Linking deformation to non-volcanic CO₂ degassing at Mefite d'Ansanto (Southern Apennines, Italy)

The Mefite d'Ansanto (MDA) degassing area, located in the Central Southern Apennines (Irpinia, Italy), is one of the largest non-volcanic CO₂ emission sites worldwide, with fluxes reaching ~2000 t/day. Geochemical signatures (R/Ra > 3) indicate a deep mantle–crustal origin for the fluids. MDA is located at the northwestern tip of to the Irpinia faults system which is responsible for major historical earthquakes in an active extensional domain where poor constrained Quaternary faults occur. Here, we present ~3 years of integrated geodetic and DEMs-based geomorphic observations aimed at constraining deformation and fluid migration processes at MDA. The dataset includes continuous GNSS measurements from 2022 to 2025 collected from a newly deployed local network, InSAR time series derived from 114 Sentinel-1 images acquired between 2020 and 2024, and multi-temporal UAV photogrammetry producing high-resolution digital surface models (DSMs). GNSS data reveal significant seasonal ground deformation, with horizontal displacements of up to ~40 mm and regional strain rates of ~2.2 mm/yr along NE–SW directions. InSAR results show localized vertical motions ranging between about −6 and + 4 mm/yr, with a linear trend overlapped to some fluctuations in the northeastern sector. UAV-derived DSMs, with resolutions up to 2.4 cm/pixel, enabled detailed mapping of more than 60 gas vents, fault scarps, and collapse features related to CO₂ degassing. For the first time, the integrated dataset reveals a clear separation between local and regional deformation signals, provides quantitative constraints on localized and seasonal deformation signals indicative of transient processes superimposed on regional extension and carbonate aquifer recharge. The observed deformation patterns highlight a strong sensitivity of shallow seasonal deformation to time-dependent forcing, primarily associated with hydrological loading within silicoclastic units. These results demonstrate the effectiveness of combined GNSS, InSAR, and geomorphic observations in distinguishing long-term tectonic deformation from short-term transient signals in fluid-rich extensional settings, providing new insights into strain localization mechanisms and surficial deformation processes at MDA.