Investigation of the seismicity after the initiation of a Seismic   Electric Signal activity until the main shock
  The behavior of seismicity in the area candidate to suffer a main shock is investigated after the observation of the Seismic Electric Signal activity until the impending mainshock. This makes use of the concept of natural time $\chi$ and reveals that the probability density function of the variance $\kappa_1(=< \chi^2 > -< \chi > ^2)$ exhibits distinct features before the occurrence of the mainshock. Examples are presented, which refer to magnitude class 6.0 earthquakes that occurred in Greece during the first two months in 2008. 
N. V. Sarlis, E. S. Skordas, M. S. Lazaridou, P. A. Varotsos