  This paper presents an explanation of a possible mechanism underlying the
shape of the universal curve of Scaling Law for Earthquake Recurrence Time
Distributions. The presented simple stochastic cellular automaton model is
reproducing the gamma distribution fit with the proper value of the parameter
$\gamma$ characterizing Earth's seismicity and also imitates a deviation from
the fit at the short interevent times, as observed in real data.
  Thus the model suggests an explanation of the universal pattern of rescaled
Earthquake Recurrence Time Distributions in terms of combinatorial rules for
accumulation and abrupt release of seismic energy.
