What is the main reason for the difficulty in earthquake prediction?

There are three difficulties in earthquake prediction:

One is the impenetrability of the earth's interior. Up to now, the deepest drilling is the ultra-deep drilling in kola peninsula, the former Soviet Union, which reaches 12km. Compared with the average radius of 6,370km on the earth, it is still "superficial" and still cannot solve the problem of direct observation of the earthquake source.

The description of earthquakes in academic circles still stays in the qualitative statement given by Li Siguang that "local underground energy will explode when it accumulates to a certain extent", but there is no quantitative statement. In other words, we don't know how much energy is needed to trigger an earthquake. The critical point of an earthquake is how much energy is gathered, which cannot be solved in a short time and has no theoretical support. Seismologists vividly compare this situation to the initial stage of understanding the earth. According to Chen Xuezhong, a researcher at the Institute of Earthquake Prediction, Seismological Bureau of China, what is the mechanism of earthquakes? We can't go underground to find out, just as heaven is easier to go underground.

The second is the infrequent occurrence of major earthquakes. Up to now, the research on precursory phenomena before large earthquakes is still in the stage of summarizing and studying various earthquake cases, lacking practical and reliable empirical laws necessary for establishing the theory of earthquake occurrence.

Thirdly, the complexity of seismic physical process. The earthquake process is a highly nonlinear and extremely complicated physical process. The complexity and variability of earthquake precursors may be closely related to the complexity of the geological environment in the source area and the high nonlinearity and complexity of the earthquake process.