Earthquakes are divided into natural earthquakes and artificial earthquakes. Natural earthquakes are mainly tectonic earthquakes, which are caused by the fracture and dislocation of rocks in the deep underground, so that the long-term accumulated energy is suddenly released and spread outward in the form of seismic waves, causing house shaking and ground vibration. Tectonic earthquakes account for more than 90% of the total number of earthquakes. Followed by earthquakes caused by volcanic eruptions, known as volcanic earthquakes, accounting for about 7% of the total number of earthquakes. In addition, earthquakes will also occur in some special circumstances, such as cave collapse (collapse earthquake) and large meteorites hitting the ground (meteorite impact earthquake).
Artificial earthquakes are earthquakes caused by human activities. Such as vibration caused by industrial blasting and underground nuclear explosion; High-pressure water injection in deep wells and water storage in large reservoirs increase the pressure on the earth's crust and sometimes induce earthquakes. (
1. What is the internal structure of the earth?
The interior of the earth can be divided into three layers: crust, mantle and core.
2. What is an earthquake?
A: The sudden release of slowly accumulated energy in the earth or the vibration of the earth's surface caused by human factors are called earthquakes.
3. What is a seismic source?
A place in the earth where earthquakes occur.
4. What is the epicenter? What is epicentral distance?
A: The projection point of the source on the ground is called the epicenter. The distance from the epicenter to any point on the ground is called epicentral distance.
5. What is the focal depth? What are shallow earthquakes, deep earthquakes and moderate earthquakes?
A: The vertical distance from the epicenter to the source is called the focal depth.
The focal depth of shallow earthquakes is less than 70km, the focal depth of deep earthquakes is more than 300km, and those with focal depth of 70-300km are moderate earthquakes.
6. How deep is the earthquake with the deepest focal depth in the world? Where are many deep earthquakes?
A: The earthquake east of Sulawesi, Indonesia1June 9, 934, with a focal depth of 720 kilometers.
Deep-focus earthquakes are most common in deep trenches around the Pacific Ocean, with deep-focus earthquakes in the northeast of China and moderate-deep earthquakes in the waters east of Taiwan Province Province.
7. According to the causes of earthquakes, they can be divided into several types.
Natural earthquakes and artificial earthquakes.
Natural earthquakes include tectonic earthquakes, volcanic earthquakes and collapse earthquakes. Artificial earthquakes include vibrations caused by underground nuclear explosions and earthquakes caused by reservoir impoundment.
8. What is a tectonic earthquake? What are the characteristics?
Tectonic earthquake is a natural earthquake caused by rock fracture caused by tectonic movement in the earth, which is closely related to geological tectonic system and mostly distributed in the crust 5-30 kilometers underground. It is characterized by long duration, wide range of influence, strong destructive power and repetitiveness. Tectonic earthquakes account for more than 90% of global earthquakes.
9. What is a volcanic earthquake?
The natural earthquake caused by volcanic eruption has a short duration, a small influence range and a focal depth of less than 10 km.
10. What is a collapse earthquake?
The top of the underground cave formed by natural causes can't support the earthquake caused by rock collapse.
1 1. What are near earthquakes, near earthquakes and far earthquakes?
The epicentral distance is less than 100 km, which is a local earthquake; The epicentral distance1000 km-1000 km is a near earthquake; The epicentral distance is greater than 1000 km, which is a teleseism.
12. The magnitude is the scale. What are sensible earthquakes, destructive earthquakes, major earthquakes and minor earthquakes?
Small earthquakes with magnitude less than 3, sensible earthquakes with magnitude above 3, destructive earthquakes with magnitude above 5, and large earthquakes with magnitude above 7.
What is the order of magnitude?
Magnitude refers to the magnitude of the earthquake itself, which is related to the energy released by the source. The greater the energy, the greater the magnitude, and the earthquake has only one magnitude. The magnitude difference is one level and the energy difference is 33 times.
What is the earthquake intensity? What are the factors that affect the earthquake intensity?
