ANOMALOUS VARIATIONS OF THE ENERGY E BEFORE LARGE AND MODERATE EARTHQUAKES

In this paper, the characteristics of temporal and spatial distribution of the energy E before twenty large and moderate earthquakes occurred in different regions are studied. The results show that in the vicinity of the epicenters of twelve earthquakes, there appear areas with high energy and with low energy outside them. Around the epicenters of the other eight earthquakes, areas show low energy only. The radii of such areas tend to increase with the magnitudes of the main shocks and an empirical relation between radii and magnitudes of the main shocks can be found. If low energy areas are assumed to be the parts of the earth crust in which the earthquake sources are under development, then the size of these areas for various magnitudes of earthquakes may be determined. It is -found also that as for variation of energy E with time, a period of low energy usually appears before the main shock. The time duration of low energy or the total anomalous time seems to be related to the magnitude. This feature seems to correspond to the case of a period of peak b-value before the main shock. Using such facts it might be possible to foretell the place, time and magnitude of an impending earthquake. The total normalized frequency No and the greatest magnitude ,M vary in the same way as the energy E, therefore the values of E, No and M as well as the b-value may all be possible earthquake precursors.