Main work deployment

The main work has been described in the general outline, and the key issues will be selected for detailed discussion below.

(a) the construction of seismic geology and earthquake prediction test base

Its main goal is to break through the difficulties of earthquake prediction. It is planned to build six earthquake prediction test bases in the west of Chinese mainland, of which the central part is the north-south seismic tectonic belt; A few years later, the eastern mainland entered an active period of earthquakes, and then related test bases were built. After a breakthrough in earthquake prediction in mainland China, we went to Taiwan Province Province to carry out earthquake prediction research and comprehensive monitoring.

1. Basic research ideas of earthquake prediction

Professor Li Siguang clearly pointed out that he mainly answered two questions in the earthquake prediction work of Seismogeological Research []:

(1) Where is the active tectonic belt? How does it move?

Its contents include: finding out the position of active tectonic belt; Track the direction and scope of its extension; Determine the activity degree and frequency of the active tectonic belt; Determine the nature of the active tectonic zone; Try to find out other structural zones closely related to an activity.

(2) How did the activity of the tectonic belt cause the earthquake?

The seismic source "wanders" in the active tectonic belt, generally moving at one point or several points, that is, some parts with special structural forms in the belt are regarded as dangerous places where earthquakes may occur.

According to Li Siguang's experience in earthquake prediction after the 1966 Xingtai earthquake in his later years, it can be concluded that seismic geological work can be used to predict large earthquakes, and the active structural zone of large earthquakes should be found first; Then the position of the dangerous section in the belt is determined by measurement; Then, according to the research methods and steps of rock mechanics and tectonic stress field, a monitoring network is set up to monitor the development and evolution of tectonic stress and energy concentration, so as to predict major earthquakes. According to the sequence of these three steps, the prediction of major earthquakes is realized, as follows:

The first step is to carry out short-and medium-term seismic geological analysis and research to predict the migration and development trend of large earthquakes in active tectonic zones.

The second step is to carry out geological exploration of the tectonic background of seismic geology, deep structural drilling, and research on the current activity law of structures, and determine the dangerous position of large earthquakes on the basis of finding out the seismogenic structural system and earthquake-controlling structures.

Thirdly, according to the idea and method of tectonic stress field in rock mechanics, a comprehensive monitoring station network of tectonic stress is established with the dangerous place of large earthquake as the center, so as to monitor the whole process of in-situ stress and energy accumulation and concentrated development in real time, fully grasp the opportunity of earthquake occurrence, discuss and discuss the three elements of earthquake risk (location, magnitude and time) in time, report to the higher authorities in time, and the relevant state departments issue the earthquake forecast.

2. The tectonic stress field of large earthquake is an additional regional tectonic stress field.

The tectonic stress field of the great earthquake discussed here is an independent and complete regional tectonic stress field, which can be superimposed (or attached) on the global tectonic stress field. It has its own independent integrity and its own development and formation process, that is, in the middle of process of crustal movement, some parts with special structural forms in the active tectonic belt start from earthquake preparation (tectonic stress and energy concentration), and then accumulate and accelerate to maturity (formation). Then it reaches the stress intensity that the structure and rocks of the location (earthquake source) can't bear, and suddenly releases structural stress and energy, that is, a major earthquake occurs, causing strong crustal vibration, ground motion, sand gushing and water gushing. And then continue to release the pressure and energy for many years, aftershocks continue to appear, and at this time it has entered the post-earthquake adjustment stage. It can be clearly divided into: pre-earthquake accumulation stage, earthquake eruption stage and post-earthquake adjustment stage, which is a complete process of pre-earthquake geostress, concentrated energy accumulation-earthquake release-post-earthquake adjustment. It is also the whole process of the preparation, formation, occurrence and adjustment of the great earthquake and the whole process of the development and deepening of the tectonic stress field in the additional area of the great earthquake. It is a major earthquake event in some parts of process of crustal movement (Figure 8- 1)[ 1-6, 18].

