Volatile Conduits Beneath Vulcano Island (Italy) Revealed by High‐Resolution Nodal Local Earthquake Tomography During Volcanic Unrest

Abstract

Understanding shallow magmatic and hydrothermal systems at active volcanoes is essential for interpreting unrest and forecasting eruptions. We present the first high‐resolution three‐dimensional Vp $Vp$ , Vs $Vs$ , and Vp/Vs $Vp/Vs$ models of Vulcano Island, Aeolian Islands, Italy, derived from a dense nodal seismic network. During 1 month of acquisition in 2021, coinciding with volcanic unrest, we detected and picked 1749 local earthquakes. Tomographic results reveal pronounced velocity anomalies, including high Vp/Vs ratios beneath Lipari and Vulcano, compatible with fluid‐rich zones, and low Vp/Vs anomalies compatible with gas‐ or vapor‐dominated reservoirs within the shallow magmatic–hydrothermal system. A deeper low Vp/Vs $Vp/Vs$ anomaly coincides with hypocentral depths of very‐long‐period seismic events, suggesting a genetic relationship between fluid accumulation, pressure buildup, and very‐long period seismicity. These results significantly improve travel‐time tomography resolution and provide new insights into the geometry, fluid distribution, and structural controls of Vulcano's upper plumbing system, with important implications for volcanic monitoring and planning strategies.