Characterization of seismicity at Mt. Etna volcano (Italy) by inter-event time distribution

• Published in: Journal of volcanology and geothermal research 2014-01, Vol.270, p.1-9
• Main Authors: Sicali, Simona, Barbano, M. Serafina, D'Amico, Salvatore, Azzaro, Raffaele
• Format: Article
• Language: English
• Subjects: Crystalline rocks; Earth sciences; Earth, ocean, space; Earthquakes; Etna; Exact sciences and technology; Geothermal; Igneous and metamorphic rocks petrology, volcanic processes, magmas; Inter-event time; Occurrence pattern; Probability distribution functions; Regional tectonics; Seismic phenomena; Seismicity; Sicily; Volcano dynamics; Volcanoes; Volcanology
• ISSN: 0377-0273; 1872-6097
• DOI: 10.1016/j.jvolgeores.2013.11.011

The space–time inter-event time (IET) distributions of earthquakes occurring from 1988 to 2011 at Mt. Etna are analysed in order to identify the periodicity or stationary behaviour of seismicity, and to correlate it with the volcano-tectonic features of the region. The comparison between IET distributions at Etna with those obtained both for Sicily and Italy, shows that IETs at a larger scale are well-modelled by a gamma distribution, whereas at Etna local scale they are characterised by a bimodal curve, in which the two peaks are related to: (i) the contribution of local seismic swarms with very short inter-event times, and (ii) the background regional stationary seismicity. IET analysis is an important tool to investigate the behaviour of seismicity at different crustal levels in the Etna region, distinguishing sectors that are influenced by volcano dynamics or regional tectonics. Indeed, the spatial variation of IET distributions, obtained by analysing different Etna crustal sectors, shows that seismicity shallower than 5km is almost entirely characterised by short inter-event times and is mainly confined to the summit area. For earthquakes deeper than 5km occurring in the eastern flank of the volcano, as well as in eastern Sicily, IET distributions are characterised by independent events which suggest that both areas are influenced by the same extensional regional regime. By contrast, IET distributions obtained for the western flank and north-western Sicily are marked by two peaks, indicating that the compressional stress is acting in both areas. •Mt. Etna inter-event times (IETs) allow separating volcanic from tectonic seismicity.•The temporal occurrence of earthquakes reflects the influence of different stresses.•Short IETs due to magma intrusions coexist with background regional seismicity.•IETs in some sectors of Etna correlate with surrounding tectonic processes.•Mt. Etna is located between sectors affected by different regional stress fields.