  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.
