A QUANTITATIVE STUDY OF SOME AFTERSHOCK SEQUENCES IN GREECE

Temporal features of the aftershock activities following twelve modera te shallow earthquakes in Greece have been studied quantitatively, by making use of the modified Omori's formula and Akaike's Information Cr iterion (AIC). Although the earthquake sequences occurred in different seismotectonic regions in Greece, similar seismic patterns before the occurrence of large aftershocks have been observed. Aftershock activi ty shows an appreciable decrease from the level expected from the modi fied Omori formula before the occurrence of the large aftershock. Also in some cases, the aftershock activity recovers to a normal level or increases beyond it prior to the occurrence of the large aftershock, i f the aftershock activity is monitored immediately after the occurrenc e of the main shock. In such case, the observed pattern may be useful in predicting a large aftershock.