Figure 8- 1 Schematic diagram of additional superposition relation of tectonic stress field

3. Prediction and analysis of recent trend of Kunming-Chuxiong earthquake in Yunnan.

Migration of earthquakes in recent years (1)

In 2008, the Wenchuan M8 earthquake in Sichuan occurred in the middle of the north-south seismic belt in central China, that is, the Longmenshan active fault zone in northeast China. After the discussion in the previous chapter, it is determined that the earthquake of magnitude 8 will migrate to the north and south ends along the north-south seismic tectonic belt.

The above-mentioned earthquake prediction opinions were exchanged and discussed at the "Li Siguang Geological Science Award Foundation and National Earthquake Symposium" held in Beijing in May 2008 after the Wenchuan earthquake in Sichuan, and have been tested for more than several years. The situation is as follows:

① On August 3rd, 2008, an earthquake of magnitude 6. 1 occurred at the junction of Renhe District and Huili, Panzhihua City, Sichuan Province.

② On July 9, 2009, an earthquake of magnitude 6 occurred in Chuxiong Prefecture and Yao 'an, Yunnan Province, with a focal depth of 10km.

③ On June 3rd, 2009 165438+ Binchuan County, Dali, Yunnan Province, an earthquake of magnitude 5 occurred with focal depth of 10km.

④20 10 On February 25th, 2000, an earthquake of magnitude 5. 1 occurred at the junction of Chuxiong, Lufeng and Yuanmou in Yunnan, with a focal depth of 16km.

Two earthquakes of magnitude 6 have successively moved to Dali, Yunnan, and reached the west side of Kunming, Yunnan, indicating that after the Wenchuan earthquake in 2008, the north-south seismic tectonic belt in Central China is still active today, with strong earthquakes moving directly to the vicinity of Kunming, and earthquakes of magnitude 4 ~ 5 have also been active in this area in recent years. All these signs of seismic activity show that the risk of an earthquake of magnitude 7 near Kunming will increase in the near future. Therefore, it is also suitable to be selected as the test base for capturing large earthquakes (Figure 8-2)[23].

Fig. 8-2 Analysis diagram of migration trend of major earthquakes in recent major danger areas of China North-South seismic tectonic belt and Chinese mainland earthquake with magnitude above 7.

(2) Basic laws of historical earthquakes

According to the distribution relationship between historical earthquakes and main faults in Yunnan Province (Figure 8-3), many historical earthquakes are controlled by the north-south (meridional) structure, and the major earthquakes in the southern "Sanjiang" area are mainly controlled by the northwest arc main fault.

Now choose Kunming-Chuxiong nearby, and some historical earthquake archaeological data are summarized as follows [24]:

①1September 9, 680 Chuxiong earthquake, Yunnan province, with magnitude A and moderate intensity VII (Figure 8-4).

②1July 7, 696, Kunming earthquake, Yunnan, with magnitude A and moderate intensity VII (Figure 8-5).

③1The Xundian earthquake in Yunnan on February 26th, 773, with magnitude A and moderate intensity VII (Figure 8-6).

④ 65438+65438+1October 8, 20725 Songming and Yiliang earthquakes in Yunnan, with magnitude A and epicenter intensity VII (Figure 8-7).

⑤1August 2, 733 Southwest Huize earthquake in Yunnan, with magnitude A and epicenter intensity X.

⑥ September 1750 Chengjiang earthquake in Yunnan, magnitude A, epicenter intensity VIII (Figure 8-8).

Figure 8-3 Outline of Three-layer Control Range for Kunming-Chuxiong Earthquake Prediction in Yunnan.

⑦176365438+On February 30th, an earthquake occurred near Jiangchuan, Yunnan, with a magnitude of A and an epicenter intensity of VIII degrees (Figure 8-9).

⑧1June 7, 789, Huaning and Tonghai earthquakes in Yunnan, with magnitude 7 and epicenter intensity VII (Figure 8- 10).

Pet-name ruby1September 6, 833, an earthquake occurred in Songming and Yanglin, Yunnan, with magnitude 8 and epicenter intensity VII.

Attending1887 65438+February 16 Shiping southeast Yunnan earthquake, magnitude 7, epicenter intensity VII (Figure 8- 1 1).

