Testing infrasound array technology for monitoring eruptive activity at Mt. Etna, Italy

Several studies have highlighted that infrasound is a powerful tool for volcano monitoring and holds promise to improve our understanding of volcano unrest and eruptive processes. As such, infrasound sensors are routinely deployed at active volcanoes, typically co­located with seismometer networks. Recent studies have demonstrated the value of deploying infrasound sensors in array configuration (clusters of few sensors at interstation of up a few tens of meters) at distances up to a few kilometers from active volcanic vents. Arrays provide a powerful tool for real­time detection and tracking the time evolution of eruptive activity, and can deliver real­ time estimates of eruption intensity. Here, we report the results of extensive testing of a 6­element infrasound array at Mt. Etna, Italy. The key objectives of the deployment were to assess the suitability of the chosen array location and configuration for future operational use at Mt. Etna, and evaluate its ability to provide a real­time assessment of eruption occurrence, location and intensity. The array was deployed between May 2021 and April 2022, during a period of intense activity and continuous eruption, characterized by frequent occurrence of paroxysmal activity. The array was deployed near to a permanent seismic station (EMNC) operated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) at the site Monte Conca, approximately 6 km from the South­East crater, the most active during the study period. The installation was optimized for maintenance­free deployment, throughout the snowy winter season, including a custom­made instrument housing and a dedicated solar power system. All data collected were processed with a slowness inversion algorithm; the results of these analyses demonstrated the ability of the array to detect the onset of eruptive activity and track its evolution, and to discriminate multiple active vents within the summit area at Mt. Etna. We conclude that the Monte Conca site is suitable for future deployment of a real­time, permanent, infrasound array, and the proposed configuration delivers satisfactory performances in terms of location uncertainty. This temporary deployment was supported by a collaboration between INGV Sezione di Pisa (PI) and Osservatorio Etneo (OE), and the University of Liverpool (UK).