The degree of influence and destruction of an earthquake on a certain area is called intensity. Generally speaking, the greater the magnitude, the greater the intensity. The epicentral distance of the same earthquake is different with different intensities. Besides magnitude and epicentral distance, the factors that affect intensity are also related to address structure and seismic performance of ground buildings.
15. What is the criterion for judging each intensity indicated in the China Earthquake Intensity Table?
What is seismic wave?
Seismic wave is an elastic wave generated inside the earth when an earthquake occurs, and it is a way to release energy from an earthquake.
17. What kind of seismic waves? What are the characteristics?
Seismic waves include body waves and surface waves, and body waves are divided into longitudinal waves and shear waves.
The vibration direction of the shear wave is perpendicular to the advancing direction of the wave, while on the ground, the vibration direction of the longitudinal wave is consistent with the propagation direction, reflecting the vibration of the ground jumping up and down (jumping and lifting). Compared with the two, longitudinal waves travel faster than shear waves, so after an earthquake, you feel like jumping up and down, followed by shaking from side to side. In addition, the amplitude of shear wave is larger than that of longitudinal wave, which is destructive. The horizontal rocking force of shear wave is the main cause of building damage.
18. What's the difference between magnitude and intensity?
The magnitude reflects the magnitude of the earthquake itself, which is only related to the earthquake release ability, while the intensity reflects the impact and damage to the ground. An earthquake has only one magnitude, but its intensity varies from place to place. The intensity is not only related to the magnitude, but also to the focal depth, the distance from the epicenter and the conditions under which seismic waves pass through the medium.
19. How many earthquakes have occurred on the earth in a year, and how many destructive earthquakes are there?
There are more than 5 million earthquakes in the world every year, including destructive earthquakes 1000, and more than a dozen major earthquakes of magnitude 7 or above.
20. Where are there many earthquakes in the world?
Earthquakes in the world are mainly concentrated in the following two areas:
(1) Pacific Rim Seismic Belt: It includes the Pacific coast of North and South America, Aleutian Islands and kamchatka peninsula, passes through Thousand Islands and Japanese Islands, passes through Taiwan Province Province of China to the south, and then turns to the Philippines to reach New Zealand to the southeast.
(2) Himalayan-Mediterranean seismic belt: from western Indonesia through Myanmar to Hengduan Mountains and Himalayas in China, across Pamirs, and through Central Asia to the Mediterranean Sea and its coast.
2 1. How deep did the seismic belt originate?
The focal points of most earthquakes in the world are mostly distributed in areas 5-30 kilometers underground.
22. What is the biggest earthquake in the world?
At present, the largest earthquake recorded has not exceeded M = 8.9, namely, the M = 8.9 earthquake in Chile, South America on May 22nd 1906, 65438+1October 3rd1,the offshore near the Ecuador-Colombia border in South America, and the sea east of Japan's Sanlu on March 2nd 1933.
23. How many major earthquakes of magnitude 8 or above have occurred in China? Give three examples.
China is a country with many earthquakes. According to the existing statistics, there were 8+earthquakes 17 times, 1679, and an 8+earthquake occurred in Sanhe, Hebei Province in September. 1920 65438+an earthquake of magnitude 8.5 occurred in Haiyuan in February; 1927 An earthquake of magnitude 8 occurred in Gulang, Gansu Province in May; An earthquake of magnitude 8.5 occurred in Chayu, Tibet in August, 1950, 10, and an earthquake of magnitude 8.5 occurred in the sea area east of Taiwan Province Province in October, 1972.
24. There have been several earthquakes of magnitude 7 or above in our province, and four cases have been cited.
* * * happened five times. Sanhe 1679 M8 earthquake; 1830 an earthquake of magnitude 7.5 occurred in Cixian; 1966 Xingtai m 7.2 earthquake; 1976 Tangshan earthquake with magnitude 7.8; 1976 Luanxian 7. 1 earthquake.
