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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. Plain Language Summary: Mud volcanoes are broadly distributed throughout the globe, both on‐and off‐shore. 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 on surrounding soil types and fluid overpressures. To date, a physical conceptual model of the area of Nirano Salse (Northern Italy), ascribes the mud 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 episodical reactivation of pre‐existing faults or pipes. The debate about this conceptual model is still open. To improve it, a new data set of gravimetric data was acquired during 2022. Our results suggest that the morphology of the study area is due to the presence of an almost vertical fault, which acts as a preferential route for the ascent of deep fluids. Key Points: A microgravimetric survey coupled with laboratory density measurements allows to image the shallow to medium subsurface below mud volcanoesGravimetric data allow to distinguish between morphologies due to caldera collapse and the surface expression of slip along a faultFor the first time the attenuation volume caused by mud intrusion is imaged by gravimetry along a fault [ABSTRACT FROM AUTHOR]

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Abstract: During the Miocene, hydrocarbon seep-carbonates located atop intrabasinal highs and associated with sediment instability, formed commonly at the deformation front of the Northern Apennine collisional orogen. The parallelism between the structural trend and the distribution of seep-carbonates suggests a close relationship between tectonics and gas/fluid emission. The “Montepetra intrabasinal high” was formed during the closure stage of the foredeep, being related to the synsedimentary growth of an anticline. Field geometry suggests that detachment folding was the leading mechanism of anticline growth and synsedimentary instability along the anticline flanks. Ten different bodies of seep-carbonates occur in the Tortonian–early Messinian sediments: nine in the hinge zone and one in the southern backlimb of the anticline. Foraminiferal study, geochemistry, facies investigation and the three-dimensional geometry of carbonate bodies with respect to the encasing terrigenous sediments indicate a protracted (late Tortonian–early Messinian) activity of fluid migration with re-mobilization and ascent of sediments from the core of the anticline, stabilization of chemosynthesis-related communities, and in-situ brecciation. Seepage atop the intrabasinal high was fed by different circuits: one related to the compaction-dewatering of shallow (Tortonian–early Messinian) sediments, and a deeper one related to the deformation of the anticline core and to the activity of detachment surfaces and of faults propagating through the sedimentary cover. [ABSTRACT FROM AUTHOR]