There are many reasons for the vibration of the earth's surface. According to the causes of earthquakes, earthquakes can be divided into the following categories:
1, tectonic earthquake
Long-term accumulated energy is released sharply due to the fracture and dislocation of rocks in the deep underground, and spreads in all directions in the form of seismic waves. The ground motion caused by the ground is called tectonic earthquake. This kind of earthquake has the highest frequency and the greatest destructive power, accounting for more than 90% of the global earthquakes.
2. Volcanic earthquake
Earthquakes caused by volcanism, such as magmatism and gas explosion, are called volcanic earthquakes. Volcanic earthquakes can only occur in volcanic active areas, and earthquakes in volcanic active areas only account for about 7% of global earthquakes.
3. Collapse earthquake
An earthquake caused by the collapse of an underground cave or mine top is called a collapse earthquake. Such earthquakes are relatively small in scale and few in frequency. Even if it exists, it often occurs in limestone areas with dense caves or large underground mining areas.
4. Induced earthquake
Earthquakes caused by reservoir impoundment and oil field water injection are called induced earthquakes. This kind of earthquake only occurs in some specific reservoir areas or oil fields.
5. Artificial earthquake
The ground vibration caused by underground nuclear explosion and explosive blasting is called artificial earthquake. Artificial earthquakes are earthquakes caused by human activities. Such as vibration caused by industrial blasting and underground nuclear explosion; High-pressure water injection in deep wells and water storage in large reservoirs increase the pressure on the earth's crust and sometimes induce earthquakes.
A new theory of earthquake genesis
Genetic theory of earthquake nucleation
Earthquakes are the manifestation of the timely influence of mantle nuclear changes on the crust. The long-term precipitation, precipitation and stratification of the mantle have formed a relatively pure nuclear fission (such as uranium) material circle in the depths of the earth. At the same time, due to the long-term precipitation of the mantle or the generation and precipitation of internal substances or the inhalation and pyrolysis of liquid and gaseous substances (such as seawater, oil and air) on the earth's surface, relatively pure nuclear fusion substances (such as hydrogen) have gathered in the upper mantle (between the mantle and the crust). Convection in the mantle makes nuclear fission materials meet and exceed the critical volume, leading to nuclear fission (if there is nuclear fusion material nearby at this time), which in turn leads to nuclear fusion, resulting in instantaneous rapid expansion, bouncing off the crust to produce longitudinal waves, and the longitudinal waves stretch the crust to produce shear waves. (The contents of this chapter shall not be used for relevant exam answers without the approval of authoritative organizations. )
One of the reasons for the Wenchuan earthquake is that the Indian plate subducted into the Asian plate, which caused the rapid uplift of the Qinghai-Tibet Plateau and led to the earthquake. The plateau material slowly flows eastward and squeezes eastward along the Longmenshan structural belt on the eastern edge of the plateau, encountering the tenacious resistance of the rigid block under the Sichuan basin, resulting in the long-term accumulation of tectonic stress energy, and finally suddenly released in Beichuan-Yingxiu area of Longmenshan.
Second, thrust, dextral and compressional fault earthquakes. First, the seismogenic structure is the central fault zone of Longmenshan structural belt, which is thrust from southwest to northeast under the action of compressive stress. Second, the earthquake was a one-way rupture earthquake, which moved from southwest to northeast, causing the aftershocks to spread to the northeast. Thirdly, after the main earthquake, the stress propagation and release process of the compressional thrust fault earthquake is slow, which may lead to strong aftershocks and long duration.
Causes of earthquakes Earthquakes can be divided into natural earthquakes and artificial earthquakes. In addition, earthquakes will also occur under some special circumstances, such as large meteorites hitting the ground (meteorite impact earthquake). There are many reasons for the vibration of the earth's surface. According to the causes of earthquakes, earthquakes can be divided into the following categories:
1. Due to the fracture and dislocation of rocks in the deep underground, the long-term accumulated energy is released sharply and spread in all directions in the form of seismic waves. The ground vibration caused by earthquake is called tectonic earthquake. This kind of earthquake has the highest frequency and the greatest destructive power, accounting for more than 90% of the global earthquakes.
2. Volcanic earthquake An earthquake caused by volcanism, such as magmatic activity and gas explosion, is called a volcanic earthquake. Volcanic earthquakes can only occur in volcanic active areas, and earthquakes in volcanic active areas only account for about 7% of global earthquakes.
3. Collapse earthquake An earthquake caused by the collapse of an underground cave or the top of a mine is called a collapse earthquake. Such earthquakes are relatively small in scale and few in frequency. Even if it exists, it often occurs in limestone areas with dense caves or large underground mining areas.
4. Induced earthquake An earthquake caused by activities such as reservoir impoundment and oil field water injection is called induced earthquake. This kind of earthquake only occurs in some specific reservoir areas or oil fields.
5, artificial earthquake underground nuclear explosion, explosive blasting and other human-induced ground vibration is called artificial earthquake. Artificial earthquakes are earthquakes caused by human activities. Such as vibration caused by industrial blasting and underground nuclear explosion; High-pressure water injection in deep wells and water storage in large reservoirs increase the pressure on the earth's crust and sometimes induce earthquakes.
The cause of the Wenchuan earthquake is preliminarily judged to be caused by the Indian plate.
