Magnetic anomalies of the Phlegraean Caldera and surrounding marine sectors (Southern Tyrrhenian Sea)

Two high-resolution magnetic surveys, airborne and shipborne, were conducted over the offshore sector of Campi Flegrei, one of the most dangerous volcanic areas on Earth. The airborne data were integrated with historical onshore aeromagnetic surveys carried out by Agip S.p.A., resulting in a detailed map of magnetic anomalies across the entire caldera. The shipborne survey improved resolution over the Gulf of Bagnoli and its southern margin. The magnetic anomalies reveal complex linear and curvilinear patterns, mostly independent of surface structures. Spectral analysis indicates volcano-tectonic sources at depths up to 1.5 km, linked to magnetized mafic intrusions within faults and fractures, contrasting with the surrounding low- or non-magnetized volcanoclastic and sedimentary rocks. Within the caldera, the anomalies trend NW-SE and NE-SW, gradually rotating westward in the offshore. The new data improve our understanding of volcano-tectonic interactions and provide insights for risk assessment in the Phlegraean Fields.Key policy highlightsNew high-resolution airborne and shipborne magnetic anomaly maps of the Phlegraean Fields Caldera in Southern ItalyWidespread magmatic intrusions, lava fields, and volcanic edifices, aligned with fault systems, are identified through their magnetic signature.Linear to curved clusters of magnetic anomalies show the strong interplay between magmatic activity, volcanism and faults plus how the Phlegraean Fields fits within the regional tectonic.