What is a Seismic Zone?

Seismic belts refer to areas where earthquakes are concentrated. There are three main seismic belts on the earth-the Pacific Rim, the Mediterranean Sea, and the ridge seismic belt. The seismic zone is basically at the plate boundary, the epicenter is dense in the seismic zone, and the earthquake distribution outside the zone is scattered. Seismic zones are often associated with certain seismic structures.

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According to the global tectonic plate theory,

China is located between the world's two major seismic belts, the Pacific Rim seismic belt and the Eurasian seismic belt. Extruded by the Pacific Plate, the Indian Plate, and the Philippine Sea Plate, seismic fault zones are very developed. Since the 20th century, nearly 800 earthquakes of magnitude 6 or above have occurred in China, covering all provinces, autonomous regions, and municipalities except Guizhou, Zhejiang, and Hong Kong Special Administrative Region. China is a country with severe earthquakes with high frequency of earthquake activity, high intensity, shallow earthquake source and wide distribution. Since 1900, the number of people killed in earthquakes in China has reached 550,000, accounting for 53% of the death toll in the world. Since 1949, more than 100 destructive earthquakes have hit 22 provinces (autonomous regions and municipalities), including eastern regions. More than 270,000 people were killed in 14 provinces, accounting for 54% of the death toll from various disasters across the country. The area affected by the earthquake reached more than 300,000 square kilometers, and 7 million houses collapsed. The severity of earthquakes and other natural disasters constitutes one of China's basic national conditions. Chinese earthquakes are mainly distributed in five regions: Taiwan, Southwest, Northwest, North China, Southeast Coastal and 23 earthquake zones.
China's earthquake activity is mainly distributed in 23 seismic zones in six regions. The six regions are: Taiwan Province and its adjacent seas; Southwestern regions, mainly Tibet, western Sichuan, and central and western Yunnan; Northwestern regions, mainly in the Hexi Corridor of Gansu, Qinghai, Ningxia, and the northern and southern foothills of Tianshan; North China Areas are mainly on both sides of Taihang Mountain, Fenwei River Valley, Yinshan-Yanshan area, central Shandong and Bohai Bay; Guangdong, Fujian and other places along the southeast coast; Jilin and eastern Heilongjiang. China's Taiwan Province is located in the Pacific Rim earthquake zone, Tibet, Xinjiang, Yunnan, Sichuan, Qinghai and other provinces are located in the Himalayan-Mediterranean earthquake zone, and other provinces are in related seismic zones. The distribution of China s earthquake zones is an important basis for the establishment of China s key surveillance and defense areas for earthquakes.

Pacific Rim Volcanic Seismic Belt

See also: Pacific Rim Seismic Belt

The distribution of earthquakes is regular. Earthquakes in the world are mainly concentrated in three major seismic belts, namely: the Pacific Rim seismic belt, the Eurasian seismic belt (Mediterranean-Himalayan belt), and the ridge seismic belt. ^[1]

The Pacific Rim Seismic Belt is the most important seismic belt on the earth. It resembles a huge ring distributed around the Pacific Ocean. It travels south along the Pacific coast of North America, Alaska in the United States, southward, and passes through Canada Headquarters, California, and western Mexico. Columbia, Peru, and Chile in the Americas, then turned west from Chile, crossed the Pacific Ocean and reached near the eastern border of Oceania, turned north in the eastern waters of New Zealand, and then passed Peiji, Indonesia, the Philippines, Taiwan Province of China, the Ryukyu Islands, the Japanese Islands, The Thousand Islands, Kamchatka Peninsula, Aleutian Islands, returned to Alaska in the United States, circled the Pacific Ocean, and separated the continent from the ocean. About 80% of earthquakes on the planet occurred here. The former has concentrated more than 80% of the world's shallow-source earthquakes (0 to 70 kilometers), almost all of the middle-source (70-300 kilometers) and deep-source (300-700 kilometers) earthquakes.

Earthquake on the Qinghai-Tibet Plateau

"Qinghai-Tibet Plateau earthquake zone" includes Kush Mountain, Xingdu Mountain, West Kunlun Mountain, Alkin Mountain, Qilian Mountain, Helan Mountain-Liupan Mountain, Longmen Mountain, involving all or part of Qinghai, Tibet, Xinjiang, Gansu, Ningxia, Sichuan, Yunnan, And parts of the former Soviet Union, Afghanistan, Pakistan, India, Bangladesh, Myanmar, Laos and other countries.

This earthquake area is the largest earthquake area in China, and it is also the area with the strongest earthquake activity and frequent earthquakes. According to statistics, there were 9 earthquakes of magnitude 8 or above; 78 earthquakes of magnitude 7-7.9. Both rank first in the country.

Southeast coast of earthquake zone

Distribution of the seismic belts along the southeast coast of China: Geographically, the seismic belts along the southeast coast mainly include Fujian, Guangdong provinces, and a small part of Jiangxi and Guangxi. This seismic zone is controlled by the north-east active faults of the Xinhuaxia system that are approximately parallel to the coastline. In addition, some north-west active faults also play a certain role in the formation of seismic conditions. From the east to the west, this group of northeast active faults are: Changle-Zhao'an fault zone, Zhenghe-Haifeng fault zone, and Shaowu-Heyuan fault zone. Many destructive earthquakes occurred along the fault zone. For example, along the Changle-Zhao'an fault zone, a magnitude 8 earthquake in Quanzhou overseas and a series of strong earthquakes near Nan'ao occurred; Huichang 6.0 occurred in the Shaowu-Heyuan fault zone Magnitude (1806) earthquake, the Heyuan magnitude 6.1 (1962) earthquake and the Xunwu magnitude 5.8 (1987) earthquake. The Zhenghe-Haifeng fault zone also experienced destructive earthquakes, but the total intensity was relatively low.

North-South earthquake zone

From Ningxia, China, through eastern Gansu, western Sichuan, and Yunnan, there is an earthquake-intensive zone that runs through mainland China and is roughly in the north-south direction. The belt extends north to Mongolia and south to Myanmar. An earthquake of magnitude 8.0 on May 12, 2008 in Wenchuan, Sichuan, occurred in this earthquake zone.

Earthquake zone other

In addition, the "Xinjiang earthquake zone" and "Taiwan earthquake zone" are also two earthquake zones in China that had a magnitude 8 earthquake. It is also well known that there are constant strong destructive earthquakes here. Due to the quake zone in Xinjiang as a whole, the population is scarce and the economy is underdeveloped. Although there are many strong earthquakes and they are more frequent, most earthquakes occurred in mountainous areas, and the human and property losses caused by them were much smaller than those of several earthquake zones in eastern China.