(1 1)1May, 9091southwest Yunnan Maitreya earthquake, magnitude A, epicenter intensity VIII (Figure 8- 12. )

Figure 8-4 Historical Earthquake in Chuxiong, Yunnan [24]

Figure 8-5 Historical Earthquake in Kunming, Yunnan [24]

Figure 8-6 Historical Earthquakes in Xundian, Yunnan Province [24]

Figure 8-7 Historical earthquake between Songming and Yiliang in Yunnan [24]

Figure 8-8 Yunnan Chengjiang Historical Earthquake [24]

Figure 8-9 Historical Earthquakes in Tonghai and Jiangchuan, Yunnan [24]

Figure 8- 10 Huaning and Tonghai Historical Earthquakes in Yunnan [24]

Through the analysis of the above historical earthquake data, we can see that:

● The vicinity of Kunming-Chuxiong in Yunnan Province is an earthquake-prone area, where large and moderate earthquakes have occurred continuously in history, which belongs to the earthquake danger zone.

The long axis direction of historical earthquake intensity isoseismic line is mostly near the north-south direction, indicating that the seismogenic structure may belong to the north-south direction.

4. Seismogeological investigation and exploration of Kunming-Chuxiong earthquake danger zone in Yunnan.

(1) The main goal is to find the seismogenic active structural system, which is likely to be the north-south active structural belt (i.e. the central meridional structural belt); At the same time, find out the earthquake control structure. The latter often "locks" the former, making it unable to move freely, resulting in a high concentration of in-situ stress and energy in the "locked" part, and may also be the source of future major earthquakes, and the projection on the surface is the epicenter position. Therefore, the main goal of seismic geological survey and exploration is to identify the polar earthquake areas where major earthquakes may occur in the future and control the earthquake prediction network around them.

(2) Seismic geological exploration should not only find out the surface and hidden geological structures, but also trace back the deep geological structures, that is, the structural background of deep earthquakes in the crust, that is, find out the geological structures near the source as much as possible, mainly through geophysical exploration and analysis, and verify them through deep drilling.

Figure 8- 1 1 Historical earthquake in the southeast of Shiping, Yunnan [24]

Figure 8- 12 Yunnan Maitreya and Southwest Historical Earthquakes [24]

5. Study on current tectonic activity system, rock mechanics and tectonic stress field in Kunming-Chuxiong earthquake danger zone.

While controlling the Kunming section of the North-South seismic tectonic belt in Central China, we will set up a comprehensive survey network profile of east-west monitoring geostress near Xichang in the north, Panzhihua in the middle and Tonghai in the south to monitor its current activities, compare it with the east-west profile network of Kunming-Chuxiong, and study the problem of large earthquake danger zone near Kunming-Chuxiong on the basis of providing comparative information for earthquake prediction (see Figure 8-3).

After knowing the seismogenic structure and earthquake-controlling structure, the key is their current activities. If they are not active, there may not be a big earthquake. If the in-situ stress cannot be formed as soon as possible and the energy is highly concentrated, it is impossible to have a big earthquake soon. Therefore, it is the primary task to study the law, development and evolution of rock mechanics and tectonic stress field. At the same time, the arrangement of stations for monitoring and predicting earthquakes also needs to be based on the research field, mainly in the "sensitive" and "window" positions of the site, and the effect is better.

The study of current tectonic activity and current tectonic stress field should be divided into three levels (see Figure 8-3):

(1) Small-scale research, seismogeological research and analysis generally study the current regional tectonic activity and the current tectonic stress field outline in the large-scale scope of 1: 1 10,000 provinces and regions, mainly collecting data and mapping, aiming at mastering the movement characteristics and basic laws of the main active tectonic systems.

Put Kunming-Chuxiong in the center of the map, and draw the relationship map between Yunnan and its adjacent areas 1: 1 million active tectonic system and earthquakes. Taking Kunming-Chuxiong as the center, with a radius of 300 kilometers, the regional structural map, structural system and structural outline map, historical earthquake catalogue and epicenter distribution map, historical earthquake archaeological intensity distribution map, earthquake sequence change map, focal mechanism solution, regional geostress measurement data, regional GPS deformation data, regional fault displacement measurement data, regional geothermal hot spring catalogue and distribution map, coal and gas outburst and rockburst catalogue and distribution map are collected for comprehensive mapping. Collect geodetic and retest data, and draw up the regional crustal deformation map (Figure 8- 13, Figure 8- 14).

