Handbook of earthquake popular science knowledge

Earthquake is a natural phenomenon. There are more than 5 million earthquakes on the earth every year, of which only about 50 thousand can be felt. Not all earthquakes will cause damage. Why did an earthquake happen? What are the types of earthquakes? How should we face the earthquake? Let me give you a brief introduction. Part 1 Basic knowledge of earthquakes Why did earthquakes happen? Earthquakes are the result of the movement of the earth. During the earth's movement, the earth's crust is constantly moving and changing. The movement and change of the earth gradually accumulated huge energy, which exerted a very strong force on the underground rocks. When rocks can't bear this force, they will suddenly break and move. Earthquake refers to the surface vibration caused by the energy released by the dislocation and fracture of rock mass in the crust. Rock fracture produces seismic waves, which propagate to the surface and the ground vibrates. This is an earthquake. What kind of earthquake will happen? There are three main types of natural earthquakes: volcanic earthquakes, subsidence earthquakes and tectonic earthquakes. Volcanic earthquake is the ground vibration caused by volcanic eruption, which makes magma impact the surface. Volcanic earthquakes have a relatively small influence range and cause relatively little damage. Collapse earthquake is the ground vibration caused by stratum collapse. For example, the collapse of underground limestone caves or the collapse of mined-out areas will cause small-scale ground vibration. This kind of earthquake generally has little loss. What we usually call an earthquake is called a tectonic earthquake. Tectonic earthquakes are caused by the dislocation and rupture of rock strata deep underground. This kind of earthquake accounts for more than 90% of the global earthquakes, and its vibration intensity is large, its influence range is wide, and it poses the greatest threat to mankind. Earthquakes are different in size. The magnitude of an earthquake is expressed by magnitude, and the stronger the earthquake, the greater the magnitude. Earthquakes can be divided into the following categories according to magnitude: earthquake magnitude is divided into weak earthquakes, felt earthquakes, destructive earthquakes and severely destructive earthquakes. Weak earthquake: generally refers to the earthquake below magnitude 3, which is usually not felt by people and can only be recorded by instruments. Sensible earthquake: generally speaking, it refers to an earthquake with magnitude above 3 and below 5. People can feel this kind of earthquake, but generally it won't cause damage. There are about 50,000 earthquakes of magnitude 3 or above every year in the world. Destructive earthquake: generally speaking, it refers to an earthquake of magnitude 5 or above, which can cause damage to the surface and its building facilities. On average, there are about 1000 earthquakes of magnitude 5 or above every year in the world. Severe destructive earthquake: refers to an earthquake of magnitude 7 or above. There are 10 to 20 such earthquakes every year in the world, but most of them occur in oceans and barren places. Every time the magnitude difference is more than 30 times, that is to say, an earthquake of magnitude 7 is equivalent to the capacity generated by nearly 1000 earthquakes of magnitude 5. When an earthquake occurs, it will produce seismic waves, and the vibration people feel is caused by the propagation of seismic waves. When an earthquake happens, you often feel it jumping up and down first, and then shaking from side to side. This is caused by the characteristics of seismic waves. Seismic waves are mainly composed of longitudinal waves and shear waves. P-wave travels very fast, but it is very weak, which makes people feel bumpy. The propagation speed of shear wave is a little slow, but it is relatively strong, which can cause huge shaking and cause serious damage to buildings on the surface. The degree of earthquake damage is not only related to magnitude, but also related to focal depth, epicentral distance, seismic wave propagation and other factors. We use intensity to measure the degree of earthquake damage. Generally speaking, after the earthquake, the damage in the epicenter area is the most serious and the intensity is the highest. From the epicenter to the surrounding areas, the intensity gradually decreased. An earthquake has only one magnitude, but it can be divided into different intensity zones. When an earthquake occurs, the place where the earthquake occurs inside the earth is called the source. The point on the ground facing the earthquake source is called the epicenter. The distance from the source to the epicenter is called the focal depth. The distance from any point on the ground to the epicenter is called epicentral distance. The distribution of earthquakes on the earth is uneven. It can be seen from the world epicentre distribution map that the global earthquake distribution is regular, mainly distributed in the Pacific Rim seismic belt, Eurasian seismic belt and Hailing seismic belt. China is located in the southeast of Eurasia, bordering the Pacific Ocean in the east, and is a country with severe earthquake disasters. According to the distribution map of major seismic zones in China, earthquakes are widely distributed in China, and there are about 20 