This work was carried out within the 2015 ART-IT project (Early Earthquake Alert in ITaly). Its main purpose is to investigate the performance and the critical issues of an early warning system with particular reference to the PRESTo system (PRobabilistic and Evolutionary early warning SysTem, [Iannacone et al., 2010; Satriano et al., 2011]) whose use has been tested in the framework of the above mentioned project. The correct operation of an early warning system can effectively guarantee a more effective management of a seismic emergency from the first seconds after the occurrence of a strong earthquake, allowing quick actions to reduce exposure and seismic risk. The work was substantially subdivided into two main steps. A first calibration phase, carried out in the first part of the...