Space-time distribution of small earthquakes at Phlegraean Fields, south-central Italy

Abstract

A preliminary statistical analysis of the space-time distribution of small seismic events in the volcanic area of Phlegraean Fields, south-central Italy, was done on the basis of a catalogue of earthquakes recorded by the local seismic stations in the period January 1, December 31, 1983. The non-random character of the sequence has been tested by matching the observed time-dstribution of seismic events with the theoretical Poisson process. A clustered occurrence of seismic events seems to be the main cause of the departure from a Poisson process as the inter-arrival times distribution clearly shows. Furthermore, the non-random behaviour of the events space-time distribution mainly due to quiescient and clustered recursive seismic phases could be studied by using the method proposed byVon Seggern et al. (1981). The analysis and the space-time diagrams confirm the swarm-type character of the entire seismic sequence.