25. What are the major earthquakes in China?
The main earthquakes in eastern China are Tanlu seismic belt, Hebei plain seismic belt, Wei Fen seismic belt, Yanshan Bohai seismic belt and southeast coastal seismic belt. There are North Tianshan seismic belt, South Tianshan seismic belt, Qilian seismic belt, Kunlun seismic belt and Himalayan seismic belt in the west. The central part is the North-South seismic belt, which runs through China. There is also the Taiwan Province seismic belt, which is a part of the western Pacific seismic belt.
26. What seismic zones are there in North China?
The earthquake zone is a strong earthquake zone with frequent earthquakes. Earthquakes in North China include Hebei Plain seismic belt, Wei Fen seismic belt, Yanshan-Bohai seismic belt and Lujiang seismic belt. According to geomechanics, China can be roughly divided into 20 seismic zones.
1. Taiwan Province province belt; 2. Coastal areas of Fujian and Guangdong; 3. Northeast deep seismic belt; 4. Yingkou-Tancheng-Lujiang belt; 5. Hebei plain belt; 6. Haiyuan-Songpan-Ya 'an Belt; 7. Shanxi belt; 8. Weihe Plain Belt; 9. Yinchuan Belt; 10. Lanzhou-Tianshui belt; 1 1. Hexi Corridor; 12. Mabian-Qiaojia-Copper Kelp; 13. Mianning-Xichang-Yufu Belt; 14. Tengchong-Lancang River belt; 15. Ailao mountain belt; 16. Luhuo-Ganning belt; 17. Huashixia belt; 18. Lhasa-chayu belt; 19. western Tibet; 20. Tianshan belt.
27. Who invented the first seismograph in the world? Brief introduction of seismograph development?
The first seismograph in the world was invented by China scientist Zhang Heng in BC 132. It is called the seismograph after the wind.
The modern seismograph was built in the 1990s of 18, and its principle is basically similar to that of the seismograph after the wind. Seismographs have developed rapidly, including long period and short period, and have realized wireless telemetry, magnetic tape recording and digitization. The sensitivity ranges from several times to several thousand times, tens of thousands of times, hundreds of thousands of times or even millions of times, and the period ranges from 0.05 second to 100 second.
28. What is earthquake prediction? How many kinds are there?
Earthquake prediction is the prediction of the time, place, magnitude and impact of destructive earthquakes in the future, which can be divided into long-term prediction, medium-term prediction, short-term prediction and imminent earthquake prediction.
29. What is the content of long-term earthquake prediction?
Long-term earthquake prediction refers to the prediction of earthquake risk and its influence in a few years to decades or longer. Including national or regional seismic zoning; Construction planning and project site seismic intensity, ground motion parameters, seismic zoning and earthquake damage prediction; National or regional seismic activity trend prediction.
30. What are the mid-term, short-term and impending earthquake predictions?
Medium-term earthquake prediction refers to the prediction of the time, place and magnitude of destructive earthquakes in several months to several years;
Short-term earthquake prediction refers to the prediction of the time, place and magnitude of destructive earthquakes in a few days to several months;
Impending earthquake prediction refers to the prediction or warning of a destructive earthquake in a few days;
3 1. How many earthquakes were successfully predicted in China?
Two earthquakes on March 23rd and 24th in Wuqia County, Xinjiang have been successfully predicted, 197 1. 1February 4, 975 Haicheng, Liaoning, earthquake with magnitude 7.3; 1Longling earthquake with M = 7.5 in Luxi, Yunnan on May 29th, 976,1Songpan earthquake with M = 7.3 in Sichuan on August 6th, 976. In particular, the Haicheng earthquake of magnitude 7.3 was recognized all over the world and won the second prize of national scientific and technological progress. On July 1995, an earthquake of magnitude 7.3 occurred in Menglian, Yunnan. On July 1 1, the Seismological Bureau of Yunnan Province reported to the local county cadre meeting and asked the local government to take measures, which greatly reduced the losses and was commended by the Yunnan Provincial Government and the State Seismological Bureau.
32. The laws and regulations on earthquake prediction in China were approved by leaders at which level, when was it approved, and when was it promulgated by the State Seismological Bureau?
