  We study the seismicity (global seismic activity) that occurred in Greece
between 1976 and 2009 based on the dataset reported in Makropoulos et al.,
2012, using concepts of Non-extensive Statistical Physics. By considering the
entire and declustered datasets, for which the aftershocks have been removed,
we initially investigate the frequency-magnitude distribution and find that
both datasets are well approximated by a physical model derived in the
framework of Non-extensive Statistical Physics. We then carry out a study of
the distribution of interevent times of seismic events for different magnitude
thresholds and discover that the data are well approximated by a statistical
distribution of the $q$-exponential type that allows us to compute analytically
the hazard function of earthquake production. Our analysis thus reveals further
evidence that the underlying dynamical process of earthquake birth reflects a
kind of nonlinear memory due to long-term persistence of seismic events.
