An alternative view of the Bayesian probabilistic prediction of strong shocks in the Hellenic Arc

Abstract

A Bayesian discrete distribution, as developed by Ferraes (1985), is applied to predict the inter-arrival times for strong shocks in the Hellenic Arc on the basis of nine samples of shocks with seismotectonic locations very different from those used by Ferraes. The results suggest an alternative view of the Bayesian probabilistic prediction of strong earthquakes in the Hellenic Arc, and can be summed up as follows: 1. (a) Maximum final Bayesian probabilities of various inter-arrival times in a given seismotectonic segment are very dependent on the data set used and particularly on its time length. 2. (b) When using this method to determine the time intervals during which large shocks are to be expected in the Western and Eastern Hellenic arcs, it is very difficult to estimate intervals of less than a decade. The determination of the occurrence time, even in the long-term sense, remains the major problem in the prediction of these shocks. 3. (c) Bayesian probabilities in conjunction with seismicity observations indicate that large intermediate depth earthquakes in the Hellenic Arc are long overdue. Shocks of this sort can be expected to occur in the next few years. It is also pointed out that although Bayesian-type predictions may be useful for engineering purposes, they are not a suitable basis for making specific predictions or taking special precautions.