What caused the earthquake?

The main causes of earthquakes are: the earth's major plates are pressing against each other, and volcanic eruptions.

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. In addition, earthquakes will also occur in some special circumstances, such as cave collapse (collapse earthquake) and large meteorites hitting the ground (meteorite impact 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 place where seismic waves are generated is called the source. The vertical projection of the source on the ground is called the epicenter. The depth from the epicenter to the source is called the focal depth. Generally, the focal depth less than 70km is called shallow earthquakes, the depth of 70-300km is called Zhongyuan earthquake, and the depth greater than 300km is called deep earthquake. Destructive earthquakes usually occur in shallow earthquakes. For example, the focal depth of the Tangshan earthquake in 1976 was 12km.

Thermal convection of mantle materials. It is driven by the energy generated by the decay of radioactive elements in the earth. It is the external expression of energy release inside the earth. The internal energy release mainly takes the following forms: earthquake, volcano, plate movement and geological structure. The earthquake is one of them.

[1] There is a seismic source in the earth, which releases energy (seismic wave) to the outside world, thus causing vibration in a certain range;

(2) Other geological disasters or natural disasters can also indirectly induce earthquakes.

Thermal convection of mantle materials. It is driven by the energy generated by the decay of radioactive elements in the earth. It is the external expression of energy release inside the earth. The internal energy release mainly takes the following forms: earthquake, volcano, plate movement and geological structure. The earthquake is one of them.

Surface processes such as precipitation, wind, ocean currents and rivers are all driven by the external energy of the earth, namely the sun.