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Mount Etna (Sicilia, Italy) is one of the most active volcanoes worldwide, located at the boundary between the African and the Eurasian plates. It is characterized by the occurrence of many phenomena such as lava flows, ash eruptions, earthquakes. Its eastern flank is also characterized by a complex system of active faults, associated with an eastward flank movement, up until the submarine environment. As Etna flanks are densely inhabited areas, we aim at better understanding the link between these phenomena to better assess associated hazards and risks.Since 2018, we have been measuring several locations with Distributed Fiber Optic Sensing yearly, enabling us to observe strain at meter-scale spatial interval and on a broad frequency range. We show records and present results from selected cables. Close to the summit active craters, we interrogate dedicated cables, and could analyze the ground response in association with explosions and volcanic tremor. In urban areas, we interrogate telecommunication cables and record local earthquakes. In the submarine area, we interrogate a cable which crosses the North Alfeo fault with several different optical techniques. In the southern flank of the volcano, we show volcanic signals from a cable deployed in a borehole. We also demonstrate how simultaneous multi-fiber measurements can help constrain earthquake hypocenter location. We discuss opportunities and challenges of using fiber optic cable in various environments such as the Etna volcano and beyond, for an integrated vision from deep processes, their interaction with the sub-surface dynamics and the volcano-tectonic structures., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Timely estimations of volumes erupted during an eruption or a sequence of explosive events is of vital importance for investigating the eruptive activity and evaluating the associated hazard. A reliable method for estimating erupted volumes is based on the analysis of different digital surface models (DSMs) that nowadays can be obtained as often as required, and with sufficient accuracy, using stereo optical satellite imagery. At Etna, during 2011-2013, 44 lava fountains occurred emitting a total volume of over 100×106m3, as well as in 2020-2022 with over 60 events. Even if lava fountains produce limited deformation, effects, their high temporal frequency can produce large cumulative volumes. While thermal satellite imagery can provide estimates of lava volume, the real time estimation of the total deposits is still an open challenge. High precision strain recorded by borehole dilatometer (precision of order of 10-10) is able to detect the effects of the source that feeds the lava fountain. The recorded changes in real-time are proportional to the volume variation of the source that empties feeding the eruption, and are therefore proportional to the total erupted volume. Here we use the volumes derived from multiple DSMs comparison to calibrate the volumes obtained from strain changes. The validation is performed by using the plenty of high spatial resolution satellite images and strain records available at Etna during 2020-2022. We show how this new approach can provide robust information on the erupted volumes both over time and in real-time through the strain recorded by continuous monitoring., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

“1-month seismological experiment on Etna, Italy in 2019" is a 1-month seismological experi-ment realized near the Pizzi Deneri Observatory on Etna, Italy, by Eva Eibl and Daniel Vollmer (University of Potsdam) in collaboration with Philippe Jousset from GFZ Potsdam Germany and Gilda Currenti and Graziano Larocca from INGV-OE, Italy. From August to September 2019, we recorded the volcano-seismic events accompanying the volcanic activity using a rotational sensor and a co-located seismometer. The aim of the seismological experiment was to study LP events, VT events and tremor. We used a 3-component broadband seismometer (Nanometrics Trillium Compact 120 s) and a 3-component rotational sensor (iXblue blueSeis-3A) and stored the data on a DataCube and CommunicationCube, respectively. Sensors were installed on the same 35 * 35 * 3 cm3 granitic base plate at about 40 cm depth enclosed by backfilled pyroclastic material to avoid wind noise. The instruments recorded at 200 Hz sampling rate and were located about 2 km from the craters on Etna. The setup was powered using 3 solar panels of 140W each and three batteries of 75Ah each. We oriented the rotational sensor and seismometer using a Quadrans fiber-optical gyrocompass. The Quadrans is not affected by magnetic minerals in the ground and our sensors are hence properly aligned to geographic north. We converted the seismometer data to MSEED using Pyrocko’s Jackseis program and created a catalogs of LP events and VT events that were further investigated in Eibl et al. 2022. Waveform data are available from the GEOFON data centre, under network code ZR.

Understanding physical processes prior and during eruptions remains challenging, due to uncertainties about subsurface structures and undetected processes within the volcano. Here, the authors use a dedicated fibre-optic cable to obtain strain data and identify volcanic events and image hidden near-surface volcanic structural features at Etna volcano, Italy. In the paper Jousset et al. (2022), we detect and characterize strain signals associated with explosions, and we find evidences for non-linear grain interactions in a scoria layer of spatially variable thickness. We also demonstrate that wavefield separation allows us to incrementally investigate the ground response to various excitation mechanisms, and we identify very small volcanic events, which we relate to fluid migration and degassing. We recorded seismic signals from natural and man-made sources with 2-m spacing along a 1.5-km-long fibre-optic cable layout near the summit of actives craters of Etna volcano, Italy. Those results provide the basis for improved volcano monitoring and hazard assessment using DAS. This data publication contains the full data set used for the analysis. This data set comprises strain-rate data from 1 iDAS interrogator (~750 traces), velocity data from 15 geophones and 4 broadband seismometers, and infrasonic pressure data from infrasound sensors. For further explanation of the data and related processing steps, please refer to Jousset et al. (2022).

The Campi Flegrei geothermal system sets in one of the most famous and hazardous volcanic caldera in the world. The geothermal dynamics is suspected to have a crucial role in the monitored unrest phases and in the eruption triggering as well. Numerical models in the literature do not properly consider the geochemical effects of fluid-rock interaction into the hydrothermal circulation and this gap limits the wholly understanding of the dynamics. This paper focuses on fluid-rock interaction effects at the Campi Flegrei and presents relevant information requested for reactive transport simulations. In particular, we provide: (1) an extensive review of available data and new petrographic analyses of the San Vito cores rearranged in a conceptual model useful to define representative geochemical and petrophysical parameters of rock formations suitable for numerical simulations and (2) the implemented thermodynamic and kinetic data set calibrated for the San Vito 1 well area, central in the geothermal reservoir. A preliminary 0D-geochemical model, performed with a different contribution of CO2 at high (165 °C) and low (85 °C) temperatures, firstly allows reproducing the hydrothermal reactions over time of the Campanian Ignimbrite formation, the most important deposits in the case study area.

Volcanic and seismic activities produce a variety of phenomena that put population at risk. In order to assess the seismic and volcanic hazard, many instruments are deployed around active volcanoes and seismic fault zones. Their records are useful to observe the activity of the volcanoes and faults in order to understand better their behaviour and issue warnings to authorities in charge of the public security. In this study, we used optical cables around Etna volcano to observe seismic and pressure signals associated with volcanic activity. The 2018 expedition consisted of three experiments. Firstly, we used a 4-km long telecom line in Zafferana and recorded all geodynamic and other activities for about 20 days. At this site, the fibre is known to cross active faults that are linked to the eastern volcano flank slowly sliding towards the sea. Secondly, we tested a 40 km-long cable from an internet provider at the western side of the volcano. Thirdly, we used a fibre cable deployed at the summit area of the volcano to test its ability to detect small volcanic events. In each of the three parts, a DAS system (iDASTM interrogator provided by Silixa) sent repeatedly coherent light pulses with a gauge length of 10 m and deduced the strain rate from interferometric measurements of the back-scattered light. We were able to measure every 2 metres the strain rate associated with several volcanic event types, earthquakes and many other signals from human activity. We validated the optical records with records from additional sensors such as seismic broadband stations, geophones and infrasound sensors. We present results from all experiments.