  We show that seismic waiting time distributions in California and Iceland
have many features in common as, for example, a power-law decay with exponent
$\alpha \approx 1.1$ for intermediate and with exponent $\gamma \approx 0.6$
for short waiting times. While the transition point between these two regimes
scales proportionally with the size of the considered area, the full
distribution is not universal and depends in a non-trivial way on the
geological area under consideration and its size. This is due to the spatial
distribution of epicenters which does \emph{not} form a simple mono-fractal.
Yet, the dependence of the waiting time distributions on the threshold
magnitude seems to be universal.
