Gravity Data Allow to Image the Shallow‐Medium Subsurface Below Mud Volcanoes

Abstract

The debate about the conceptual model of mud volcanoes functioning is still alive in the literature. A large part of the literature focuses on the characterization of the deep reservoir where expelled fluids are expected to originate. Another part of literature is focused on the study of the shallow system of mud volcanoes, which could influence the short‐term variations in mud volcanoes activity. We present and analyze a new data set of micro‐gravimetric data to study the area of the Nirano Salse, Italy. Unlike what is commonly assumed for the study area, our results suggest that the geomorphology of the Nirano Salse is not related to a caldera collapse above a shallow mud chamber, but to the surface expression of slip distribution of a fault termination along which the fluids ascended to the surface. We believe that gravimetric data can significantly improve the study of hydrocarbon seeps and mud volcanism.

Structural Control on Carbon Emissions at the Nirano Mud Volcanoes – Italy

“…1), and the gravimetry (Fig. 3S) (Nespoli et al, 2023), whereas the NNE-SSW trend could be related to transfer or strike-slip faults at high angle to the Northern Apennines fold axis (Fig. 7) as proposed by Vannoli et al (2021) (see also top inset in Fig.…”

“…Structural data from our geologic survey, surface gas emissions, and available geologic maps (Gasperi et al, 2005) as well as recently published dipole-dipole electric tomography (see Figs. 8, 9, and 10 in Romano et al, 2023) and gravimetry data by Nespoli et al (2023) are presented in the map of Fig. 7 and in Fig.…”

“…Recent gravimetric data from Nespoli et al (2023) show the existence of a NW-SE oriented 250 m wide low-density zone that extends down to a depth of 800 m in the northern portion of the Nirano Salse (Figs. 8 and 3S in this work and Fig.…”

“…8-10 in Romano et al, 2023). Based on the characteristics of the gravimetric and resistivity anomalies, Nespoli et al (2023) interpret the low-density zone as the damage zone of a sub-vertical NW-SE oriented normal fault invaded by gas and mud (Figs. 8c and 3S in this work and Fig.…”

“…In this paper, we investigate the relationships between gas emissions and local structures in the Nirano Salse (Italy), which is a well-studied site where geochemical, geophysical, and structural data are available (Bonini, 2007(Bonini, , 2008(Bonini, , 2009Giambastiani et al, 2022;Heller et al, 2011Heller et al, , 2012Lupi et al, 2016;Martinelli and Rabbi, 1998;Nespoli et al, 2023;Romano et al, 2023;Sciarra et al, 2019). We examine both natural gas macro-, mini-and micro-seepages for relating their venue to structural elements such as faults and fractures.…”