Evaluation of extreme magnitudes of earthquakes using the method of Gumbel

The unique empirical materials on earthquakes in the Japanese region for the complete seismic cycle (116 years) and several seismic cycles (~1400 years) were used for testing the method applicability. It was shown that the third limiting Gumbel distribution method could be effectively used for the evaluation of Mmax at the following conditions: 1. the earthquakes catalogue must be unified by magnitude and contain, practically without omissions, all events from the given minimal level of magnitude, during the whole period of observations; 2. The used time interval must be commensurable with the seismic cycle duration. More stable estimations are obtained not for the limiting amplitudes but for the magnitudes at given distribution of probability function values. The Gumbel method, taking into account the above mentioned conditions, was used for the evaluation of Mmax in three zones of the Kurile-Okhotsk region. It has been obtained a good conformity of maximal magnitudes observed in the regions for 100 years, and the Mmax values, at the value of distribution of probability function PI = 0,995.