1approved by the State Council on June 7th, 988,1released by the State Seismological Bureau on August 9th, 988.
33. What is the significance of China earthquake prediction laws and regulations?
In order to strengthen the management of earthquake prediction and ensure the safety of people's lives and property and the smooth progress of national economic construction.
35. Is there a precursor to the earthquake?
Yes Under the action of in-situ stress, in the process of stress and strain gradually accumulating and strengthening, rock mass will cause a series of abnormal changes in physics, chemistry, biology and meteorology of the source and nearby materials. We call these abnormal changes related to earthquake preparation and occurrence as earthquake precursors. Since Xingtai 1966 earthquake, China has recorded 1000 precursory anomalies before 70 moderate earthquakes.
36. What are the types of earthquake precursor anomalies?
It can be divided into 10 categories, namely: earthquake precursors, crustal deformation, gravity, geomagnetism, geoelectricity, hydrogeochemistry, dynamics of underground fluids (water vapor, gas and oil), stress, strain, meteorological anomalies and macroscopic precursor anomalies.
Types of earthquakes
As the saying goes, an earthquake is an earthquake. What caused the earthquake? In ancient times, people lacked understanding of the earth, thinking that the earth under people's feet was carried on their backs by big whales. When whales were tired, they wanted to turn over, causing the earth to shake. Others say that "the earth is angry" means "hugging people" and so on. Scientists tell us that earthquakes are just natural phenomena of sudden tremor of the earth's crust. Because of the different causes of crustal vibration, earthquakes can be divided into tectonic earthquakes, volcanic earthquakes and subsidence earthquakes.
Tectonic earthquake is an earthquake caused by rock fracture, dislocation movement and great changes in geological structure, so it is called tectonic earthquake, also known as fracture earthquake. Most earthquakes in China and the world belong to this kind of earthquake. The focal depth of a tectonic earthquake is usually within 60 kilometers. Earthquakes with a depth of about 70-300 kilometers are called moderate-deep earthquakes. Earthquakes with a depth of more than 300 kilometers to about 700 kilometers are called deep earthquakes. All deep-seated seismic areas usually coincide with the strike of the Pacific deep-sea trough far from the coastlines of South America and Asia. Scientists now believe that the trough is a sign of the position where several huge moving parts of the earth's crust collide and pile up with each other. After a period of stalemate, the rocks began to deform. When the deformation of rock strata exceeds its maximum limit, it will suddenly break and move, thus producing an earthquake. This view is more convincing.
Not long ago, a scientist at the California Institute of Stratigraphy suggested that the frequent strong wind force on the earth's surface may be one of the important driving forces for inducing earthquakes. 1September 1986 and1June 1987+00, several moderate earthquakes of magnitude 4.5 occurred in southern California. Before these earthquakes, the scientist monitored and recorded the wind changes in this area in detail. He found that 4-6 weeks before each earthquake, a series of unusually strong high pressure appeared in the earthquake area, which led to strong winds in the Pacific Ocean hundreds of miles near the California coast. He believes that these high pressures and strong winds caused the earthquake. However, this is just a family statement.
Earthquakes caused by volcanic eruptions are called volcanic earthquakes. This kind of earthquake coincides with volcanic eruption. It is the crustal vibration caused by the energy impact caused by volcanic eruption. Volcanic earthquakes are sometimes quite strong, such as those caused by volcanic eruption in caracalla, which stirred up waves as high as 30 meters and shattered the walls and windows of Jakarta 150 kilometers away. However, the area affected by this kind of earthquake is usually limited to tens of kilometers near the volcano, and the frequency of occurrence is less, accounting for only about 7% of the number of earthquakes, causing less harm.
Collapse earthquakes are usually caused by cave collapse. For example, in karst areas where limestone is developed, occasional cave collapses or large rocks fall, which may cause small earthquakes. Cave collapse will also occur after salt mounds and soft strata are eroded by groundwater. The number of such earthquakes is even smaller, accounting for only about 3% of the total number of earthquakes, with small magnitude, limited impact and small losses.
