EVALUATING THE STATISTICAL VALIDITY BEYOND CHANCE OF VAN EARTHQUAKE PRECURSORS

All predictions of the future can be to some extent successful by chance. This is a crucial issue mostly overlooked in assessing the validity of earthquake precursors. We analyse statistically the effectiveness of VAN predictions beyond chance by studying the complete list of predictions for the period 1987 January 1-1989 November 30 recently published by Varotsos & Lazaridou (1991) using any possible combination of the 'rules of the game' that they consider. We find that the apparent success of VAN predictions can be confidently ascribed to chance; conversely, we find that the occurrence of earthquakes with M(S) greater-than-or-equal-to 5.8 is followed by VAN predictions (with identical epicentre and magnitude) with a probability too large to be ascribed to chance.