How difficult is it to predict earthquakes?

Earthquakes are predictable, but difficult. In the mid-1970s, China successfully predicted the Haicheng earthquake of magnitude 7.3 in Liaoning, which was the first successful earthquake in the world. Later, it was predicted that the earthquake of magnitude 7.2 in Songpan, Sichuan Province. In the middle and late 1990s, China made short-term and imminent predictions for the earthquake with M = 7.3 on the China-Myanmar border and the earthquake with M = 5.6 in Haicheng, Liaoning Province, and achieved good disaster reduction results, which made China a world leader in earthquake prediction science. However, these successful predictions are still empirical. At present, although we can predict some types of earthquakes to some extent, we cannot predict all destructive earthquakes, and earthquake prediction is still a world scientific problem in the process of exploration. Because the preparation and occurrence of earthquakes is a very complicated process, there will be various abnormal phenomena in geophysical, geological, geodetic, geochemical, biological, meteorological and other fields in this process. After systematic cleaning and research, since the 1966 Xingtai earthquake, more than 70 moderate earthquakes in China have recorded more than 1000 earthquake precursors. These precursory anomalies can be divided into ten categories, namely seismology, crustal deformation, gravity, geomagnetism, geoelectricity, hydrogeochemistry, dynamics of underground fluids (water, steam, gas and oil), stress and strain, meteorological anomalies and various macroscopic precursory phenomena. Each precursor also includes a variety of monitoring methods and abnormal analysis items. For example, crustal deformation includes large-area leveling, fault displacement measurement, sea level observation, lake surface observation and ground inclination observation. Seismological precursory analysis is the most abundant of all kinds of precursors, with more than 30 analysis methods. Macro abnormal projects are more colorful. In a word, due to the complexity of earthquake preparation and occurrence, earthquake precursors are rich, diverse and comprehensive, which can be summarized into ten categories and nearly 100 items. Predicting a destructive earthquake in a certain area within ten years is called long-term earthquake prediction; The prediction of destructive earthquakes that may occur in a certain place within one or two years is called medium-term prediction; Medium-term prediction and long-term prediction of earthquakes are collectively called medium-and long-term prediction. The prediction of destructive earthquakes that may occur in a certain place within one or two months is called short-term prediction; The prediction of a destructive earthquake that may occur in a certain place within a few hours to a few days is called imminent earthquake prediction. (2) Study the law of historical seismic activity. Find out the period of seismic activity and study the relationship between earthquakes that have occurred in history and active tectonic zones today. (3) Observation by station instruments. Precise observation around the fault zone that determines the current activity can obtain valuable information about the current crustal structure changes, infer the development trend of earthquakes, and sometimes find out the possible location of the source. The records of earthquakes in the history of our country were first found in bamboo annals. One of them mentioned that "Xia" caused seven earthquakes in Mount Tai, saying that an emperor named "Fa" in Xia Dynasty boarded Mount Tai in Shandong Province in the seventh year of his accession to the throne (BC 183 1 year), and an earthquake happened in Mount Tai. Another place mentioned Xia Jie's "Ten Years, ... The night stars fell like rain and the earthquake exhausted Elo", that is to say, there was an emperor named "Jie". In the tenth year of his accession to the throne (BC 1809), the meteor in the sky fell one night. This year, there was an earthquake in western Henan. After the earthquake, the water in yi river and Luohe dried up. The time interval between these two earthquakes is now more than 3,800 years, which is not only the earliest earthquake record in China, but also the earliest earthquake record in the world. Many strange changes in nature are not all precursors of earthquakes. Therefore, after finding anomalies, special attention should be paid to distinguish them from non-seismic interference factors. Generally speaking, the causes of non-earthquake animal anomalies are weather changes (such as fish floating and frog migration), physiological changes (sick estrus) and environmental changes (water pollution). The causes of non-seismic groundwater anomalies are climate change, hydrology, geology and human interference. When judging whether it is a macro anomaly or not, we should consider the characteristics of earthquake macro anomalies: these precursors are controlled by geological structures, which are banded, quadrant-shaped or consistent with the direction of local structural lines, and the precursor phenomena in the epicenter area will be relatively dense in the future; These anomalies are synchronous in time, concentrated in number, diverse in types, wide in scope, large in number and strong in response. Only by finding anomalies and correctly eliminating interference can we grasp the opportunity and make effective predictions. In the mid-1960s, Japan, the United States, the Soviet Union and other countries successively applied modern science and technology to carry out earthquake prediction research. Since the 1966 Xingtai earthquake, China has also started earthquake science experiments, basically at the same time as Japan, the United States and the Soviet Union. After more than 30 years of exploration, great progress has been made in earthquake prediction research. However, the scientific problem of earthquake prediction has not been broken through internationally. Compared with Japan and the United States, China's earthquake prediction research is inferior to them in observation technology, equipment, communication technology and data processing technology, but China has advantages over Japan, the United States and the Soviet Union in the following aspects. First, they can't compare the data of major earthquakes in China, the observed precursor phenomena and the accumulated prediction experience. Secondly, on the basis of summing up the experience of earthquake prediction, the criteria, indicators and methods of earthquake prediction and the technical procedures of earthquake prediction are further studied, which has taken a big step forward in practical application, while other countries are still trying or in the experimental stage in some fields. During the climax of the China earthquake in 1970s, we made good predictions about Haicheng earthquake and Songpan earthquake, and achieved the effect of reducing earthquake disasters, which is unprecedented in the world. However, although great progress has been made in earthquake prediction in China, the current prediction level is still very low, and only a few earthquakes can be predicted. Therefore, on the basis of great progress, we should further carry out theoretical and experimental observation and research, and strive to overcome this worldwide problem as soon as possible. Because earthquake prediction has a wide range of social influences, it is very serious to determine earthquake prediction opinions and publish earthquake predictions. It is not simply a scientific problem, but a social problem with wide influence. Therefore, in order to make earthquake prediction have laws to follow, the State Council issued the Regulations on the Administration of Earthquake Prediction in 1998. The Regulations on the Administration of Earthquake Prediction stipulates that the state shall implement a unified publishing system for earthquake prediction. Earthquake prediction must be issued by the people's governments of provinces, autonomous regions and municipalities directly under the Central Government according to their authority. No unit or individual, including earthquake departments and earthquake workers, has the right to release earthquake predictions to the society. Regarding the authority to issue earthquake prediction, the Regulations on the Administration of Earthquake Prediction stipulates that "the long-term and medium-term earthquake prediction of the whole country shall be issued by the State Council." "Long-term prediction, medium-term prediction, short-term prediction and imminent earthquake prediction within the administrative areas of provinces, autonomous regions and municipalities directly under the Central Government shall be issued by the people's governments of provinces, autonomous regions and municipalities directly under the Central Government.