Long-Term Clustering, Scaling, and Universality in the Temporal Occurrence of Earthquakes

The probability densities of the earthquake recurrence times for different spatial areas and magnitude ranges were determined. It was shown that the ranges could be described by a unique universal distribution if the time was rescaled with the rate of seismic occurrence. The shape of the distribution was found to show the existence of clustering beyond the duration of aftershock bursts. It was also demonstrated that scaling revealed the self-similarity of the clustering structure in the space time magnitude domain.