Statistical analysis and clustering features of the Phlegraean Fields earthquake sequence (May 1983-May 1984)

Abstract The seismic activity at the Phlegraean Fields volcanic area (Southern Italy) during the period May 1983-May 1984 (5,301 selected events) has been analyzed from a statistical point of view. The analysis of the time series associated to the microearthquakes shows a high degree of interdependence among the events, the main feature being the occurrence of dense swarms. The Generalized Poisson Process provides a good fit for the sequence. The clustering of the events has not substantially changed during the analyzed period, while the mean rate of occurrence of the swarms has generally increased. The distribution of the magnitudes within the swarms shows pronounced maxima of energy around the center of the subsequences, in agreement with theoretical models of fractures in highly heterogeneous media.

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