During the first three months of 2009 a sequence of small shocks M ≤ 2.7 occurred near the city of L’Aquila. Towards the end of March the frequency of the shocks was rising and on March 30 an M = 4 earthquake occurred. A Committee of experts was charged to examine the likelihood of an impending strong earthquake. On March 31 the Committee concluded that nowadays no short-term prediction is possible and whatever proposed forecasting is not founded on a scientific basis. In this paper some critical comments are presented both on the content of this conclusion and on the method used by the Committee for the analysis. We observe that foreshocks are considered by the scientific community as a very real precursory phenomenon, even though with a high probability of false alarm. Statistical researches carried out in Italy and in California found that this probability is of the order of 0.98, so that the probability of a strong earthquake after the foreshock is of the order of 0.02. In absolute terms the risk is very small, however it is more than 100 times larger than the basic risk of the zone. As far as the method is concerned the analysis should take into account, besides all other possible seismolgical symptoms, also the social scenario in which the foreshock happens. Some results of theoretical researches on alarm systems based on more than one precursor are then summarized. They show how, starting from the characteristics of the precursors, it is possible to define new quantities that are helpful when the matter is to issue a public warning. It is a typical case of decision in uncertain conditions (small probabilities, heavy possible damage) in which an important role is played by social repercussions.
