DEMETRA - A Seismic Noise Survey at the Maccalube di Aragona Mud Volcanoes: Results and Perspectives

On 22–23 April 2025, a seismic noise survey was carried out at the Maccalube di Aragona mud volcano field (Sicily, southern Italy), with the aim of investigating the characteristics of the background seismic signal related to vent activity, and the shallow subsurface structure. The experiment, named DEMETRA (DEnse MaccalubE TRomino Acquisition), was conducted within the INGV–PROMUD multidisciplinary research project, aimed at identifying diagnostic indicators of mud volcano activity and potential precursors of paroxysmal events. Ambient seismic noise was acquired at 21 sites using three-component, 24-bit digital tromograph deployed with a high spatial density across vent zones and surrounding areas. The data analyses include spectral characterization, horizontal-to-vertical spectral ratio (HVSR) computation, and estimate of the polarization pattern of the recorded signals. The HVSR results do not reveal distinct amplification peaks but instead show site-dependent deamplification features. Polarization analysis highlights coherent directional patterns within the vent areas. Furthermore, transient signals embedded in the background noise were detected at some sites; their spectral content and polarization properties suggest a possible association with degassing processes, mud emissions, or surface bubbling phenomena. Owing to its dense spatial coverage, the DEMETRA experiment provides a valuable dataset for improving the understanding of subsurface properties and dynamic processes in active mud volcano systems.