Figure 4

Sketch view of the main results of this study, highlighting the two anomalies of low Vp and low Vp/Vs we found beneath central-northern Vulcano and the western offshore of Lipari. In map we reported the tomographic results at 2 km depth in terms of Vp/Vs together with the Vp anomalies corresponding to a value of − 6% (purple lines). Isobaths of seafloor depth in correspondence with the main anomalies and sectors of documented hydrothermal activity²⁴ are also shown (see legend). Along the vertical section cutting the two anomalies (see the profile in map) we analogously reported the Vp/Vs distribution and the contour lines of Vp-variation equal to − 6%. White dots represent the high gas content areas.