major seismic zones in China. Part II Macroscopic Precursors of Earthquakes The phenomena related to earthquake preparation that occurred in nature before earthquakes are called earthquake precursors. There are microscopic anomalies and macroscopic anomalies in earthquake precursor anomalies. Microscopic anomalies, such as topographic changes and magnetotelluric anomalies, are mainly detected by high-precision scientific instruments. Macroscopic anomalies refer to the anomalies that people can feel with their senses, including groundwater anomalies, animal and plant anomalies, ground sound and ground light anomalies. In dry season, well water changes, well water bursts, abnormal ups and downs, no rain turns turbid, color changes, odor changes, air blows, flowers turn bubbles. This is a macroscopic precursor phenomenon of well water in groundwater. When the local water bubbles, becomes turbid and smells, it may be an abnormal reflection before the earthquake. Of course, many reasons will cause groundwater anomalies, and groundwater may also be affected by other environments. Second, animal anomalies Before many major earthquakes in history, many animals showed "abnormal behavior" to varying degrees. Therefore, people call animals "living instruments" for observing earthquake precursors. The common people write these abnormal phenomena as proverbs: Mules, horses, cows and donkeys don't enter the circle, escape from the reins, pigs don't eat and dogs don't bark, rabbits jump up and down, ducks can't climb trees, pigeons are so scared that they fly back to their nests to hibernate, snakes come out early, mice run around in droves, fish float on the water and move away in droves, and there are many factors that cause abnormal animal behavior, so abnormal animal behavior is not necessarily a precursor of an earthquake. 3. Ground light and ground sound Ground light refers to the phenomenon that the sky glows when people see an earthquake. There are other colors besides blue and white. Under normal circumstances, small earthquakes are not easy to cause terrestrial light, and the arrival of terrestrial light often indicates that a major earthquake is about to happen. Before Haicheng 1975 earthquake in Liaoning and Tangshan 1976 earthquake in Hebei, the phenomenon of terrestrial light was very prominent. If some earthquake-proof measures can be taken quickly and decisively at this time, it is possible to avoid earthquake disasters. Minutes and hours before an earthquake, there is often a sound coming from deep underground, which is called "earth sound". According to the survey, 95% of the residents who didn't sleep before the Tangshan earthquake heard the voice of the earth. These ground sounds are low, high and low, which is completely different from the usual city noise. The third part identifies and eliminates earthquake rumors. Because the earthquake is catastrophic, it is easy to panic about the earthquake. At this time, earthquake rumors appeared and spread quickly. Earthquake rumors are very harmful, which may not only disrupt our study, production and life, but also disrupt social stability and order. How to identify earthquake rumors? Rumors often have the following characteristics: 1, the "predicted" earthquake magnitude is very large, and the time and earthquake are very specific. For example, an earthquake will occur in "a certain city" and "a few days". It is said that a foreigner, an expert or an earthquake agency made a prediction. 3. Predictions with feudal superstitions or bizarre legends. There is a market for earthquake rumors because earthquake prediction is a worldwide scientific problem, and it is still in the exploration stage. China's earthquake prediction is at the leading level in the world, and it has successfully predicted earthquakes such as Haicheng in Liaoning. But at present, we can only predict some types of earthquakes to a certain extent, but not all earthquakes. Especially the imminent earthquake prediction is far less accurate than the weather forecast. The authority to issue earthquake prediction in China lies with the government, and no other unit or individual has the right to issue earthquake prediction news. Article 16 of the People's Republic of China (PRC) Earthquake Prevention and Disaster Mitigation Law stipulates that the state shall implement a unified release system for earthquake prediction. Therefore, there are thousands of earthquake news, remember the most basic one; Earthquake prediction news, only listen to the government. When dealing with earthquake rumors, we should "don't believe them, don't spread them, and report them in time". Part IV What should I do when an earthquake comes? As we all know, earthquakes are natural phenomena and objective laws, just like wind, rain and lightning. With the progress of science and technology, people's methods to prevent and deal with earthquake disasters are also increasing. What should we do in case of an earthquake? First of all, don't panic and act blindly. Judging whether the earthquake is big or small, near or far according to the feeling. Generally, a near earthquake jerks up and down first, and then shakes left and right, while a far earthquake just shakes back and forth. If it is a small earthquake or a distant earthquake, the houses we live in now are basically earthquake-resistant, so there is no need to panic. Secondly, we should take correct measures to avoid