Sometimes, under man-made conditions, it may also cause a collapse earthquake. For example, after the underground ore body is mined, the surrounding rock loses its support, which often leads to collapse and earthquake. This kind of earthquake sometimes causes disastrous losses. This phenomenon often occurs in Canada, South Africa and other countries, especially in coal mines.
Earthquake is a terrible "natural disaster" in people's minds, and many people turn pale when they mention it. In fact, most earthquakes are so small that only sensitive instruments can detect them. Most earthquakes that people can feel occur in sparsely populated mountainous areas. China is a country with frequent earthquakes, and hundreds or even thousands of earthquakes occur every year. However, it takes decades or hundreds of years to encounter an earthquake as destructive as the Tangshan earthquake.
Earthquake is a natural phenomenon. It can be divided into several types according to the different causes.
Tectonic earthquake. It is caused by the in-situ stress produced in the hard strata of the crust and upper mantle in the year of crustal movement, which breaks or revives the original fault. The occurrence of tectonic earthquakes is often sudden, but its gestation process is very long. In the initial stage of in-situ stress, the rock stratum has a certain strength and will not break immediately. When the local stress increases and reaches a certain limit, the rock stratum breaks and an earthquake occurs. Tectonic earthquakes caused by faults or fault activities account for 90% of the total number of earthquakes in the world. Almost all of these strong earthquakes belong to this type, such as 1960 southern Chile earthquake with magnitude 8, 1966 Xingtai earthquake with magnitude 7.2, and 1976 Tangshan earthquake in China with magnitude 7.8. This kind of earthquake is very harmful to human beings.
Volcanic earthquake. Earthquakes caused by volcanic activity are called volcanic earthquakes. When hot magma gathers, expands and erupts in the crust before eruption, the huge impact force can cause rock fracture or fault dislocation, which will lead to earthquakes. Volcanic earthquakes have their own characteristics: the influence range is small, and they appear in the form of small earthquakes. 1000 small earthquakes occurred in succession within a few days after the eruption of Montsoufriere volcano in the Caribbean islands in August 1976. According to statistics, about 7% of earthquakes in the world belong to volcanic earthquakes.
Collapse earthquake. Collapse earthquakes often occur in areas where limestone and other soluble rocks are distributed. This is because the dissolved rocks have been eroded by groundwater for a long time, forming many caves, and the top of the caves collapsed, causing earthquakes. 198 1 1 In some areas of Nankou Township, Yulin County, Guangxi Province, people heard the underground rumbling, and soon there was a collapse earthquake. In a few days, more than 200 places collapsed and some houses and fields were destroyed. The collapse earthquake has little influence and harm, accounting for only about 3% of the total number of earthquakes.
Other earthquakes. Many human activities can also cause earthquakes. One is that human activities directly cause earthquakes, such as blasting, piling and the passing of heavy vehicles, which can make the ground vibrate. This kind of earthquake is called artificial earthquake. This kind of earthquake generally does not cause harm, but it has a great influence on those instruments and equipment that require high precision and stability. Therefore, when installing these instruments and equipment, we should try our best to eliminate the unfavorable factors of man-made earthquakes. There is also an earthquake caused or induced by human activities. For example, the huge impulse generated by underground nuclear tests can cause fault activity; Reservoirs can also cause earthquakes, because most reservoirs are built in canyons, and there are often faults underground. On the one hand, the reservoir impoundment increases the pressure of the crust there, and at the same time, water permeates into the fault zone, acting as a lubricant, reducing the friction between faults and making them easy to slide. 1962 The M6.4 earthquake that occurred shortly after the storage of Xinfengjiang Reservoir in Guangdong Province in March was one of the largest reservoir-induced earthquakes in the world.
No matter what kind of earthquake, there are certain rules to follow. Now that we know the causes of various earthquakes, we won't feel the mystery of earthquakes any more. Of course, because some earthquakes will do great harm to human beings, we must take them seriously.
