The eyes of Wenchuan and Yushu earthquakes

At present, the problem of earthquake prediction is heating up, and various prediction methods emerge one after another, from orthodox geological methods to the study of XX anomalies (including groundwater level anomalies, animal anomalies, and some superhuman sensory anomalies). Nature magazine published an article about the abnormality of toad, and the superhuman deeds of improving the sixth sense, the seventh sense and the eighth sense in various places were also hotly discussed by the media. Although I am not a student majoring in geosciences, I have learned a lot about earthquake prediction methods in detail.

First of all, the earthquake is a scientific problem. To grasp this problem in essence, we must first grasp the scientific system as a whole, so as to clearly understand the current level of earthquake prediction, some misunderstandings and development trends.

The basic picture of the whole scientific system: 1. First of all, the scientific system is hierarchical: quantum mechanics is at the bottom, classical physics and chemistry are above, and natural sciences such as biology and earth science are above. Basic disciplines can provide conceptual and instrumental guidance and help for high-level disciplines. 2. Each discipline has its own scale. There are unique basic laws that cannot be (see appendix) and do not need to be derived from more basic laws (but concepts and tools may need to be provided by more basic disciplines). In this discipline, other complex laws and phenomena can be derived from such basic laws in principle (that is, there is no new basic law in essence above the basic law), but due to the limitation of practical computing power and other factors, it cannot be completely achieved. This is also the reason why the empirical laws and primary models of various disciplines are valuable. Even so, it is basically necessary to find a level of the unique basic laws of nature and make full use of the concepts and tools of the underlying disciplines for research.

With the above understanding, I now define the most basic law of a discipline (a level) as the "first law". At this level, the "first law" (cause) and the phenomenon to be predicted (result) are in one-to-one correspondence. Hooke's law, for example, shows that the result-spring force and the cause-spring elongation are in one-to-one correspondence, and the spring force cannot be due to other reasons. A force will only lead to a kind of airflow movement, which will lead to a unique weather condition. But I call it a "non-basic law" (including empirical law and primary model) which is more complicated than the "first law", and it treats the phenomenon to be predicted one-to-many. For example, judging the trend of temperature and wind direction in the second stage of weather forecast, because different fluid conditions may form similar trends, which are one-to-many and because of force and weather. Therefore, trends and weather conditions are one-to-many, so the accuracy of judging the weather through trends is definitely not very high (but it is also necessary). In weather forecast, by observing clouds, more fluid forces lead to the same appearance of clouds, so observing clouds is more "non-basic".

If a discipline finds its "first law", we can accurately predict the phenomenon in principle along the one-to-one causal logic chain. For example, only by finding the "first law"-the law of fluid mechanics can the accuracy of weather forecast be greatly improved. With the "first law", we can use computers to deal with the "first law" in different places and at different times, and combine the primary model with the empirical law to predict the future situation.

Now back to the problem of earthquake prediction, similar to the study of fluid mechanics in weather prediction, earthquake prediction deals with solid mechanics. The "first law" in the field of earthquake prediction is obviously the law of solid mechanics, specifically the deformation and stress of various solids. To truly and accurately predict earthquakes, we must know the solid composition and deformation everywhere. First, we must study clearly in the laboratory how much deformation of each solid will break and how much elastic energy will be released. It is also necessary to find out the attenuation law of these energies when they propagate in solids in different strata. Of course, because the stress on solid is far more complicated than that on fluid, even in the laboratory, only probabilistic results can be obtained, but it is also very helpful for earthquake prediction, because it establishes a one-to-one causal relationship. But once this probability is weak to a certain extent, the one-to-one causal chain will be greatly weakened. If physics proves that the probability p of the relationship between the deformation and fracture of solids is less than the probability of small probability events (0.3%), then the scientific value of the whole system of earthquake prediction is not great (but as long as the causal chain is not too weak, the prediction is meaningful, for example, predicting that there is a 5% possibility of an earthquake of magnitude 8 in a certain place, people can do some emergency measures, such as preparing food and water. However, if an earthquake of magnitude 8 of 0.0 1% is predicted, it will be considered as a small probability event in science. Therefore, I think studying the value of p is the key to solve whether earthquakes can be predicted or whether it is necessary to predict earthquakes in this century (but this is only a criterion in the classical and macro sense, and the micro and meso situations are different).

With the above understanding, the essence of various earthquake prediction methods is easy to see now. I think the only way to find out the composition and deformation of the earth's crust by means of seismic waves and geoelectricity and connect it with earthquakes is the one-to-one scientific method. Others, such as studying the recurrence period of earthquakes, studying the anomalies of terrestrial light, groundwater level and even animals (which involve not only geological factors but also biological factors, so the one-to-one correspondence is even worse), are all "non-basic laws". For earthquake phenomena, it is one-to-many and has low reliability. Of course, some successful primary models have good one-to-one characteristics (but it is impossible to be accurate to one-to-one), which is of great significance. For example, the theory of plate tectonics tells us that earthquakes generally occur at plate boundaries. In this way, we will focus on detecting the underground solid deformation at the plate boundary.

Compared with the weather forecast, I think today's earthquake forecast is still at a relatively primitive level: we have accumulated some empirical laws (such as the recurrence period, regional distribution and some abnormal phenomena before the earthquake) and relatively primary semi-quantitative models (such as plate tectonics and elastic wave rebound theory). ), but we don't have an accurate and overall grasp of the deformation and stress of underground solids, and there is no quantitative large-scale calculation and prediction. Moreover, due to the sudden earthquake phenomenon, large-scale earthquakes

In a word, the accuracy of earthquake prediction is extremely low at present, and the main work of Seismological Bureau is earthquake monitoring and evaluation.

Of course, the causal chain between the eye of the sky and the earthquake you mentioned is extremely weak and can be ignored.