(2) Study on regional seismogeology at medium scale (1:200,000). With Kunming and Chuxiong as the center and 200 kilometers as the radius, the geological structure and structural system of1:200,000 or1:250,000 are mapped, with the purpose of finding out the regional seismic geological activity law and the current activities of the earthquake-causing structural system and earthquake-controlling structure.

On the basis of data collection, field investigation and preliminary geological exploration are carried out to find out the outline characteristics of the main body of geological structure, and combined with deep exploration, the general situation of geological structure in the exploration department is preliminarily found out. Analyze and study the occurrence law of historical earthquakes.

On the basis of collecting data of ground stress, ground deformation, fault displacement, focal mechanism, historical earthquakes and various internal geological disasters, the deep-hole investigation of regional ground stress is carried out to understand the changes of ground stress in plane and depth, and regional ground deformation, GPS and fault displacement monitoring reference stations are set up to analyze the current activity law of regional main structural systems. Through simulation experiments, the sequence diagram of tectonic stress field is drawn.

(3) Large-scale (1:50,000) regional seismogeological research. With Kunming and Chuxiong as the center and 100km as the radius, the seismogeological map is compiled, including geophysical exploration, drilling and trench exploration for the main structural systems, developed structures and earthquake-controlled structures, so as to find out the deep structures.

Carry out deep-hole structural stress measurement, cooperate with three-dimensional structural simulation experiment, and compile the research result map of three-dimensional structural stress field; The current fault displacement field is simulated and analyzed by using the flow displacement measurement data, and the current tectonic topographic map is compiled. Compile a comprehensive map of three-dimensional tectonic stress field, discuss the location, orientation and depth of earthquake source, evaluate the magnitude of earthquake, possible ground intensity and distribution range (including high intensity distribution area of seismogenic structural system), evaluate the location and intensity distribution of large aftershocks, and evaluate the degree of damage, so as to provide information for disaster prevention and mitigation.

The time of the earthquake has become the focus of the next study. The key is to deploy monitoring network and complete large-scale large-scale seismic geological map series.

Figure 8- 13 Comprehensive Analysis Example of Recent Regional Tectonic Activities

7. Establishment of the organization of the seminar on earthquake geology and earthquake prediction and formulation of the work schedule system.

8. Establish disaster reduction and prevention mechanisms and carry out mass monitoring and prevention work, establish communication channels with local governments, and establish channels for reporting earthquake prediction to the state.

9. Construction of earthquake prediction test base

In addition to the construction of Kunming-Chuxiong earthquake prediction experimental base in Yunnan, several experimental bases should be built: Tianshui-Yinchuan primary base in Gansu, Kashgar primary base in Xinjiang, and anti-S primary base in Qinghai-Tibet. Prediction and demonstration of seismic activity trend in the medium and near future, seismic geological analysis and discussion, field investigation, preliminary analysis of rock mechanics and tectonic stress field, etc. The site selection and implementation of the experimental base were carried out respectively.

It should be reminded that earthquake prediction is a very arduous task, and the types of earthquakes in the seismic tectonic stress field are also diverse. After a success, it is also very difficult to acquire knowledge. Therefore, we must succeed every time, and we must have systematic and sufficient scientific data to prove that practice is successful. Only in this way can we gain everyone's knowledge. For example, the prediction of 1975 Haicheng earthquake is an example, and it is very successful to predict large earthquakes with small earthquakes; However, the Tangshan earthquake 1976, the second application of "small earthquake reporting big earthquake" will not work [18-23]!

(2) The application of "safe island" theory and practice in urban agglomerations and important economic zones-the idea and arrangement of comprehensive evaluation of regional crustal stability.

The three major urban agglomerations and important economic zones in the eastern mainland of China, namely, the Hong Kong-Guangzhou Pearl River Delta Economic Zone, the Shanghai-Nanjing-Hangzhou Yangtze River Delta Economic Zone and the Beijing-Tianjin-Shenyang Bohai Rim Economic Zone, all need the guidance of the "safe island" theory-the research results of comprehensive evaluation of regional stability. The following will take the Yangtze River Delta economy as an example [1-6] for discussion and discussion.

