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Seismic and Infrasound Signals at Mt. Etna: Modelling the North-East Crater Conduit and its Relation with the 2008-2009 Eruption Feeding System
Author(s)
Language
English
Obiettivo Specifico
Status
Published
JCR Journal
JCR Journal
Title of the book
Issue/vol(year)
/254 (2013)
ISSN
0377-0273
Electronic ISSN
1872-6097
Publisher
Elsevier Science Limited
Pages (printed)
53-68
Issued date
2013
Abstract
On 13 May 2008, an eruption began at Mt. Etna from an eruptive fissure that opened on the upper
eastern flank of the volcano. During 12-13 May, 157 infrasonic events, together with the related
seismic transients, were collected. We carried out several analyses to obtain dominant frequencies,
pseudospectrograms, peak-to-peak amplitudes, source locations and time lags between infrasonic
and seismic events. Spectra of the infrasonic events show two main spectral peaks in the frequency
bands ~0.4-0.7 Hz and 1.5-2.0 Hz, respectively. Both infrasonic and seismic events were separately
located below the North-East Crater, where no eruptive activity was observed. Moreover,
significant changes in infrasound spectral content, as well as in the infrasonic-seismic lags, were
found a few hours before the beginning of the eruption. On the basis of the collected information
the infrasound source mechanism was modelled as a superposition of pipe and Helmholtz
resonance, also leading to outline the geometry of the shallower portion of the North-East Crater
plumbing system. The occurrence of these seismo-infrasonic events together with other geological
and geophysical evidences, led us to inferring a direct link between North-East Crater activity and
the eruptive fissure. Further, based on variations over time of both spectral features and seismicinfrasonic
time lag, shallowing phenomena of the free magma column inside North-East Crater
conduit were hypothesized. Such an uprise of magma was likely caused by a pressure increase
inside the plumbing system occurring before the beginning of the 2008-2009 eruption.
eastern flank of the volcano. During 12-13 May, 157 infrasonic events, together with the related
seismic transients, were collected. We carried out several analyses to obtain dominant frequencies,
pseudospectrograms, peak-to-peak amplitudes, source locations and time lags between infrasonic
and seismic events. Spectra of the infrasonic events show two main spectral peaks in the frequency
bands ~0.4-0.7 Hz and 1.5-2.0 Hz, respectively. Both infrasonic and seismic events were separately
located below the North-East Crater, where no eruptive activity was observed. Moreover,
significant changes in infrasound spectral content, as well as in the infrasonic-seismic lags, were
found a few hours before the beginning of the eruption. On the basis of the collected information
the infrasound source mechanism was modelled as a superposition of pipe and Helmholtz
resonance, also leading to outline the geometry of the shallower portion of the North-East Crater
plumbing system. The occurrence of these seismo-infrasonic events together with other geological
and geophysical evidences, led us to inferring a direct link between North-East Crater activity and
the eruptive fissure. Further, based on variations over time of both spectral features and seismicinfrasonic
time lag, shallowing phenomena of the free magma column inside North-East Crater
conduit were hypothesized. Such an uprise of magma was likely caused by a pressure increase
inside the plumbing system occurring before the beginning of the 2008-2009 eruption.
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