GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.2 GNGTS 2024 Mapping of volcanic deposits through the use of satellite techniques: the case of 2021 Mt. Etna eruptons M. Dozzo 1 , G. Ganci 1 , S. Scollo 1 , F. Lucchi 2 1 Isttuto Nazionale Geofsica e Vulcanologia, Sezione di Catania - Osservatorio Etneo, Catania, Italy 2 Dipartmento di Scienze Biologiche, Geologiche e Ambientali, Alma Mater Studiorum - Università di Bologna, Bologna, Italy During explosive eruptons tephra fallout represents one of the main volcanic hazards and can be extremely dangerous for air trafc, infrastructures, and human health. Here we present a new technique aimed at identfying the urban areas covered by tephra afer an explosive event based on the processing of PlanetScope satellite imagery. These recent multspectral data are acquired from a constellaton of over 180 microsatellites and exhibits a relatvely high spatal resoluton (~ 3 m pixel size) covering once a day each point in the Earth surface. Our technique is based on the introducton of a new index that we call ‘Tephra Fallout Index (TFI)’ computed from the mean refectance values of the near infrared (NIR) band analyzing pre- and post-eruptve data in paved areas adjacent to the summit craters of Etna and more distal paved areas, to have an overall view of the distributon of the tephra deposit. We use the Google Earth Engine computng platorm and defne a dynamic threshold for the TFI of diferent eruptve events to distnguish the areas afected by the tephra fallout. We demonstrate our technique by applying it to the eruptve events that occurred in 2021 at Mt. Etna (Italy), which mainly involved the eastern and south-eastern fanks of the volcano, sometmes two or three tmes within a day, making feld surveys difcult. Whenever possible, we compare our results with feld data and fnd an optmal match. The use of satellite imagery acquired from microsatellite constellatons, such as PlanetScope, providing an optmal compromise between spatal and temporal resoluton, may prove fundamental for identfying tephra deposits during eruptve episodes, such as those occurred in 2021 at Mount Etna volcano. In partcular, our method provides a near real tme result, making it ideal also for the mapping of other hazardous events worldwide. Corresponding author: maddalena.dozzo@ingv.it