Etna update, 30.06.2023

During the last week, clouds temporarily hindered the observation of the summit craters via webcams. During the cloud-free hours, the usual gas emissions appeared, which continued to be most intense at Bocca Nuova and at times also intensified like pulses. At the southeast crater complex, gas was emitted persistently from the central area between the old and new southeast crater. The upper northeast to north flank of New Southeast Crater also emitted gas or white steam persistently. At Voragine and Northeast Crater I could still hardly observe any gas emission.

The analysis of the data from the GPS stations showed no significant changes for the period between 19 and 25 June [1].
The signals from the clinometric stations showed no significant changes for the period between 19 and 25 June [1].

The measurement of infrasound activity at the summit craters showed a low number of events between 19 and 25 June. The amplitude of the events was predominantly weak and the source of the events was located in Bocca Nuova [1].

Sulphur dioxide emissions at the summit craters remained at medium levels during the week of 19-25 June.
Ground carbon dioxide emissions (ETNAGAS station) decreased slightly during the same period, but still remained at a high average level.
The concentration of helium isotopes (3He/4He - ratio) in the Etna area, which was last determined on 21 June, was slightly higher than in the last measurements with a value of 0.63. The measured value was at a high level. The measured value was at a high level [1].

The online seismograms of the ECNE station showed weak noise last week, as well as some occasional weak signals.
The tremor was at a medium level last week and was subject to only minor fluctuations. Overall, there was a slightly increasing trend [2].
In the period from 19 to 25 June, the source of the tremor was below the southeast crater at a depth between 2000 - and 2800 m [1].

On 23 June, an earthquake of magnitude 1.5 occurred near Milo (eastern flank). Between 24 and 25 June, several weak earthquakes occurred in the area of Monte Fontane (eastern flank), the strongest reaching a magnitude of 1.9. From 27 to 30 June, a series of earthquakes occurred in the Fleri - Zafferana Etnea - Santa Venerina - Milo area (eastern flank). The strongest earthquake reached a magnitude of 3.1, but most of the quakes were much weaker and had magnitudes below 2.0. The depth of the quakes varied between 2 and 12 km [3].

My interpretation of the data and speculations about the further development:
The recent series of earthquakes in the Zafferana - Santa Venerina area was, in my opinion, most likely caused by a fault that extends along the eastern flank of Etna from north to south. The quakes that occur there are tectonic in nature, but the stresses that are discharged are often caused by magma movements under the mountain. Thus, this series of earthquakes could be an indication of rising magma or inflation caused by it. The still high ground carbon dioxide emissions also point to rising magma. Another indication that fresh magma continues to flow in under the mountain is the still high 3He/4He ratio.
Unfortunately, it is difficult to predict when this magma will reach the surface. This could be in a few hours, but also in a few weeks. Anything from a paroxysmal eruption to a purely effusive eruption is possible, as has been shown again in recent months. The most likely location for an eruption is probably the southeast crater complex.
At present, there are no indications of an imminent eruption.

1. INGV-Sezione di Catania. 2023. Etna - Bollettino settimanale, 19/06/2023 - 25/06/2023
2. INGV-Sezione di Catania. 2023. Home. TREMORE VULCANICO. ECNE
3. INGV. Osservatorio Etneo. Sorveglianza e Monitoraggio. DATABASE TERREMOTI. Localizzazioni di sala operativa. 2023

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