1, shallow earthquakes: earthquakes with focal depth less than 60km, and most destructive earthquakes are shallow earthquakes.

2. Zhongyuan earthquake: the focal depth is 60-300 kilometers.

3. Deep earthquake: an earthquake with a focal depth of more than 300 kilometers. Up to now, the focal depth of the deepest earthquake recorded in the world is 786 kilometers.

Second, according to the magnitude of classification

1, weak earthquake: earthquake with magnitude less than 3.

2. Sensible earthquake: an earthquake with magnitude equal to or greater than 3 and less than or equal to 4.5.

3. Moderate strong earthquake: an earthquake with magnitude greater than 4.5 and less than 6.

4. Strong earthquakes: earthquakes with magnitude equal to or greater than 6, among which those with magnitude greater than or equal to 8 are called huge earthquakes.

Extended data:

First, the mode of transmission

Seismic waves propagating inside the earth are called body waves, which are divided into longitudinal waves and shear waves.

The wave whose vibration direction is consistent with the propagation direction is longitudinal wave (P wave). Longitudinal waves from underground cause the ground to bump up and down.

The wave whose vibration direction is perpendicular to the propagation direction is shear wave (S wave). Shear waves from underground can cause the ground to shake horizontally. Because the propagation speed of longitudinal waves in the earth is faster than that of shear waves, in an earthquake, longitudinal waves always reach the surface first, while shear waves always lag behind.

In this way, when a large recent earthquake occurs, people generally feel up and down at first, and it takes several seconds to ten seconds before they feel a strong horizontal shaking. Shear wave is the main cause of damage.

Second, the earthquake magnitude

Magnitude is a measure of the magnitude of an earthquake, which is divided according to the amount of energy released by the earthquake and expressed by "magnitude". The scale of magnitude was first put forward by American seismologist C.F.Richter in 1935 when he studied the local earthquakes in California.

It is stipulated that the common logarithm of the horizontal maximum amplitude (single amplitude, in μm) recorded by "standard seismograph" (or "Anderson seismograph", with a period of 0.8s, a magnification of 2,800 and a damping coefficient of 0.8) at the epicentral distance 100km is the magnitude of the earthquake. Later, the records developed into remote stations and non-standard seismographs can also be used to determine the magnitude after conversion.

Magnitude can be divided into different categories, such as surface wave magnitude (MS), body wave magnitude (Mb) and near earthquake magnitude (ML), and can also be converted to each other. According to Richter's calculation method, the largest earthquake known by 2000 did not exceed 8.9.

The smallest earthquake has been measured to -3 with a high-magnification microseismic instrument. According to the magnitude, it can be divided into micro-earthquakes, micro-earthquakes, weak earthquakes (or small earthquakes), strong earthquakes (or moderate earthquakes) and large earthquakes.

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