, site conditions, seismic capacity, type and scale of earthquake secondary disasters, earthquake prediction level and human awareness of disaster prevention and mitigation, etc. Generally speaking, the greater the magnitude of an earthquake, the greater its harmfulness. But there are two other exceptions. First, some earthquakes even have magnitude. However, because they occur in the sea far away from cities or sparsely populated mountainous areas, they may not necessarily cause major disasters. For example, 195 1, 1997 Dangxiong earthquake in Tibet, Mani earthquake in China, etc., all belong to this kind of major earthquake and minor disaster. Secondly, although some earthquakes are small in magnitude, they occur under densely populated cities. In addition, shallow focal point or poor site conditions, or the impact of unguarded cities and poor seismic performance of buildings often cause great disasters. There are many examples of such small earthquakes and disasters in the 20th century, especially in the second half of this year. For example, the China 1979 earthquake with magnitude 6 in Liyang killed 42 people, injured more than 3,000 people and lost 200 million yuan. 65438+1September, 1993, an earthquake of magnitude 6.2 in India killed 30,000 people; 1999 Armenia, Colombia earthquake of magnitude 5.7, with 6,700 casualties; A 4.2-magnitude earthquake struck southern Bangladesh, killing more than 200 people; In Athens, Greece, an earthquake with M = 5.9 killed 88 people and injured 24 others. These earthquakes have a common feature: almost all of them occurred in or near cities, thus causing serious disasters. In fact, in the last century, more and more earthquakes, including many large earthquakes with M = 7 or above, occurred directly below the city. These direct earthquakes have caused many cities in the world, such as San Francisco, USA. Tokyo, Hanshin, adana, Izmit, Almaty, southern Guatemala, Eljintra, Mexico City, Pitak, Armenia, etc. , have suffered extremely heavy damage, shocked the world and attracted worldwide attention. Urban earthquake disaster has become an important factor that seriously affects and restricts regional economic and social development, which is also the reason why many countries in the world have always attached importance to cities, especially big cities.

The heavy losses caused by earthquakes are sometimes not all direct disasters caused by earthquakes, that is, the destruction of buildings and engineering facilities caused by strong ground vibration and ground rupture and deformation. Losses caused by secondary disasters caused by earthquakes, such as fires, floods, tsunamis, landslides and mudslides. , is often serious, sometimes even more than the losses caused by direct disasters. For example,1960 May 21~ June 22, the largest earthquake swarm occurred in Chile in the 20th century. The earthquake swarm consists of 7 earthquakes with magnitude above 7, including 2 earthquakes with magnitude above 8, with the maximum magnitude of 8.5. Successive major earthquakes triggered a landslide in Lake Reni, which filled the lake basin, causing the lake to rise and overflow, flooding the city of Valvia. At the same time, the earthquake also triggered a huge tsunami. Most coastal buildings in Chile were swept away by the waves, destroying 6.5438+0.6 million buildings. In addition, the waves swept across the Pacific Ocean at a speed of 600-700 kilometers per hour, washing away more than 65.438+0,000 houses along the coast of Japan and flooding more than 20,000 mu of fertile land. 150,000 people are homeless. The Diexi M = 7.5 earthquake in China1August, 933 also caused a huge flood disaster, which was also the largest earthquake flood in the history of China. During the earthquake, the mountain collapsed and blocked the Minjiang River. After 45 days, the dam burst, the river roared down, washed away countless houses, drowned more than 20 thousand people and washed away more than 50 thousand mu of fertile land. These examples of earthquakes warn that

The magnitude of earthquake losses is closely related to whether reasonable seismic design and measures are taken and the quality of buildings. The positive and negative earthquake examples in the 20th century show that earthquake resistance of structures is an effective way to reduce earthquake losses. In China, there are many similar earthquake examples. For example, strong earthquakes of magnitude 6.8 and 6./kloc-0 occurred in Xingtai, Hebei and Yanggao, Datong, Shanxi, respectively, causing serious casualties and house damage, but reasonable seismic fortification standards were adopted in post-earthquake recovery and reconstruction. Results When 198 1 and 1996 respectively suffered another devastating earthquake with magnitude of 5.8, the buildings in the earthquake-stricken area stood the test and suffered the least loss. Another example is Dongchuan City, Yunnan Province, a newly developed city after the founding of the People's Republic of China. Because of poor seismic design and measures, it suffered losses when it was hit by a strong earthquake in February 1966. A series of major earthquakes in Turkey and Taiwan Province Province also show that buildings designed according to the new seismic code or more reasonable seismic code have a lower degree of damage, while buildings designed according to the old code or not strictly according to the reasonable code have a higher degree of damage. But at the same time, some modern structures, such as railways and highway viaducts, which were originally thought to be able to withstand major earthquakes, were also damaged to varying degrees in the earthquake. These comprehensive conditions show that the task of human beings in structural earthquake resistance is still very arduous, and it needs to be continuously improved and developed on the basis of summing up experience. In addition, the Izmit earthquake in Turkey also exposed the serious problem of poor building quality, causing casualties and property losses. This is due to the construction contractor's cutting corners, fraud, government departments and their staff.