Based on the continuous development of the technical system of airgun active source on land, the evolution process of seismic waves' physical parameters (wave velocity and vP/vS) can be presented in the form of meteorological cloud map by using the techniques of seismic tomography and computer image display, so as to achieve the purpose of "reading cloud maps and recognizing weather underground". On the basis of the results of "underground cloud maps", we can study the seismogenic process and mechanism of earthquakes, deeply understand the temporal and spatial evolution characteristics of seismic wave velocity and vP/vS in epicentral area before and after strong earthquakes, and also summarize and extract universal seismic precursor parameters and indicators. The results of the study have important scientific significance for further improving the efficiency of earthquake prediction.