  The procedure by means of which the occurrence time of an impending mainshock
can be identified by analyzing in natural time the seismicity in the candidate
area subsequent to the recording of a precursory Seismic Electric Signals (SES)
activity is reviewed. Here, we report the application of this procedure to an
Mw5.4 mainshock that occurred in Greece on 17 November 2014 and was strongly
felt in Athens. This mainshock (which is pretty rare since it is the strongest
in that area for more than half a century) was preceded by an SES activity
recorded on 27 July 2014 and the results of the natural time analysis reveal
that the system approached the critical point (mainshock occurrence) early in
the morning on 15 November 2014. SES activities that have been recently
recorded are also presented. Furthermore, in a Note we discuss the case of the
Mw5.3 earthquake that was also strongly felt in Athens on 19 July 2019
(Parnitha fault).
