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.