Since the birth of the Earth, the planet has slowly formed the current ellipse in countless magmatic bursts and crustal movements. The proper distance from the sun has formed four seasons. The birth of the moon moon has formed a tidal wave and formed life under many conditions... ... However, the continuous movement of the earth's crust and the new birthplace of life on this planet also brought about a devastating disaster. In the long period of time, human settlements migrated with the landforms formed by the plate movement and gradually stabilized in the past thousand years.
Then, what is the connection between the city and the earthquake? See below.
Most of the earthquakes occurred on the plate boundary. At present, most of the plate boundaries are the boundaries of the oceanic and continental crusts. The oceanic crust subducts below the continental crust and releases large amounts of energy through tectonic movements. Therefore, most earthquakes occur in subduction zones, such as the Pacific plate and Eurasian. Subduction zone of the plate. In addition, there are island arcs formed near the subduction zone, such as today's Japan - Ryukyu - Taiwan - Philippines, so the earthquakes in these places are very frequent.
Global Earthquake Structure
As the oceanic crust continues to dive under the continental crust, the two continental crusts that are separated by the oceanic crust are getting closer and closer. Land-to-land collisions occur eventually, so there is also a boundary between continental and continental crusts, such as the famous Eurasia continent. The Himalayan orogenic belt caused by the collision of the Indian mainland and the Tibetan Plateau. Therefore, the Qinghai-Tibet Plateau and surrounding areas are very prone to earthquakes.
In addition to this plate boundary, there are many small blocks, and block boundaries are also places where earthquakes are very prone to occur.
At present, China can be divided into several large blocks and some small sub-blocks. The boundary of these blocks is also some active fault zones with more domestic earthquakes.
Chinese activity map
Second, why did cities avoid the earthquake zone?
With such a short history of mankind, the choice of city location is not really related to the earthquake. Instead, it is related to the flood.
At present, the recurrence period of magnitude 7 earthquakes is basically more than 1,000 years. Earthquakes such as the Wenchuan earthquake have a recurrence period of around 3,000 years. Therefore, the history of human beings of such a short history, the same city, the possibility of experiencing several major earthquakes is almost non-existent, so it is not practical to escape the earthquake disaster and relocate the city.
The formation of cities is closely related to economic and cultural development.
Earthquakes are a manifestation of tectonic movements. In regions where tectonic movements are strong, they generally rise up and become mountains. Mountainous regions are often unsuitable for agricultural production. Without sufficient land resources to carry large numbers of people, there is no way to form cities. Earthquakes with relatively weak tectonism will form vast expanses of plains under the action of sedimentation. They are very suitable for the development of agriculture, increase the population, and then form cities. Therefore, most cities are coincidentally established in places where earthquakes are rare.However, there are exceptions. Tectonic movements, with uplift, will decline. In places of decline, small break basins are often formed. With basins, it is sufficient to develop into a city. Today's Ordos blocks are surrounded by a series of fault basins, including the Weihe Basin (Xi'an), Yinchuan Basin, Hetao Basin (Baotou, Hohhot), Taiyuan Basin and Linfen Basin. These local earthquakes are relatively frequent, such as the Earthquake of magnitude 8.25 in Hua County near Xi'an in 1556 , the Hongdong 8.0 earthquake in Lincang in 1303 , and the Pinglu 8.9 earthquake in Yinchuan in 1739 . Therefore, a small number of cities were established on seismic belts.
in conclusion:
1. The long recurrence cycle of the major earthquakes and the temporary civilization of mankind have determined that they have little impact on the city's site selection.
2. In the eastern plain area where China's tectonic movement is weak, there are enough land resources to carry a large number of people to form cities. Therefore, most cities are accidentally built in places where earthquakes are rare; in some areas where tectonic movement is strong, development will occur. Some small basins are enough to form cities, so a few cities are built on seismic belts.
The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.
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