Precursor phenomena or accompanying changes in seismic regime?

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On the basis of the analysis results of seismic regime parameter variability in the generalized vicinity of a
strong earthquake and of a number of seismic regime models the question on what are the so-called precursors
of strong earthquakes is discussed. It is possible, that precursors reflect some process which in its development
lead to the occurrence of a strong earthquake. But it is also possible, that such a process of strong earthquake
preparation does not exist, and a combination of precursors reflect distinctions in seismic regime, corresponding
to greater and smaller probability of a casual occurrence of a strong earthquake. The applied models of seismic
regime support both such interpretations. The substantial and not trivial forecasting of a strong earthquake is
possible in the both cases, but theoretically admissible accuracy of the prognosis is very different. The results
of the analysis of seismic regime parameter variability in the generalized vicinity of a strong earthquake can
be treated in terms of the both approaches. Nevertheless, the existence of the progressive increase of seismic
activity by the moment of a strong earthquake supports mostly the existence of the process of strong earthquake
preparation.