Earthquake forecasting in Italy.

Even if the deterministic prediction of earthquakes is presently not feasible and perhaps it will never be, several methods of probabilistic operational forecasting have been proposed in the last decades. Many of such methods take advantage of the well-known property of earthquakes to cluster in space and time. In order to verify the method, a testable hypothesis must be formulated based on a retrospective analysis but the real verification can only be made prospectively, based on data that will occur only after the final definition of the hypothesis. Any successive modification of the forecasting hypothesis will require a restart of the prospective test. The formulation and the testing require an earthquake catalog as most complete and homogenous as possible, particularly regarding the magnitude of events. This can be obtained by a careful calibration of available magnitude data.