What will happen in an earthquake?

Under the action of in-situ stress, a series of physical, chemical, biological, meteorological and other abnormal changes in the source and nearby materials will be caused in the process of stress and strain gradually accumulating and strengthening. We call these abnormal changes related to earthquake preparation and occurrence as earthquake precursors (also called earthquake anomalies). It includes two categories: microscopic earthquake anomalies and macroscopic earthquake anomalies. (1) The macroscopic earthquake anomalies that can be directly perceived by human senses are called macroscopic earthquake anomalies. The macroscopic anomalies of earthquakes are diverse and complicated. There are hundreds of anomalies and thousands of anomalies. Generally, it can be divided into: groundwater anomaly, biological anomaly, geoacoustic anomaly, geolight anomaly, electromagnetic anomaly, meteorological anomaly, etc. 1. Groundwater anomalies include well water and spring water. The main anomalies are turbidity, bubbling, flowering, temperature rise, discoloration, off-flavor, sudden rise, sudden drop, borehole deformation, sudden exhaustion or gushing of springs, etc. People concluded before the earthquake. The sky is dry, the water level rises and falls, and the bloom flowers fall. Some change color, some change taste. 2. Biological abnormality. Some organs of many animals are particularly sensitive. They can know some disasters ahead of humans, such as jellyfish in the ocean can predict storms, mice can avoid mine collapse or harmful gases in advance. As for vision, hearing, touch, vibration and sense of balance, which organ plays the main role and which plays the role of auxiliary judgment may be different for different animals. Physical and chemical changes (vibration, electricity, magnetism, meteorology, abnormal radon content in water, etc.). ) The accompanying earthquake can often stimulate some sensory organs of some animals to produce abnormal reactions. For example, if the gravity of an area changes, some animals may be able to feel it through their balance organs; Abnormal vibration that may be detected by the auditory organs of some animals. Before the earthquake, the underground rock strata have been moving slowly day by day, showing a state of peristalsis, and there is strong friction between fault planes, so some people think that low-frequency sound waves will be generated on the friction fault planes only a few to ten times per second, which is lower than human hearing. People have to feel it at a speed of more than 20 times per second. On the other hand, animals are not. Animals that are very sensitive will be terrified as soon as they feel this sound wave, resulting in abnormal phenomena such as snakes coming out of holes, fish coming out of water, pigs and cows jumping around, dogs crying and wolves growling in winter. There are many kinds of animal anomalies, including large livestock, poultry, cave animals, hibernating animals, fish and so on. People also have a few words to summarize the abnormal situation of animals: before the earthquake, animals had omens. Pigs don't eat dogs and bite people. Ducks don't make noise on the shore, but chickens fly up the tree and scream loudly. In the ice and snow, the snake came out of the hole and the mouse ran with the mouse in its mouth. Rabbits bounce with their ears and fish bounce on the water. Bees move noisily, pigeons fly in horror and don't return to their nests. Every household quickly observes and reports the abnormal situation. In addition, some plants will have abnormal reactions before earthquakes. Such as germination, flowering, large-scale fruit withering and abnormal exuberance. 3. Meteorological anomalies People often describe earthquake prediction technicians as "managing the sky above, the ground below and the air in the middle", which really makes sense. Meteorological anomalies often occur before earthquakes, mainly including sweltering heat before earthquakes, people's anxiety and irritability, long drought or continuous rain, yellow fog and fog, dark sunshine and so on. Hail in June, etc. 4. Abnormal ground sound refers to the underground sound before the earthquake. Its sound is as varied as the thunder of a cannon, the running sound of a heavy car and the surging sound of a strong wind. When an earthquake occurs, longitudinal waves radiate from the source and spread along the ground, causing vibration and sound in the air. Because of the high speed but weak potential of longitudinal wave, people only smell its sound, but can't feel its movement. Therefore, shear waves are needed to move. According to records, the voice of the earth expands like boiling water in a cauldron. If a magnitude 3 earthquake is in the epicenter, you can often hear the voice of the earth. Ground sound is the result of the structural changes of underground rocks and the movement of liquid and gas contained in them, and a considerable part of it is a sign of impending earthquake. Mastering the knowledge of the earth's voice may have a better prediction and prevention effect on earthquakes. 5. Geophysical anomalies refer to the light emitted underground before the earthquake, with various colors. Its forms are also different, such as ribbon, sphere, column, dispersion and so on. Generally, ground light appears in a wide range, mostly within a few hours to a few minutes before the earthquake and lasts for a few seconds. China Haicheng, Longling, Tangshan, Songpan and other places have colorful luminous phenomena during and before the earthquake. Ground light is usually accompanied by natural phenomena, such as earthquakes, landslides, collapses, sand blasting and spraying. It is synchronous with other macro and micro anomalies, and its cause is always closely related to crustal movement. It is also controlled by geological conditions and the state of the surface and atmosphere, which can cause different degrees of harm to people, animals and plants. At present, all the reports of geomagnetic anomalies we have are about 1 minute a few seconds before the earthquake. For example, Haicheng earthquake, Lancang earthquake and Gengma earthquake all collected similar reports. 