Foreshock activity as a precursor of strong earthquakes in Corinthos Gulf,Central Greece

Foreshock activity preceding strong (M-s greater than or equal to 5) main s hocks in the Corinthos Gulf, Central Greece, is examined from primarily a d ata set of 1970-1998 and supplementary from data sets of 1785-1910 and 1911 -1969. It has been found that foreshock activity appears at time T less tha n or equal to 4 months before the main shock. In general there is no appare nt tendency of foreshock epicenters to move towards the main shock epicente r. The last 10 days of the foreshock period is the most important phase sin ce the probability for the main shock occurrence at any time within that ti me window is very high exceeding 0.83. The duration of the foreshock period as well as the largest foreshock magnitude are both independent of the mai n shock magnitude. Obtained results are important for inclusion in probabil istic earthquake predictions in the Corinthos Gulf. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.