According to Xinhua News Agency, Beijing, December 19, at 23:59 Beijing time on December 18, a 6.2-magnitude earthquake occurred in Jishishan County, Linxia Prefecture, Gansu Province, with an epicenter depth of 10 kilometers. So far, the earthquake has caused 100 deaths in Gansu and 11 deaths in Qinghai, and the number of people affected is being further investigated, and some water, electricity, transportation, communications and other infrastructure have been damaged, and Gansu Province is making every effort to organize rescue.
What are the difficulties in earthquake forecasting? What are the areas with high earthquake occurrences, and what can people do on a daily basis to prevent earthquake disasters?
Shen Xuhui, a researcher at the Institute of Crustal Stress of the China Earthquake Administration
Sun Shihong, a researcher at the China Earthquake Network Center
I once asked the surging guest, popularizing the knowledge of earthquake prevention and disaster reduction for netizens.
The difficulty in earthquake prediction is there
@空空不空: Why can't we predict the likelihood of an earthquake a few days in advance, just like weather forecasting?
Shen Xuhui: As a scholar engaged in earthquake research, I actually have the same doubts as you, when will the level of earthquake prediction be the same as that of weather forecasting? At present, the difficulty of earthquake prediction mainly exists in the following points:
First, seismic research is an observational science, which needs to carry out statistical induction based on a large amount of observational information and gradually form corresponding research methods, which are verified and revised through repeated accumulation, and finally developed into a complete prediction method. Unfortunately, from the perspective of scientific research, the probability of a major earthquake is too small, and it is difficult for a scientist to obtain many valid research samples in his lifetime, and it is difficult to form statistical laws and verify prediction methods.
Second, earthquakes occur deep underground. So far, we have not been able to actually observe what is happening inside the hypocenter, and we have to rely on some inversions, speculations, and assumptions to carry out analysis. At present, it is urgent to learn from the achievements of related disciplines to understand the physical and chemical processes of the hypocenter in the ultra-high temperature and ultra-high pressure environment, and help to develop the hypocenter process model.
Third, our observational capabilities remain limited. Scientists have been trying to reach deep underground, but the truth is that "it is easy to go to the heavens and difficult to enter the earth", and our ability to enter the earth is still very insufficient. On the other hand, global earthquakes mostly occur in the sea, while continental earthquakes mostly occur in the Qinghai-Tibet Plateau and its surroundings, and the natural conditions are limited, which is not conducive to systematic observation, resulting in some of the small earthquakes mentioned above not being observed. Currently, we are developing a space Earth observation system (GEOSS) that we believe will provide important support for significantly improving the ability to obtain seismic cases in a global manner.
Finally, earthquake prediction research is a systematic project, and perfect information acquisition capabilities, high-performance data processing capabilities and innovative scientific models are the three cornerstones of the development of earthquake prediction science.
@朝雨: Was the earthquake accidental or inevitable?
Shen Xuhui: My understanding: earthquakes are sporadic but inevitable. The earth, like us humans, has life. Previous studies have shown that the earth was formed billions of years ago and is currently in its prime, and natural phenomena such as earthquakes are a manifestation of the vitality of the earth.
General understanding: Earthquakes are the result of the movement of the Earth's tectonic plates, especially their interactions and their transmission over long distances into the interior of the plates. When this action hits some weak areas on the earth's surface, it will lead to increased deformation and even sudden stress release, resulting in the formation of earthquakes.
Earthquakes and plate movements are manifestations of the vitality and dynamics of the Earth's interior. This vitality and motivation are also sufficient and necessary conditions for the survival and development of life on Earth, including human beings.
@付出了几分: Why are earthquakes frequent in Sichuan?
Sun Shihong: The distribution of strong seismic activity on the mainland is that Taiwan has the strongest seismic activity. In the 20th century, there were 41 earthquakes of magnitude 7 or higher in Taiwan, accounting for 35% of the total number of earthquakes of magnitude 7 or higher in the mainland. As far as the continental continent is concerned, the intensity and frequency of seismic activity in the western part of Chinese mainland west of 107°E longitude are greater than those in the eastern part of the continental continent due to the strong collision directly affected by the Indian plate. In the 20th century, there were 64 shallow earthquakes of magnitude 7 or higher on the mainland continent, 56 in the western part of Chinese mainland west of 107° east longitude, accounting for 87.5%, and the seismic energy released accounted for more than 95% of the entire continent. However, the strong seismic activity of the continent has an active and calm alternating process in the time domain. It can only be said that in the past ten years, Sichuan has just been in the active period of strong earthquake activity.
How to protect against earthquake disasters
@贝己塔: Can earthquakes be prevented?
Shen Xuhui: Earthquakes cannot be prevented, but earthquake disasters can be prevented.
