A 34-Year Record of Seismic Activity at Vulcano Island, Italy

Following the abrupt geochemical and geophysical variations that occurred on the island of Vulcano in September 2021, the search for previous multidisciplinary data on decades-long time spans became necessary to contextualize the newly recorded anomalous variations, which represented a serious threat for the local population. Our analyses of ‘vintage’ reports, old documents and analog seismograms broaden our understanding of crustal seismic activity. The results unravel the predominant role of the Vulcano’s hydrothermal system with respect to tectonic processes in the generation of seismicity in the analyzed sector. Earthquakes were generally located offshore and achieved a maximum M4.6. A 3D strain release map and DBSCAN application highlight seismogenic volumes to NW, SW, E offshore the island and trending NNW-SSE inshore, in agreement with structural pattern. Two major volcano unrests in 1985 and 1988 had seismicity mostly confined to the island. In comparison, the longer duration and typology of seismic signals recorded between 2021 and 2022 make this latest episode peculiar in the context of Vulcano’s past seismic activity.