Etna update, 02.06.2023

The weather at Mt Etna continued to be rather unsettled with many clouds and thunderstorms, which often hindered the observation of the summit craters via webcams during the last week. However, there were also clear periods, especially in the morning and evening hours. During my observations, I could no longer see any glow above Bocca Nuova. During the day, the usual intense and pulsating gas emission was observed. At the Southeast Crater complex, glow was temporarily visible in the early morning of 27 May. However, due to a cap of clouds it was only dimly visible and seemed to emanate from the northeastern summit area of New Southeast Crater. During the following nights I could not observe any more glow. During the day, gas and a lot of white steam rose both inside the large breach and in the entire summit area of New Southeast Crater. Due to high humidity, these emissions appeared quite imposing at times. I did not observe any significant gas emissions from Voragine and Northeast Crater.

The evaluation of the data from the GPS stations showed no significant deviations for the period between 22 and 28 May [1].
The signals from the Casa Bada clinometric station showed a deformation (inflation) of up to 2 microradians in connection with an earthquake that occurred in the Valle del Bove on 28 May and reached a magnitude of 4 [1].

The measurement of infrasound activity at the summit craters showed an increased number of events between 22 and 24 May. The source of the activity was the area of Bocca Nuova/Voragine. The southeast crater, on the other hand, played only a subordinate role. On the following days, strong winds hindered the measurements [1].

Sulphur dioxide emissions at the summit craters were at medium levels in the week from 22 to 28 May. Peak emission rates also reached high levels.
Ground carbon dioxide emissions (ETNAGAS station) continued to increase during the same period and were at medium levels [1].

The online seismograms of the ECNE station showed only very small and sporadic signals last week [2].
The tremor fluctuated between low and medium levels last week, then increased somewhat and stabilised at medium levels in the last few days [2].
The source of the tremor was located in the period from 22 to 28 May between the Central Crater and Bocca Nuova and fluctuated at an altitude between 1500 m and 2900 m above sea level. Towards the end of the measurement period, the source of the tremor shifted slightly eastwards to the eastern base of New Southeast Crater [1].

On 28.05. a pronounced series of earthquakes occurred on the eastern flank, in the greater Valle del Bove area (Monte Centenari - Monte Scorsone - Rifugio Citelli). The strongest tremor had a magnitude of 4.0. Several other quakes reached magnitudes of just over 2. The quakes occurred at a depth of approx. 4 - 6 km [3].

My interpretation of the data and speculations about further developments:
The striking series of earthquakes on 28 May was most likely caused by the rise of magma, as there was a slight change in the slope at the same time as the quakes. The still high measured values of soil carbon dioxide and the increased emission rates of sulphur dioxide at the summit craters also indicate that a batch of fresh magma has apparently arrived. It is therefore only a matter of time before new eruptive activity occurs on Etna. This could again lead to a paroxysm at the southeast crater complex, but longer-lasting strombolian and/or effusive activity are also possible. Most recently, the source of the tremor in the area of the eastern base of the New Southeast Crater had advanced relatively far to the surface. Could this area become the scene of new activity? Unfortunately, it is still very difficult to make forecasts and the old lady does what she wants anyway.

1 - INGV-Sezione di Catania. 2023.Etna - Bollettino settimanale, 22/05/2023 - 28/05/2023
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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