The prevention of earthquake disasters is a scientific and technological problem that many disciplines such as earthquake science, engineering mechanics, civil engineering, and urban and rural planning have been committed to tackling for a long time, and many achievements have been made. Here are a few examples:
1. There are active faults underneath many cities in the mainland. On the basis of studying the characteristics of fault activity and its hazards, the land use in the area near the fault can be reasonably planned, for example, Yinchuan City designed to design the fault zone along the fault zone as a park and green space, and carried out earthquake resistance and earthquake prevention knowledge publicity.
2. Study and adopt seismic absorption and isolation measures for special buildings.
3. More research is on the possible damage caused by earthquakes, and the corresponding seismic reinforcement measures for buildings. Earthquake resistance according to regional characteristics and the importance level of buildings has become a basic practice for earthquake prevention in various parts of the mainland.
@nananan: What advice do you have on subsidy policies and building materials for areas where earthquakes are frequent?
Sun Shihong: First, we should build as strong a house as possible according to the local economic conditions. The construction of the house should meet the local seismic fortification requirements, the seismic design should be carried out according to the national mandatory standards, and the construction quality should be strictly guaranteed.
The second is to strengthen the popularization of earthquake science. The current earthquake science popularization in our country needs to be strengthened from strength to teaching materials, and lacks universality and pertinence. This is a real matter that the government should pay attention to. Personally, I think that it is better to spend hundreds of millions of dollars on the system than to invest money in improving the quality of people.
I think the above two points are key.
@肥超: Apart from Sichuan, where else are there earthquake-prone areas in China, and how can earthquake disasters be mitigated?
Sun Shihong: The seismic activity on the mainland is mainly distributed in 23 seismic zones in five regions. The five regions are:
1. The Qinghai-Tibet Plateau earthquake zone, including Yunnan, Sichuan, Qinghai, Tibet, Gansu and other regions, is the area with the strongest seismic activity and frequent major earthquakes. According to statistics, there have been 9 earthquakes of magnitude 8 or above and 78 earthquakes of magnitude 7~7.9 in the mainland of this earthquake area, ranking first among the five major earthquake areas.
2. Tien Shan, Altai seismic zone. The seismic area is divided into four seismic zones: the South Tianshan Mountains, the Middle Tianshan Mountains, the North Tianshan Mountains and the Altai Mountains.
3. North China Earthquake Zone. The earthquake intensity here is high but the frequency is relatively low, and the strong earthquakes are mainly distributed in five seismic zones in this seismic zone, from east to west, the lower reaches of the Yangtze River - the Yellow Sea seismic zone, the Tanlu seismic zone, the Hebei Plain seismic zone, the Fenwei seismic zone, and the Hetao Yinchuan seismic zone.
4. The South China earthquake zone is mainly distributed in the southeast coast and the Taiwan Strait. The area can be divided into the seismic zone in the middle reaches of the Yangtze River and the southeast coastal seismic zone.
5. Taiwan Earthquake Zone.
Earthquake disaster mitigation is a systematic project, which mainly includes:
1. Formulate and improve laws and regulations on earthquake prevention and disaster reduction, earthquake resistance of buildings (structures) and post-earthquake reconstruction, and formulate and improve national, industry and local standards for earthquake prevention and disaster reduction and earthquake resistance of buildings (structures);
2. Strengthen earthquake monitoring and forecasting and seismic research on buildings (structures);
3. Governments at all levels and major enterprises should formulate earthquake emergency plans, mainly to set up an earthquake relief command system, formulate evacuation routes and establish safe shelters, formulate health and epidemic prevention plans and transfer plans for the wounded and sick, formulate emergency and control plans for transportation and communications, and formulate plans for the prevention of secondary disasters such as earthquakes;
4. Regularly carry out propaganda and lessons on earthquake prevention and disaster reduction knowledge for the broad masses of the people, especially strengthen publicity and education for primary and secondary school students, and organize earthquake prevention and disaster relief Xi drills of different scales.
The main objects of earthquake early warning are major facilities and lifeline projects, such as nuclear power plants, gas pipelines, subways, high-speed trains, etc. Earthquake early warning is the preemptive warning of impending disasters and urgent action when a devastating earthquake has already occurred.
@OvO: What is the general seismic rating of high-rise buildings with current tower structures?
Sun Shihong: The seismic capacity of houses has different requirements for different regions. Housing construction in Beijing is required to withstand earthquakes with an intensity of eight (equivalent to 6.5 magnitude). According to the guidelines for the seismic design of residential houses in mainland China, when your house encounters a seismic intensity less than or equal to the seismic fortification requirements, it will not be damaged or can still be used after minor repairs. If an earthquake is more than one degree stronger, your house will still be able to withstand collapse.
For brick-concrete and reinforced concrete frame houses, the higher the house, the higher the damage rate in the event of an earthquake.
However, due to the large scale and large investment of super high-rise or skyscrapers, the requirements and grades are set quite high during the design, and the overall collapse is basically impossible.
It should be noted that when a major earthquake occurs, the damage to the house in the vicinity of the fault is greatly exacerbated.