Statistical significance of the precursory minima of the order parameter fluctuations of seismicity by modern methods of Statistical Physics

An order parameter for seismicity was introduced in the frame of natural time analysis [1]. Recent studies of the fluctuations of this order parameter revealed the existence of minima preceding major earthquakes [2-7]. Here, we review the statistical significance of these minima by using recent methods of Statistical Physics, such as receiver operating characteristics [8] and event coincidence analysis [9,10]. These methods are also applied to the investigation [11] of the statistical significance of Seismic Electric Signals [12].