earthquakes. In different places, the methods of shock absorption are different. Let's talk about how to prevent earthquakes in schools, homes and public places. How to avoid shock in school: safety tips: 1, and all actions should follow the teacher's instructions; 2. Students should take care of each other, and Datong University should take care of young students; 3, shock absorption under the desk, orderly evacuation, do not crowd. Suppose we were having a class in the classroom when an earthquake suddenly happened. What should we do? First of all, we should squat or sit down, hide our heads under the desk and beside the platform, and never run around. Try to curl up and lower your center of gravity. Grab a solid object, such as a table leg. Protect your head and neck, eyes, and cover your mouth and nose. After the earthquake stops, evacuate in an orderly manner under the command of the teacher immediately. When evacuating, put the schoolbag on your head and keep a certain distance between the students before and after. Especially in cramped places such as classroom doors and stairwells, students who fall must slow down and help each other, and inform the students behind them in time to avoid crowding. After running outdoors, you must try to hide in an open place, around and without falling objects on your head. If we are in the playground or outdoors, we can stay where we are, cover our heads with our hands, and pay attention to avoid tall buildings or dangerous things. Never go back to the classroom because you forgot something. How to prevent electric shock at home: safety tip: 1, hide before running, don't run first; 2, hiding in a solid place (under the bed, in a small room, with support; 3. Open the door first and turn off the gas, power supply, etc. If you have time. In case of earthquake prevention, you should take refuge nearby according to the location during the earthquake, and then evacuate to a safe place after the vibration stops. You should hide under or beside a table, bed and other solid objects that can cover your body, or you can run to a small supported room such as kitchen and bathroom. If in time, open the door first to ensure the smooth passage; Turn off the gas switch and switch. When absorbing vibration, climb down, keep your body center of gravity lowest, face down, don't hold down your nose and mouth, and grab solid objects around you. You can also squat or sit down and curl up as much as possible. Pay attention to protect the head and neck, protect the head and back neck with your hands, if possible, put things around your head and close your eyes to prevent foreign objects from hurting you. Third, how to prevent electric shock in public places: safety tips: 1, obey the command of the staff 2, do not rush to the exit, keep a distance from the people in front; 3. If it is crowded, unbutton the collar button and cross your chest with your hands to protect your chest. After the earthquake, if there is an emergency shelter nearby, you should be led by an adult to get to the shelter. Earthquake emergency shelters generally rely on parks, green spaces, playgrounds and squares, and have the basic functions of emergency response. For example, emergency command, emergency materials distribution, emergency shelters, emergency toilets, etc. After the earthquake, we should also pay attention to the following problems: don't rush to the stairs, which will easily cause congestion. Don't turn on the light casually, because there may be flammable and explosive gases in the air. Don't make a phone call in a hurry, so as not to block the line and affect the disaster relief command and communication. Part V: Earthquake self-help and mutual rescue When disasters come, we should not only master the basic knowledge of disasters, but also know the basic skills of self-help and the basic measures of self-help and mutual rescue. According to statistics, during the Tangshan earthquake, 570,000 people were buried, and about 450,000 people escaped from danger through self-help and mutual rescue. Generally speaking, the survival rate of buried people rescued within half an hour after a major earthquake is 99%, which shows that self-rescue is one of the main measures to reduce casualties. First, a brief understanding of self-help and mutual rescue: First, self-help: the buried personnel (1) need to have a firm will to survive and eliminate fear. (2) When you can't get out of danger, you should try to free your hands and feet, cover your mouth and nose, and prevent the smoke from choking. (3) Keep a clear head, don't shout for help, don't hit objects with stones or iron, keep in touch with the outside world and save your strength. In the Tangshan earthquake, many children were buried, but with their wisdom and tenacious will, they persisted, avoided danger and saved lives. Second, the main methods of mutual rescue are: the buried personnel should maintain support to prevent further collapse injury; Expose the injured person's head first, remove foreign bodies in his mouth and nose, and keep breathing smooth. If he suffocates, give him artificial respiration immediately; When the oppressed can't climb out by themselves, don't pull and pull, so as not to cause further harm; For people with spinal injuries, door panels or hard stretchers should be used for handling; When you find a survivor who can't be rescued at the moment, you should mark the rescue.