Estimating the expected seismicity rates of volcano-tectonic earthquakes at Mt. Etna (italy) by a geometric kinematic approach

Abstract

Seismic hazard studies have been undertaken at Etna volcano in the last years with the aim of estimating the potential of local fault’s activity in generating destructive earthquakes. The target is the mid-term assessment (30, 20, 10 and 5 yrs), as the identification of zones that are exposed to the recurrent seismic shaking may be important for land planning at a local scale, and it represents a valuable complement to establish priority criteria for seismic risk reduction action. The methodologies applied at Mt. Etna area include probabilistic approaches based on the use of historical macroseismic data (the “site approach” by the software code SASHA, see Azzaro et al., 2008) and fault-based time-dependent models in which occurrence probabilities of major earthquakes are estimated through the Brownian Passage Time (BPT) function and the time lapsed since the last event (Azzaro et al., 2012b, 2013b). Mean return period of major earthquakes - strong to destructive events with epicentral intensity I0 ≥ VIII EMS, considered as “proxies” of “characteristic” earthquakes – have been obtained by the fault seismic histories, i.e. the associations “earthquake-seismogenic fault” derived from the historical catalogue of Etnean earthquakes (CMTE Working Group, 2014). Inter-time statistics of major earthquakes have been applied to the Timpe tectonic system, considered as a homogeneous seismotectonic domain (Azzaro et al., 2013b), obtaining a mean recurrence time (Tmean) of 71.3 years, and an aperiodicity factor α (σTmean/Tmean) = 0.42, typical of semi-periodic processes. In the present study we present the preliminary results of an analysis aimed at verifying the variability of the mean occurrence times of major earthquakes generated by the main tectonic systems at Etna (Pernicana and Timpe faults) by using a geological approach based on geometrickinematic parameters (3D dimensions, slip-rates etc) representative of fault activity. Method and input data.