Seismic vs. geodetic moments at Mt. Etna volcano: a tool for a rapid understanding the eruptive behaviour?

The seismic to geodetic moment ratio (Mo/MG) related to seven magma intrusion episodes, occurring at Mt. Etna volcano between 1981 and 2008, are considered. The lateral eruptions show a moment ratio of 0.04–0.06; meaning that only about 5% of the stress energy accumulated with ground deformation was released by earthquakes. Significantly higher values instead characterized vertical (0.25–0.50) and non-eruptive (0.17) dike intrusions. This paper proposes a simple relationship, in order to estimate, during the early phases of an eruption, the intruding magma volumes by the cumulative seismic moment (of the ongoing seismicity) and elapsed time.