The various signs that appear in nature before the earthquake may be related to the gestation and occurrence of the earthquake are called earthquake precursors. There are roughly two categories:
Micro-precursor: The pre-earthquake changes that are not easily detectable by human senses and can only be measured with instruments. For example, the deformation of the ground, the change of the earth's magnetic field and gravity field, the change of the chemical composition of groundwater, the activity of small earthquakes, etc.
Macro precursors: Precursors of an earthquake detected by human senses. Most of them appear near the earthquake. Such as the rise and fall of well water, muddy, abnormal animal behavior, ground sound, ground light, etc.
①Abnormal changes in water level and volume. ② Changes in water quality. Such as well water, spring water, etc. change color, change taste (such as becoming bitter, sweet), become muddy, have peculiar smell, etc.
③The change of water temperature. The water temperature exceeds the normal range of change.
④Others. Such as bubbling when turning flowers, sounding of jets, deformation of shaft walls, etc.
Animals are "living instruments" for observing the precursors of earthquakes. They often exhibit various abnormal behaviors before earthquakes and signal to people that disasters are approaching. Hundreds of animals have been found to have certain abnormalities before the earthquake. Among them, there are more than 20 kinds of abnormal reactions. The most common animal abnormalities are:
Frightening reactions: such as large livestock not entering the pen, dogs barking, birds or insects flying by surprise, abnormal group migration, etc.
Inhibitory abnormalities: such as slow behavior, or dullness, or being at a loss; or refusing to eat.
Life habits change: For example, hibernating snakes come out of holes, rats are not afraid of people during daytime activities, and a large number of frogs go ashore.
ElectromagneticThe anomaly refers to household appliances before the earthquake , Such as malfunctions of radios, televisions, fluorescent lamps, etc. The most common phenomenon is the malfunction of the radio, the weakening or disappearing of the mobile phone signal, and the malfunction of the electronic alarm clock.
Before the earthquake, there are often noises coming from deep underground. This is the "earth sound". The ground sounds generally appear a few minutes, hours, days or earlier before the earthquake; the most are the few minutes before the earthquake.
The sound of the ground sound is different and diverse from the familiar sounds of ordinary people.
Ground light is also a macroscopic phenomenon before the earthquake. China has observed it before many earthquakes, and they generally appear before or before the earthquake. Sometimes, it also appeared a few hours before the earthquake or earlier.
There are many colors of ground light, including red, yellow, blue, white, purple, etc., and some are like electric firelight. They have different shapes, including ribbon light, flake light, spherical light, cylindrical light, fire-like light and so on. The appearance of ground light is generally very short, so it is not easy to observe. It is also difficult to identify ground light, because its shape and color are sometimes similar to electric welding light and lightning.