With a new study of the seismic and dilatometric data of the eruptive crisis that occurred on Stromboli in the summer of 2019, anomalous variations have been highlighted that can contribute to the creation of an early warning system
A group of researchers from the National Institute of Geophysics and Volcanology (INGV) and from the Central Geofísico Observatory of the Instituto Geográfico Nacional (IGN, Spain) has subsequently studied the seismic data and the signals recorded by a well dilatometer installed on the Stromboli island. From the search results 'Geophysical precursors of the July-August 2019 paroxysmal eruptive phase and their implications for Stromboli volcano (Italy) monitoring', just published in Scientific Reports, variations of the volcanic system have been highlighted starting from about a month before the event of July 3, 2019.
In the analysis of the dilatometer data, by applying an appropriate algorithm for the recognition of transients in the time series, the researchers highlighted a variation of the signal 10 minutes before the paroxysm of July 3 and 7,5 minutes before the paroxysm of August 28, 2019.
“The conduit of the Stromboli volcano is occupied in the most superficial part by magma poor in gas and rich in crystals, in the deepest part, however, by magma rich in gas but poor in crystals. During normal Strombolian explosions, the superficial black magma is expelled, while the deeper magma fills the rising conduit”, explains Giovanni Macedonio, physicist at the INGV Vesuvius Observatory and co-author of the research.
“Magma rich in gas and poor in crystals is emitted during paroxysms. This is why it is generally recognized that paroxysmal explosions are triggered by the rapid ascent of this magma from an area 5-10 km deep. Its rapid ascent causes inflation and oscillation of the upper conduit.", continues the volcanologist of the INGV Etna Observatory Sonia Calvari, co-author of the study.
“The new parameters calculated from the seismic data recorded by our monitoring networks could, in the future, help to highlight phases of anomalous seismic activity which can precede paroxysmal activity by weeks. Furthermore, the algorithm applied for the analysis of the dilatometer data can help to realize an early warning system capable of giving a short-term warning before a paroxysmal explosion” concludes Flora Giudicepietro, volcanologist at the INGV Vesuvius Observatory and first author of the research.
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Figure 1 - Stromboli, summer 2019
Figure 2 - Signals of the SVO dilatometer recorded before the paroxysms of July 3 and August 28, 2019. The signal
relating to July 3 (top of the graph) is compared with the effusive phase that preceded the paroxysm,
recorded by cameras. a) marks the beginning of a strain increase (13:30:00 UTC); b) mark the first little ones
lava overflows (13:46 pm); c) indicates the opening of a small vent at the base of the NE crater, which feeds a thin
lava flow (14pm); d) indicates the moment in which the minimum strain is reached (00:30:14); e) marks the moment in
which the automatic algorithm we used detects the transient in the strain signal (14:35:44), 10 minutes before
of the explosion; f) small lava flow inside the crater (14:43:10); g) beginning of the paroxysmal explosion
(14:45:40). The images from the INGV camera in the upper part of the figure indicate the moments relating to
matching letters.