Abstract
We investigated the possibility of forecasting the aftershock activities of large earthquakes occurring in and near the Japanese Islands. On the basis of the Modified Omori formula and the Gutenberg-Richter relation, an intensity function of aftershock occurrence, which contains four parameters, is obtained. We evaluated those four parameters for each aftershock sequence of 47 earthquakes which occurred in the period 1969 through 1990. Then, taking the mean values of the four parameters, and assuming that the aftershock sequence is a non-stationary Poisson process, we calculated the probabilities of the average aftershock occurrence for earthquakes in and near the Japanese Islands. It is shown that the coincidence between the forecasted and the actually observed aftershock activities are fairly well. It is expected that we can further improve the accuracy of forecasting by taking into consideration the regional differences of the four parameters contained in the intensity function of aftershock occurrence.
