Moment magnitude for earthquakes in the Etna volcano area

Accurate quantification of seismic activity in volcanic regions is an important asset for im- proving hazard and risk assessment. This is especially true for densely populated areas, as in the case of Etna volcano (Southern Italy). There, the volcanic hazard is amplified by the seismic risk of active faults, especially on the eastern flank of the volcano. In such a context, it is common to rely on moment magnitude (MW) to characterize seismicity and monitor the energy released during an eruption. In this study, we calculate the moment-based magnitude (MW) for selected seismic data sets, using different approaches in distinct magnitude ranges to cover the widest possible range of magnitude that characterizes Etna’s seismicity. Specifically, we computed the MW from a data set of moment tensor solutions of earthquakes that occurred in the magnitude range 3.4 ≤ ML ≤ 4.8 during 2005–2020; we created a data set of seismic moment and associated MW for earthquakes 1.0 ≤ ML < 3.4 obtained by analysing source spectra; we fine-tuned two relationships, for shallow and deep earthquakes, to obtain MW from response spectra. Finally, we calibrated a specific relationship between MW and ML for the Etna area earthquakes in the range 1.0 ≤ ML ≤ 4.8. All the empirical relationships obtained in this study can be applied in real-time analysis of the seismicity to provide fast and robust information on the released seismic energy.