World earthquake science knowledge 10 questions

1. What is the depth of the source?

A: The distance from the source to the ground is called the depth of the source. Earthquakes with focal depths within 60 km are shallow-source ones. Earthquakes with depths of more than 300 km are deep-source ones. Earthquakes with source depths of 60-300 km are mid-source ones. For earthquakes of the same intensity, the shallower the source, the heavier the impact or damage caused. The vast majority of earthquakes in China are shallow earthquakes.

2. What is the periodicity of seismic activity?

A: Through the statistics of historical earthquakes and large amounts of data of current earthquakes, it is found that the distribution of seismicity in time is uneven: there are more earthquakes in a period of time, and the magnitude is larger, which is called the active period of earthquakes; Less, smaller magnitude, known as the quiet period of seismic activity; shows the periodicity of seismic activity. In each active period, there may be multiple earthquakes of magnitude 7 or more, and even magnitude 8 earthquakes. Seismic activity cycles can be divided into long periods of several hundred years and short periods of several decades; the activity periods of different seismic belts are not all the same.

3. What is the intensity of earthquakes and how does it differ from magnitude?

A: Seismic intensity is a “ruler” that measures the impact and damage of an earthquake. The intensity and magnitude are different. Magnitude reflects the size of the earthquake itself, which is only related to the amount of energy released by the earthquake. Intensity, on the other hand, reflects the consequences of the earthquake. After an earthquake, the intensity of the earthquake is different in different locations. For example, the magnitude is like a wattage of a light bulb. The intensity is like a certain point illuminated by light. It is not only related to the power of the bulb, but also related to the distance. Therefore, an earthquake has only one magnitude, and the intensity is different everywhere. In general, the intensity in the epicentral region is the highest, and the intensity gradually decreases as the epicenter distance increases. For example, the Tangshan earthquake in 1976 had a magnitude of 7.8 and an epicentral intensity of XI degrees. Affected by the Tangshan earthquake, the intensity of Tianjin was VIII degrees, and the intensity in most areas of Beijing was VI degrees. It was farther to Shijiazhuang and Taiyuan. Even lower.

4. What is the technical standard for assessing earthquake intensity in China?

A: The technical standard for assessing seismic intensity in China is "China Earthquake Intensity Scale (1980)", which classifies the intensity into 12 degrees. One of the criteria for its assessment is: I-V degrees are based on the feelings of people on the ground; VI- The degree of X is mainly based on house damage, and the person's feeling is for reference only; XI and XII are mainly caused by house destruction and surface destruction. According to the evaluation standard of this intensity table, generally speaking, people have feelings when the intensity is III-V degrees, there are destructions above the VI degree, the destruction of the IX-X degree is severe, and the XI degree or more is devastating.

5. Why is the epidemic after the earthquake easily popular?

Answer: After the strong earthquake occurred, the water source and water supply system in the disaster area were damaged or contaminated, and the living environment in the disaster area was seriously deteriorated, so it was very easy to cause epidemics. The pros and cons of social conditions and the epidemic after the disaster have become very popular. For example, on January 23, 1556, an earthquake of magnitude 8 occurred in Huaxian County, Shaanxi Province, China. Historical records showed that the death toll of “a famous person” reached 830,000; in reality, only tens of thousands of people died directly from the earthquake, and the remaining 70 counties. Ten thousand people died of plague and famine. In the new socialist China, the post-quake plague has been effectively controlled. For example, when the 7.8-magnitude Tangshan earthquake occurred in 1976, it was a hot summer. However, it created a miracle of “no major epidemic after the catastrophic disaster”, and the incidence of infectious diseases was lower in the following spring than in the normal years.

6. Can the earthquake forecast?

A: Earthquake forecasting is a world-recognized scientific problem. It is at an exploratory stage both at home and abroad. Research began from about the 1950s and 1960s. The comprehensive study of earthquake prediction in China started in the 1966 Xingtai earthquake in Hebei Province. After more than 40 years of efforts, some progress has been made. Some destructive earthquakes have been forecasted to varying degrees. However, practice has shown that the various phenomena that may be observed in connection with earthquakes present great uncertainties; the predictions made, especially short-term predictions, are mainly empirical. The current level and status quo of China's earthquake prediction are as follows: —— Some understanding of earthquake precursory phenomena, but it is far from the understanding of regularity; —— Under certain conditions, certain types of earthquakes can be forecasted to a certain degree; - There is a certain degree of understanding of medium and long-term forecasts, but the success rate of short-term impending predictions is still very low.

7. What is earthquake rumor?

A: Sometimes, there are some "messions" about earthquakes circulating in the society. They are not the government's publicly announced earthquake prediction opinions, but they are earthquake rumours. Strong earthquake disasters cause people's fear of earthquakes. Coupled with the lack of understanding of earthquake knowledge and relevant laws and regulations, people tend to listen to unfounded, so-called "earthquake news." This is the soil through which earthquakes can be heard.

The specific reasons for the occurrence of earthquake rumors include: Some natural phenomena, such as the phenomenon of the secondary blooming of fruit trees due to climate warming, the reclaiming and thawing of the spring earth, are mistaken for earthquake anomalies. 2 The suspicions caused by normal business activities in the earthquake sector, such as field observations, earthquake inspections, the implementation of certain 3 precursory anomalies, earthquake consultation, earthquake resistance conferences, and earthquake prevention and disaster reduction propaganda. 4 Demonstrating propaganda from overseas, or doing something with ulterior motives. Deluded by feudal superstitions.

8. How is the earthquake microscopic precursor observed?

A: Seismographs are used to observe small earthquakes; observations of other micro-precursors must use precursory observation instruments. For example, instruments for observing and recording crustal deformation include inclinometers, self-recording water meters, extensometers, level meters, laser distance meters, etc.; magnetometers, nuclear rotation meters, and geomagnetic theodolites that observe and record changes in the geomagnetic field. Observed ground electricity, ground stress, gravity, waterlogging, water level, water quality and other microscopic precursory phenomena also have corresponding instruments.

9. What are the manifestations of abnormal animal behavior?

Answer: Many earthquake cases indicate that animals are "live instruments" for observing earthquake precursors. They often have various abnormal behaviors before the earthquake and indicate to people that the disaster is approaching. At present, hundreds of animals have been found to have abnormal performance before the earthquake. Among them, there are more than 20 kinds of abnormal reactions. The most common animal anomalies are: - Frightening reactions such as large animals do not enter the circle, dog barking, birds or Insects fly, abnormal - inhibitory abnormalities such as behavior become sluggish, or hairpin crazy, be at a loss; or refuse to eat. - Changes in living habits such as hibernation of the snake out of the hole, mice are not afraid of activities during the day, a large number of frogs and other activities.

10. Are animal behavior abnormalities related to earthquakes?

Answer: Not necessarily. Because there are many factors that cause animal anomalies, such as changes in the weather, environmental pollution, improper feeding, and the animals themselves, such as illness, pregnancy and so on. Therefore, the abnormal performance of animals is not necessarily an earthquake precursor. In addition, sometimes (especially after a strong earthquake), people's emotions are over-stretched, and they may also have an illusion when observing animal behavior. Therefore, do not panic after discovering anomalies and report them to the earthquake authorities in a timely manner.