Earthquake precursor
Under the action of in-situ stress, in the process of stress and strain gradually accumulating and strengthening, rock mass will cause a series of abnormal changes in physics, chemistry, biology and meteorology of the source and nearby materials. We call these abnormal changes related to earthquake preparation and occurrence as earthquake precursors (also called earthquake anomalies). It includes microscopic earthquake anomalies and macroscopic earthquake anomalies.
Macroscopic anomaly of (1) earthquake
Earthquake anomalies that can be directly perceived by human senses are called earthquake macroscopic anomalies. The manifestations of earthquake macro-anomalies are diverse and complex, with hundreds of kinds of anomalies and thousands of anomalies, which can be roughly divided into groundwater anomalies, biological anomalies, geoacoustic anomalies, geooptical anomalies, electromagnetic anomalies, meteorological anomalies and so on.
1, groundwater anomaly
Groundwater includes well water, spring water, etc. The main anomalies are turbidity, bubbling, flowering, temperature rise, discoloration, odor change, sudden rise, sudden drop, borehole deformation, sudden exhaustion or spewing of spring water, etc. People summed up the proverbs of well water changes before the earthquake:
Well water is a treasure, and earthquakes have precursors.
When it doesn't rain, the spring water is turbid, and when it dries, well water emerges.
The water level rises and falls, and flowers are bubbling.
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 disasters or harmful gases in advance, and so on. As for the organs of vision, hearing, touch, vibration and balance, which plays the main role and which plays the role of assisting 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 and cause abnormal reactions. If the gravity of an area changes, some animals may be able to feel it through its balance organs; Some animals' hearing organs may be able to detect abnormal vibrations. Before the earthquake, the underground strata have been moving slowly day by day, showing a creeping state, and there is strong friction between fault planes, so some people think that there will be low-frequency sound waves on the friction fault planes, only a few to ten times per second, which is lower than human hearing. People need more than 20 sound waves per second to feel it, but animals don't. Very sensitive animals will be frightened when they feel this sound wave, resulting in abnormal phenomena such as winter snakes coming out of holes, fish jumping out of the water, pigs and cows jumping in circles, dogs barking and wolves growling. There are many kinds of animal anomalies, including large livestock, poultry, cave animals, hibernating animals, fish and so on. The abnormal situation of animals, people also have a few words to sum up well:
Animals have signs before earthquakes, so it is very important to prevent and treat them by groups.
Cattle, sheep, mules and horses don't enter the stables, and pigs don't eat dogs and bite people.
Ducks don't go into the water and make noise on the shore, but chickens fly up the tree and scream loudly.
The snake came out of the hole in the ice and snow, and the mouse ran with the mouse in its mouth.
The rabbit jumped and bumped, and the fish jumped into the water.
Bees are moving noisily, but pigeons are too scared to fly back to their nests.
Every household observes and reports any abnormal situation.
In addition, some plants also had abnormal reactions before the earthquake, such as germination, flowering, fruiting or large-scale withering, abnormal exuberance and so on.
3. Meteorological anomalies
People often describe earthquake prediction scientists and technicians as "managing the sky, the ground and the hollow", which is indeed reasonable. Before the earthquake, the weather often appeared abnormal. There are mainly sultry before the earthquake, anxiety and irritability, long drought without rain or heavy rain, yellow fog, dark sunshine, strange wind, hail in June and so on.
4. Abnormal ground sound
Geosound anomaly refers to the sound emitted underground before the earthquake. Its sound is as changeable as cannon and thunder, like the driving of heavy vehicles and the surge of strong winds. When an earthquake occurs, longitudinal waves radiate from the source and propagate along the ground, making the air vibrate and sound. Because of the high speed but weak potential of longitudinal wave, people only smell its sound, but don't feel it unconsciously until the arrival of shear wave. Therefore, there is often a record in the epicenter that "before every earthquake, the underground sound expands like gas, like boiling water in a tripod". If you are in the epicenter, you can often hear the sound of a magnitude 3 earthquake. Geosound is the result of the structure and structure 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 geosound may have a good effect on earthquake prediction and prevention.
