Precursor candidacy and validation: The VAN case so far

A reliable identification of seismic precursors requires a two-step statistical approach: a retrospective "learning" step to establish the candidate precursors on the basis of ad hoc chosen laws of the game, and a "validation" step which evaluates candidate precursors on an independent data set according to the previously established laws of the game. No published work has so far provided a sound support to the candidacy of the VAN signals as earthquake precursors. The problem is complicated by a chronic fuzziness in the text of VAN's predictions, which often allows different interpretations, and by the absence of any clear statement by VAN of the laws of the game. Copyright 1996 by the American Geophysical Union.