Why are wind and rain forecasted in advance, but earthquakes are reported after the earthquake?

Because wind and rain can be predicted through meteorological cloud images, atmospheric humidity, temperature and other data, earthquakes cannot be predicted. Generally, only the time difference in the propagation rate of seismic waves of different properties can be used to provide early warning and remind people to do what they do. Be prepared.

Meteorological changes have obvious characteristics. In ancient times without modern science, people also summarized special meteorological phenomena such as cumulonimbus clouds. Cumulonimbus clouds are thick and rapidly rising clouds. During the process, the temperature drops and water vapor condenses to form dark clouds. The small water droplets in the dark clouds continue to develop and break through the updraft, and fall to the ground to form rainfall.

Modern times can use satellites to learn the direction, height changes, coverage area, etc. of clouds. This allows us to know where precipitation may occur. In addition, wind data and temperature data obtained by high-altitude detection balloons on the ground and other equipment temperature data measured by the box, etc., and then use a mathematical model to calculate the probability of precipitation in a certain place. Therefore, weather can be forecast in modern times. my country’s most advanced meteorological satellites can refresh cloud data every 15 minutes, and the country’s top meteorological team can already predict the probability of precipitation in as short as 5 minutes and formulate detailed plans for open-air sports events. It can carry out and broadcast plans and adjust many plans in a timely manner. It has high application value in many fields such as agriculture and industry.

Earthquakes are different. The places where earthquakes occur are usually several kilometers or tens of kilometers underground and cannot be seen. Humans do not have the corresponding instruments to monitor the movement of underground active faults in real time, and active faults The rupture reconstruction is an earthquake, which also makes earthquakes unpredictable. At present, we can only predict which places are almost certain to have earthquakes in the future based on historical data and long-term plate conditions, but it cannot be as accurate as weather forecasts within hours and minutes. .

But the propagation of earthquakes takes time, and earthquakes have longitudinal waves, transverse waves and surface waves. The longitudinal waves are propulsive waves. The propagation speed in the earth's crust is 5.5~7 kilometers/second. They reach the epicenter first, and then It is called P wave. The other two waves cause great damage to the ground, but propagate slightly slowly. Therefore, longitudinal waves can be used to warn earthquakes. However, it is necessary to set up a large number of seismic wave monitoring instruments in places where earthquakes often occur. When longitudinal waves are collected, they can be quickly When early warning information is sent out, there is a certain time difference before the arrival of transverse waves and surface waves. Even if it is only ten seconds, many people can be prepared to either escape to an open place or find a strong corner in a house to hide.

Human beings have used many methods to predict earthquakes, but except for a few accidental successes, most of them have failed. However, earthquake early warning is relatively easy to do, so there are now related APPs developed that can It runs in the background and sends early warning information to your mobile phone as soon as possible. Although the advance time is relatively small compared to transverse waves and surface waves, it can play a great role.