Complex Features in a Network of Worldwide Seismic Events

The understanding of long-distance relations between seismic activities has for long been of interest to seismologists and geologists. Despite all the existing knowledge about the production of seismic waves through slips on faults, much remains to be discovered regarding the dynamics responsible for these slips. A key step in deepening this knowledge is the study, analysis and modeling of the seismic distributions in space and time. In this paper we have used data from the world-wide earthquake catalog for the period between 1972 and 2011, to generate a network of sites around the world for earthquakes with magnitude $m \geq 4.5$ in the Richter scale. After the network construction, we have analyzed the results under two viewpoints. Firstly, in contrast to previous works, which have considered just small areas, we showed that the best fitting for networks of seismic events is not a pure power law, but a power law with exponential cutoff. We also have found that the global network presents small-world properties. Secondly, we have
found that the time intervals between successive earthquakes have a cumulative probability distribution well fitted by nontraditional functional forms. Our results reinforce the idea that the Earth is in a critical state and furthermore point towards temporal and spatial correlations between earthquakes in different places. We also sketch some future trends of our work.