6. Also known as ground fog or ground fog, this fog is white, black, yellow and other colors, sometimes colorless, often appearing in a few days to a few minutes before the earthquake, often accompanied by strange smell, sometimes accompanied by sound or high temperature. 7. Abnormal ground motion refers to the ground shaking before the earthquake. It is a well-known phenomenon that the ground vibrates violently during an earthquake. However, before the earthquake, the ground sometimes shakes, and this kind of shaking is different from. Seismographs often can't record it, but many people can feel it. The most obvious ground motion anomaly occurred before1February 4, 1975 Haicheng earthquake with magnitude 7.3, and the time was from the end of February to the end of1October. An earthquake of magnitude 17 occurred in Dandong, Kuandian, Fengcheng, Shenyang and Xiuyan. 8. Abnormal ground heave refers to the uplift on the ground before the earthquake. 1973 About half a year before the magnitude 7.9 earthquake in Luhuo, Sichuan, a ground drum appeared on a lawn in Tuoba District, Ganzi County, shaped like an inverted iron pot and 20 meters high. Until the earthquake, there were ground fissures and ground subsidence. 9. Electromagnetic anomalies Electromagnetic anomalies refer to the anomalies of household appliances such as radios, televisions and fluorescent lamps before the earthquake. The most common electromagnetic anomaly is radio failure, and fluorescent lamps were also common in northern areas before the earthquake. 1a few days before the Tangshan earthquake of magnitude 7.8 on July 28, 976, many radios in Tangshan and its adjacent areas failed, and the sound was loud and small. Sometimes the frequency modulation is not accurate, and sometimes the noise appears continuously. Also before the Tangshan earthquake, some people in the city saw fluorescent lamps turn red at night and then turn them on. Some people in Beijing turn off the fluorescent lamp before going to bed, but the light is still on. Electromagnetic anomalies also include abnormal operation of some electrical equipment, such as abnormal microwave station, interference of wireless power plant, electronic alarm clock failure and so on. Macroscopic anomalies of earthquakes play an important role in earthquake prediction, especially in short-term and imminent prediction. Before Liaoning 1975 Haicheng earthquake with M = 7.3 and 1976 Songpan and Pingwu earthquakes with M = 7.2, seismologists and the masses had observed a large number of macroscopic anomalies, which provided important information for the successful prediction of these two earthquakes. However, we should also see that the macro phenomena listed above may be caused by various reasons. This is not necessarily a sign of an earthquake. For example, the fluctuation of well water and spring water may be related to rainfall, and may also be affected by nearby pumping, drainage and construction. The discoloration of well water may be caused by pollution, and the abnormal behavior of animals may be related to weather changes, diseases, estrus and external stimuli. Also be careful not to mistake welding arc light and lightning for earth light, and thunder for earth sound. Don't treat fireworks and flares as underground fireballs. Once you find an abnormal natural phenomenon, don't easily draw the conclusion that an earthquake is about to happen, let alone panic. Instead, it is necessary to find out the time, place and relevant situation of abnormal phenomena, protect the site, report to the government or the earthquake department, and let the professionals in the earthquake department investigate and verify to find out the truth. (2) The microscopic anomalies of earthquakes are imperceptible to human senses. Earthquake anomalies that can only be measured with special instruments are called microscopic anomalies of earthquakes, which mainly include the following categories: abnormal seismic activity: there is a certain relationship between large and small earthquakes. Although there are not many major earthquakes, there are many small and medium-sized earthquakes. Studying the characteristics of small and medium-sized earthquakes may help people predict the occurrence of future major earthquakes. Abnormal topographic deformation: Before the earthquake, the crust near the epicenter may undergo small deformation. Some rocks on both sides of the fault may shift slightly. With the help of precision instruments, this very weak change can be detected. Analyzing these data can help people predict the occurrence of major earthquakes in the future. Geophysical changes: In the process of earthquake preparation, some changes may occur in the physical properties of rocks in the source area and its surroundings. Measure the changes of gravity, geoelectricity and geomagnetism in different areas with precision instruments. It can also help people predict earthquakes. Changes of underground fluids: Groundwater (well water, spring water, water contained in underground rock formations), oil and natural gas and some other gases may be generated and stored in underground rock formations. These are underground fluids. Measuring the chemical composition and some physical quantities of underground fluid with instruments and studying their changes can help people predict earthquakes.