The Indian plate subducted into the Asian plate, which led to the rapid uplift of the Qinghai-Tibet Plateau. The plateau material slowly flows eastward and squeezes eastward along the Longmenshan structural belt on the eastern edge of the plateau, encountering the tenacious resistance of the rigid block under the Sichuan basin, resulting in the long-term accumulation of tectonic stress energy, and finally suddenly released in Beichuan-Yingxiu area of Longmenshan.
Wenchuan earthquake is a thrust dextral compressional fault earthquake.
First, the seismogenic structure is the central fault zone of Longmenshan structural belt, which is thrust from southwest to northeast under the action of compressive stress. Second, the earthquake was a one-way rupture earthquake, which moved from southwest to northeast, causing the aftershocks to spread to the northeast. Thirdly, after the main earthquake, the stress propagation and release process of the compressional thrust fault earthquake is slow, which may lead to strong aftershocks and long duration.
Wenchuan earthquake is shallow earthquakes.
Wenchuan earthquake does not belong to the deep plate boundary effect, but occurred in the brittle-ductile transition zone of the crust with a focal depth of 10-20km, which is extremely destructive.
What is the main cause of the earthquake? Because the earth is constantly moving and changing, it has gradually accumulated enormous energy. In some fragile areas of the earth's crust, the strata suddenly break or the original faults move. This is an earthquake.
Earthquakes are divided into tectonic earthquakes, volcanic earthquakes, subsidence earthquakes and induced earthquakes.
Tectonic earthquake means that under the action of tectonic movement, when the local stress reaches and exceeds the strength limit of rock stratum, the rock stratum will suddenly deform or even rupture, and the energy will be released at once, causing ground motion. This kind of earthquake is called tectonic earthquake, accounting for more than 90% of the total number of earthquakes.
Volcanic earthquake refers to an earthquake that occurs in the deep underground due to the fracture or collapse of the overlying strata due to the loss of a large amount of magma, the reduction of underground pressure or the lack of time to replenish magma. The number of such earthquakes is small, accounting for only about 7% of the total number of earthquakes.
Collapse earthquake is a regional earthquake caused by underground cave or goaf collapse. Collapse earthquakes are all the results of gravity, with small scale and low frequency, accounting for only about 3% of the total number of earthquakes.
What caused the earthquake? What caused the earthquake? -
_ _ _ _ _ _ _-Natural reasons and man-made reasons!
First, the cause of the general earthquake
To put it simply, the main reason for the earthquake is that the major plates of the earth are squeezing each other, and volcanic eruption is also one of the reasons.
Earthquakes are divided into natural earthquakes and artificial earthquakes. Natural earthquakes are mainly tectonic earthquakes, which are caused by the fracture and dislocation of rocks deep underground, so that the long-term accumulated energy is suddenly released and spread in all directions in the form of seismic waves, making houses shake and move to the ground. Tectonic earthquakes account for more than 90% of the total number of earthquakes. Followed by earthquakes caused by volcanic eruptions, known as volcanic earthquakes, accounting for about 7% of the total number of earthquakes.
Artificial earthquakes are earthquakes caused by human activities. Such as vibration caused by industrial blasting and underground nuclear explosion; High-pressure water injection in deep wells and water storage in large reservoirs increase the pressure on the earth's crust and sometimes induce earthquakes.
Second, the causes of the Wenchuan earthquake
According to Zhang Guomin, a researcher at the Institute of Earthquake Prediction, Seismological Bureau of China, Wenchuan Earthquake is an internal earthquake in Chinese mainland, which belongs to shallow earthquakes and has great destructive power.
Generally speaking, the Wenchuan earthquake is located in a major seismic belt in China-the North-South seismic belt, and the central axis seismic belt is located between longitude 100 and longitude 105, covering the areas from Ningxia to eastern Gansu, western Sichuan and Yunnan, belonging to the earthquake-intensive belt in China. To Xiaoli, Wenchuan is in the Longmenshan earthquake zone in Sichuan. Therefore, the probability of an earthquake here is very high.
Erchie Wang, a researcher at the Institute of Geology and Geophysics, Chinese Academy of Sciences, said that the Wenchuan earthquake occurred on the southeast edge of the Qinghai-Tibet Plateau, in the center of Longmen Mountain in western Sichuan, and on the Wenchuan-Mao Wen fault zone. The Indian Ocean plate moved northward, squeezing the Eurasian plate, resulting in the uplift of the Qinghai-Tibet Plateau. While the plateau is uplifting, it is also moving eastward, squeezing the Sichuan Basin. Sichuan basin is a relatively stable block. Although the main body of Longmenshan looks weak in tectonic activity, it may be in the process of stress accumulation. When the stress accumulates to a certain extent, the crust will break and an earthquake will occur.
The Institute of Seismology of the University of Tokyo in Japan explained that the earthquake was located in the Longmenshan fault zone. In the past few hundred years, there have been many large earthquakes with a magnitude of more than 7 on the Richter scale near this fault zone, but before this earthquake, there was no strong activity in the main body of Longmen Mountain. The fault is distributed from northeast to southwest along the edge of Sichuan basin, with a length of 300 to 400 kilometers and a width of about 60 kilometers. It is napped on the Sichuan Basin along the Qinghai-Tibet Plateau. Because the accumulated stress exceeds the critical point of rock strength, an earthquake of magnitude 7.8 occurred in Longmenshan fault zone.
The crust is moving.