5, abnormal grounding light
Geophysical anomalies refer to the light emitted underground before the earthquake, which has various colors, such as silver blue, white purple, etc., which are rare in daily life, but mainly red and white; Its forms are also different, such as ribbon, sphere, column, diffusion and so on. Generally speaking, the earth's light appears in a wide range, mostly within a few hours to a few minutes before the earthquake and lasts for a few seconds. In China, colorful luminous phenomena appeared during and before the Haicheng, Longling, Tangshan and Songpan earthquakes. Terrestrial light is often accompanied by natural phenomena such as earthquakes, landslides, landslides, collapses, sand blasting, water spraying and air jetting, and often moves regularly along a fault zone or an area, and is synchronized with other macro and micro anomalies, and its causes are always closely related to crustal movement. And controlled by geological conditions and the state of the surface and atmosphere, it can cause different degrees of harm to people, animals and plants.
At present, all the geomagnetic anomaly reports we have are from a few seconds before the earthquake to 1 minute. Such as Haicheng earthquake, Lancang earthquake and Gengma earthquake, similar reports have been collected.
6. Abnormal ground gas
Geo-atmospheric anomaly refers to the fog generated underground before the earthquake, also known as geo-aerosol or geo-fog. This kind of fog, with white, black and yellow colors, sometimes colorless, often appears in the days to minutes before the earthquake, often accompanied by strange smell, sometimes accompanied by noise or high temperature.
7. Abnormal ground movement
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. But before the earthquake, sometimes I feel the ground shaking. This kind of shaking is different from an earthquake, and it swings very slowly. Seismographs often can't record it, but many people can feel it. The most obvious ground motion anomaly occurred before the Haicheng earthquake of magnitude 7.3 on February 4th, 1975. From the end of February to the end of June, there were 65438+ anomalies in Dandong, Kuandian, Fengcheng, Shenyang and Xiuyan.
8. Abnormal grounding drum
The ground uplift anomaly 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 drum appeared on a lawn in Tuoba District, Ganzi County. It was shaped like an inverted iron pot, about 20 cm high, and cracks appeared intermittently around it. The swelling disappeared after a few days, and it was repeated many times until the earthquake occurred.
Anomalies similar to ground heave include ground fissures and 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 before the North China earthquake. 1a few days before the Tangshan earthquake of magnitude 7.8 on July 28, 976, many radios in Tangshan and its surrounding areas broke down, with loud and small sounds, inaccurate frequency modulation and sometimes continuous noise. Also before the Tangshan earthquake, some people in the city saw fluorescent lamps turn red first and then light up at night. 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 motor equipment, such as abnormal microwave stations, interference from wireless power plants, and failure of electronic alarm clocks.
Macroscopic anomalies of earthquakes play an important role in earthquake prediction, especially in short-term and imminent prediction. Before the 1975 Haicheng M = 7.3 earthquake and the 1976 Songpan and Pingwu M = 7.2 earthquakes, seismologists and the general public had observed a large number of macroscopic anomalies, which provided important information for the successful prediction of these two earthquakes. However, it should also be noted that the above macro phenomena may be caused by various reasons, not all of which are signs of earthquakes. 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 and odor 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, thunder for earth sound, and fireworks and flares for 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) Microscopic anomalies of earthquakes
The seismic anomalies that can't be detected by human senses and can only be measured by 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. Study the characteristics of moderate and small earthquakes. It is possible to help people predict the occurrence of future major earthquakes.
Abnormal topographic changes: Before the earthquake, the crust near the epicenter may be slightly deformed, and the rocks on both sides of some faults may be slightly displaced. With the help of precision instruments, this very weak change can be detected, and analyzing these data can help people predict the occurrence of future major earthquakes.
Geophysical changes: In the process of earthquake preparation, some changes may occur in the physical properties of rocks around the source area. Using precision instruments to measure the changes of gravity, geoelectricity and geomagnetism in different areas 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 other gases may be generated and stored in underground rock formations, all of which are underground fluids. Using instruments to measure the chemical composition and some physical quantities of underground fluid and study their changes can help people predict earthquakes.