総合報告: 地震活動パターンと大地震の長期予測 -繰返し・空白域・静穏化・先行地震・移動・相関など-

Abstract

Recent studies (1987 and later) of seismicity patterns presumably having some power to predict large earthquakes are reviewed. Here ‘large earthquakes’ mean relatively large earthquakes considered as objects of prediction. Seismic gaps (observed in the later half of the recurrence cycle) are useful in limited fault segments. Many examples of seismic quiescence (local or regional) have been reported, some of which were followed by large earthquakes and others were not. Migration patterns of seismic activity are very variable and mostly transient. There are some cases of close correlation between large earthquakes in two regions. The test of the statistical significance of a proposed pattern is often difficult due to uncertainty in evaluating the effect of selection of favorable data set. However, many of the patterns seem to be real and can be used in the long-term probabilistic prediction of large earthquakes. The probability of occurrence of a large earthquake after the appearance of one of the patterns discussed here is not easy to estimate. This is because of (1) many parameters which characterize the pattern and the target earthquake, (2) regional differences in the character of pattern, and (3) relatively few observational data on each pattern in each region.