Seismoacoustic investigations of paroxysmal activity at Mt. Etna volcano: New insights into the 16 November 2006 eruption

On 16 November 2006, a 1 day long paroxysmal eruption occurred at the summit
craters of Mt. Etna volcano. A multiparametric approach, consisting of analyzing
infrasonic, seismic, and video camera recordings, was carried out to follow its evolution.
Volcanological and geophysical observations identified three eruptive phases. In the first
phase, infrasonic and seismic characteristics reflected the highly explosive nature of the
activity. Waveform characterization of infrasound events confirmed the activity of the
several explosive vents at the summit of Southeast Crater (SEC). During the second phase,
results highlighted the decoupling between seismic and infrasonic sources, which was
due to the decrease in explosive activity and the reactivation of effusive vents located
south of Bocca Nuova and on the saddle between Bocca Nuova and SEC. The third phase
was the most intense and was characterized by various volcanic phenomena (pyroclastic
flows, jets of dark ash, and white steam). The very high radiated infrasonic energy,
together with infrasound event features, led us to infer a gas enrichment of the shallow
magma column, preceding by a few minutes and likely related to the pyroclastic flows in
the SEC area. After the eruption at SEC, variations in infrasound events related to the
activity of Northeast Crater (NEC) were found. The observed spectral changes and the
source mechanism modeling of the NEC infrasound events suggest the existence of a link
in the plumbing system feeding the two craters.