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

Abstract

Foreshock activity preceding strong (Ms ≥ 5) main shocks in the Corinthos Gulf, Central Greece, is examined from primarily a data 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 ≤ 4 months before the main shock. In general there is no apparent tendency of foreshock epicenters to move towards the main shock epicenter. The last 10 days of the foreshock period is the most important phase since the probability for the main shock occurrence at any time within that time 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 main shock magnitude. Obtained results are important for inclusion in probabilistic earthquake predictions in the Corinthos Gulf.