Spatial variability of the time-correlated behaviour in Italian seismicity

Using the National Institute of Geophysics and Volcanology seismic catalogue, an analysis of the time-clustering behaviour of the instrumental seismicity of Italy was performed. The time span of the analysed catalogue is from 1986 to 2001, and only the events with magnitude M≥2.4 were considered. The analysis, carried out on the full and aftershock-depleted catalogues, was performed using detrended fluctuation analysis, which permits the identification of correlated temporal structures in time series, even in the presence of trends or non-stationarities. Our findings confirm the presence of long-range behaviour in the temporal distribution of seismicity data of both full and depleted catalogues, suggesting that the clustering phenomenon is not due only to the generation of aftershocks following the occurrence of large shocks, but relies on the underlying time structure of the seismicity of Italian areas.