#Etna update:
On 15 November 2022, Etna experienced a significant uplift in the summit area, which was accompanied by strong fluctuations of the tremor, as well as some weak earthquakes. However, there was no eruptive activity or other visible events.
In the past 14 days, gas emissions at Etna's summit craters continued to be concentrated at Bocca Nuova, where there was vigorous and pulse-like gas release.
At the Southeast Crater complex, some gas was persistently emitted from the breach or the central crater area. Some gas was also persistently emitted from the northern summit area of New Southeast Crater. A hot spot on the inner western crater wall of the breach was visible as a small glowing spot during the nights.
At Voragine and Northeast Crater, the webcams continued to show little significant gas release.
As reported by INGV, a significant change in the clinometric readings occurred in the early morning of 15 November. The first change occurred between 01:00 and 01:30 and the second between 03:50 and 04:30. In total, there was a change in the slope of almost one microradian, indicating an uplift that occurred in the area of the summit. At the same time, the DRUV station on Monte Ruvolo (western flank) showed significant variations in dilatometric data. No changes occurred after 05:00 [1].
The online seismograms of station ECNE were characterised by persistent noise during the phases of increased tremor, which wiped out most of the other signals. Otherwise, long-period signals appeared regularly.
The tremor decreased somewhat from 06/11 and then fluctuated at a medium level. On 14/11 there was a rapid increase to a high level, before the tremor temporarily dropped rapidly to a low level on 15/11. It then rose rapidly in the evening of this day, just reaching high level and staying there for a few hours. On 16/11 tremor declined with fluctuations and stabilised at a medium level [2].
In the evening of 15/11 the source of the tremor was located below Bocca Nuova at an altitude of about 3000 m [1].
On 07/11 two earthquakes occurred west of Bronte (northwest flank), reaching magnitudes of 1.7 and 1.9, respectively. On 12/11 a quake of magnitude 1.6 occurred in Piano Pernicana (northeast flank). On 12/11 a quake of magnitude 1.7 was registered southeast of Paternò (south west flank). On 15/11 several very weak (magnitude less than 1.5) quakes occurred in the area of the Southeast Crater complex. On 15th and 16th November two quakes occurred in Piano Pernicana with magnitudes of 1.5 and 2.0, respectively [3].
My interpretation of the data and speculations about the further development:
Probably a larger amount of magma temporarily rose on 15th November, as the clinometric data showed a rapid and significant change in the slope of the mountain flank in the early morning of that day. In addition, several weak earthquakes occurred simultaneously at the Southeast Crater complex. Afterwards, the tremor, which had been elevated for months before, dropped significantly. Since there was no eruptive activity, it can be assumed that the rising magma was stored inside the mountain. It probably spread along the rift zones. At least the Pernicana fault on the northeast flank reacted to the changes in the mountain with some weak earthquakes. It is therefore conceivable that the magma migrated north/northeast from the Southeast Crater complex towards the northeast rift zone. After a temporary strong and rapid increase of the tremor, it has levelled off again at a medium level. The situation has thus returned to normal since 16 November. It is quite possible that the event of 15 November is the prelude to further similar events. Therefore, in my opinion, the probability of the return of eruptive activity within the next few weeks, especially at the Southeast Crater complex, has increased significantly.
Sources:
1 - INGV-Sezione di Catania. 2022. Comunicati attività vulcanica. 15/11/2022 19:47 - COMUNICATO ETNA
2 - INGV-Sezione di Catania. 2022. Home. TREMORE VULCANICO. ECNE
3 - INGV. Osservatorio Etneo. Sorveglianza e Monitoraggio. DATABASE TERREMOTI. Localizzazioni di sala operativa. 2022.
