Preliminary results from the INGV-PROMUD Project: seismic and hydromorphological monitoring of Maccalube di Aragona Mud Volcano (Sicily, Italy).

The INGV-PROMUD is a 3-years (2023-2025) multidisciplinary project (https://progetti.ingv.it/it/promud), aimed to investigate the indicators of the activity of MVs, with the ultimate goal of individuating possible precursors of paroxysmal events. Its two main target areas, both in Italy, are the ‘Salse di Nirano’ (Northern Apennines) and the ‘Maccalube di Aragona’ (Sicily).

Among the multidisciplinary research activities carried out in the scopes of the project, particular attention is focused on the analysis of the background seismic noise wavefield, and its role in the identification and monitoring of degassing sources and conduits, and of the hydrological regime, and its influence on MVs activity.

Seismic data have been recorded at Aragona, since July 2024, by six seismometers, four of which are part of a seismic array located close to the vents, with the aim of investigating the characteristics of the recorded background seismic noise, e.g., spectral properties, H/V spectral ratios, energy (RMS) and polarization temporal pattern. Preliminary results of data recorded from July to September 2024 show that the main frequency content of the wavefield is below 5 Hz. H/V spectral ratios are almost flat, indicating the absence of amplification effects, at least in the investigated sites. The temporal pattern of the RMS amplitude is affected by some fluctuations, which need to be further investigated to look for evidences of a possible periodic behaviour. The polarization parameters (azimuth, incidence angle and rectilinearity) appear to be stable over the whole analysed time interval. At the array site, in the 0.2-1 Hz frequency band, the noise wavefield is polarized along the NS direction, while polarization azimuths 1-5 Hz band are more disperse.

Seismic monitoring has been coupled to near real time acquisition of meteorological data and temperature, volumetric water content and electric conductivity of soil, integrated by monthly surveys of number and position of active mud emitting vents, and apparent soil moisture content distribution.

First analyses of the acquired data indicate that the hydrological cycle exerts a strong control on both number and distribution of vents, and on the rheological properties of the emitted fluids, playing a potential role in determining pressure accumulation, prodromic to paroxysmal events.