What does gravimetry tell us about the “Salse of Nirano” mud volcanoes ?

Mud volcanoes are broadly distributed throughout the globe, both on land and below the seas (e.g. Martinelli and Panahi, 2006). In the last few decades mud volcanism has been widely investigated from the geological, geophysical, and geochemical points of view with important implications in energy resource exploration, seismicity, geohazard and greenhouse gas emissions (Mazzini and Etiope, 2017). They are formed by the episodic eruption of mud and rock fragments. The eruptions are mainly driven by of gravitative instability, due to the overall low density of clay strata on surrounding units and fluid overpressures. In 2014, the eruption of the Macalube di Aragona (Italy) mud volcano killed two children (Napoli et al., 2020). The eruption of the Piparo mud volcano (1997, island of Trinidad) damaged electrical and water infrastructures and killed animals and livestock (Blake et al., 2021). So that, the understanding of the mechanisms regulating mud volcanoes can be important also in terms of hazard evaluation. To date, a physical conceptual model of the Nirano Salse ascribes the eruptions to the presence of over-pressurized fluids that are expelled from a main deep reservoir. The latter is put into communication with the surface due to the episodically reactivation of pre-existing faults or pipes (Giambastiani et al., 2022, and ref. therein). The debate about this conceptual model is still open. To improve it, a new dataset of gravimetric data was acquired during 2022. The data are focused on an area located around the Salse di Nirano mud volcanoes. Our goal is to get an insight of the subsoil in the study area, having as a main target, the recognition of gas traps and faults. From the analysis of gravimetric data we found interesting information about the morphology and the physical conceptual model of the Salse di Nirano mud volcanoes.