Time clustering properties of seismicity in the Etna region between 1874-1913

Time properties of seismic activity of the Etna Volcano (Italy) from 1874 to 1913, are investigated by fractal dimension analysis. Period selection was due to the interesting volcanic and seismic activity which had occurred within this time interval. A catalogue was adopted, revised by the reexamination of historical sources and with the addition of new material. Time evolution of the temporal fractal dimension Dt , calculated on a 40 seismic events moving window, revealed the following correlations with the eruptive processes: long term fractal dimension variations are due to the magma rise from the depth; mid term variations are closely related to stress conditions at the volcano edifice, and short term variations are induced by the onset of eruption. The spatial localisation of data allowed interpretation of seismic activity in relation to the main structural systems outcropping on the volcano edifice and in the surrounding areas