The two behaviours of Mt. Etna volcano before and after a large intrusive episode: evidences from b value and fractal dimension of seismicity.

Seismic activity of Mt. Etna volcano has been investigated by analysing tim e-spatial fractal dimensions and the b value of the Gutenberg-Richter's law relatively to two differing eruptive style periods, i.e. 1983-1988 and 199 3-1996. The obtained results evidence two different volcano stress conditio ns before and after the large intrusive episode occurred during the time sp an 1989-1992. Fractal dimensions and the b value seem to be a promising too l to understand the internal current state of the volcano, allowing to eval uate the short-middle term volcanic hazard.