Some characteristics of ring-shaped seismicity structures forming prior to large and great earthquakes

Shallow ring-shaped seismicity structures prior to 23 large and great earthquakes were picked out in different subduction zones. In many cases essential growth of the total energy of earthquakes, forming ring-shaped structures was observed directly prior to such events. The data on time duration intervals ΔТp, in which such effect takes place, were adduced for earthquakes with magnitudes from 7.0 to 9.1 in different subduction zones. We obtained a correlation dependence of ΔТp on magnitudes of large earthquakes, before which ring-shaped structures are forming. Big ring-shaped structure was picked out in the region of South Kamchatka. That gave a possibility to predict a preparation of great earthquake here. Using of the correlation dependence allows us to specify noticably expected time of such event. The data obtained can be used for a purpose of mid-term prognosis of large and great earthquakes.