1. Guiding ideology and comprehensive evaluation ideas

In the past, the "safe island" theory-comprehensive evaluation study of regional stability was called regional crustal stability evaluation study. In essence, structural stability evaluation is emphasized as the main body, and earthquake disaster research and fortification are emphasized, while medium stability evaluation research (rock mass stability and soil stability evaluation research) and foundation stability evaluation research are in a secondary position. At present, we should investigate and study first, focus on solving the problems existing in this area, and solve the problems in the evaluation and research in turn. In the evaluation of structural stability, various internal geological disasters and their related problems are discussed comprehensively. In short, expand the scope of research content as much as possible, and achieve the principle of seeking truth from facts and solving problems until the reasonable planning and construction is completed.

Using the ideas of earthquake geology, rock mechanics and tectonic stress field, taking solving all kinds of geological disasters as the guiding ideology, through geological investigation and detailed investigation of exploration procedures, according to the order of small, medium and large evaluation and research, concrete conclusions are given to various main problems existing in the region until a reasonable planning and construction map is completed, and quantitative comprehensive evaluation and report writing are carried out.

Flood disasters and environmental problems have not been paid enough attention in the past, so we should further study and put forward specific measures to solve the problems in the future.

2. Study on seismic geology and structural stability evaluation.

The seismic intensity of the Yangtze River Delta Economic Zone is ⅷ, but the fortification intensity of buildings in this area is generally low or even unprotected. Therefore, through the seismic geological investigation and exploration research in this area, and on the basis of finding out the seismogenic structural system of magnitude 6 or so and the historical seismogenic structural background, this paper analyzes the specific distribution range of the intensity zone that may reach VIII in the future, determines the seismic intensity of key projects, densely populated towns, traffic arteries, industrial parks, etc., and studies the possibility of other internal dynamic disaster activities, so as to ensure safe construction and live and work in peace.

Based on the study of rock mechanics and tectonic stress field, combined with deep, new and dynamic exploration research, the three-dimensional field modeling is realized, and the four-dimensional law research is completed combined with the study of historical earthquake development sequence. A certain number of comprehensive monitoring networks of ground stress, ground deformation and fault displacement are arranged for continuous monitoring to monitor moderate earthquakes in sudden earthquakes.

3. Use and deployment of different research scales for seismic geological evaluation.

(1) A small-scale seismic geological mapping of 1: 1 10,000 was carried out in the whole region.

(2) Carry out1:200,000 medium-scale seismic geological survey and exploration verification research in key areas.

(3) Carry out large-scale seismic geological exploration research and quantitative evaluation in key areas1:50,000. Formulate detailed plans for cities, industrial layout, transportation, lifeline projects, nuclear power projects, environmental geology, etc., and rationally develop and utilize land.

4. Research on environmental geological planning

In addition to internal dynamic geological disasters, environmental pollution, floods, underground seawater intrusion, land subsidence and many other problems, as well as soil stability in some areas, should be taken as research objectives, especially environmental pollution should be considered in the site selection of hazardous chemicals bases.

5. Reasonably adjust the overall layout of the Yangtze River Delta Economic Zone.

We should give consideration to long-term sustainable development and security, and at the same time, we need to make a concrete assessment of the possible mineral development in this area, and the research and assessment of adjacent sea areas should also be included in the research agenda. In short, comprehensive planning, comprehensive evaluation research and real-time monitoring research are the key points of the Yangtze River Delta Economic Zone.

The quantitative evaluation of regional crustal stability has accumulated some experience. On this basis, it is necessary to expand the scope of services and fully implement all aspects of technical services.

(3) Establish an international exchange and open research center for in-situ stress measurement.

Other relevant chapters in this book have described the proposal of establishing an international open research center for geostress measurement and the development and standardization of new geostress measuring instruments, which are repeated here [23-24].

(4) New methods and technologies for deep-hole geostress measurement, research, development and implementation of ultra-deep drilling (focal depth).

The new method and technology of deep-hole geostress measurement, the research and development and implementation plan of ultra-deep drilling (focal depth) are obviously the focus of long-term planning, and are the pillar project planning of "underground development research", which is of epoch-making significance to geostress research. Some discussions have also been made in the relevant chapters of this book [1-23].