Abstract: Using the method of the natural perpendicular function development in this paper, the time facture variations and features of the energy field of the seismic activity in the regions around the epicenters before 30 earthquakes of M≥6.0 occureed in the main continent have been discussed. The results have indicated that before these large earthquakes, the time factors of the typical fields corresponding to several key eigenvalues all appear very evident abrupt rising or abrupt depressing variations, showing better corresponding relation with the future strong earthquakes. The time factor anomalies appear 1～3 years before the main shocks, less than 2 years in most cases, indicating the medium-short features of the anomalies. And the time factor anomalies appear less than 3 months before some earthquakes, indicating the impending features of the anomalies. We think that time factures of the seismic energy field are probably a kind of effective anomaly observation measure and the medium-short anomaly index before strong earthquakes.

Key words: Energy field, Natural perpendicular function development, Time factor anomaly, Earthquake prediction