3D Numerical Simulations of Non-Volcanic CO2 Degassing in Active Fault Zones Based on Geophysical Surveys

• Published in: Surveys in geophysics 2021-11, Vol.42 (6), p.1443-1478
• Main Authors: Di Maio, R., Salone, R., De Paola, C., Piegari, E., Vitale, S.
• Format: Article
• Language: English
• Subjects: Astronomy; Carbon dioxide; Carbon dioxide emissions; Carbonates; Degassing; Earth and Environmental Science; Earth Sciences; Electrical resistivity; Emissions; Fault lines; Fault zones; Faults; Flow estimation; Fluid dynamics; Fluid flow; Geochemistry; Geological data; Geology; Geophysical surveys; Geophysics; Geophysics/Geodesy; Hydrogeology; Integrated approach; Mathematical models; Modelling; Numerical simulations; Observations and Techniques; Polls & surveys; Seismic surveys; Simulation; Surveying; Three dimensional models; Tomography; Volcanic activity
• ISSN: 0169-3298; 1573-0956
• DOI: 10.1007/s10712-021-09666-0

An integrated approach that combines geophysical surveys and numerical simulations is proposed to study the processes that govern the fluid flow along active fault zones. It is based on the reconstruction of the architecture of the investigated fault system, as well as the identification of possible paths for fluid migration, according to the distribution of geophysical parameters retrieved by multi-methodological geophysical prospecting. The aim is to establish, thanks to constraints deriving from different types of data (e.g., geological, geochemical and/or hydrogeological data), an accurate 3D petrophysical model of the survey area to be used for simulating, by numerical modelling, the physical processes likely taking place in the imaged system and its temporal evolution. The effectiveness of the proposed approach is tested in an active fault zone in the Matese Mts (southern Italy), where recent, accurate geochemical measurements have registered very high anomalous values of non-volcanic natural emissions of CO 2 . In particular, a multi-methodological geophysical survey, consisting of electrical resistivity tomography, self-potential and passive seismic measurements, integrated with geological data, was chosen to define the 3D petrophysical model of the investigated system and to identify possible source geometries. Three different scenarios were assumed corresponding to three different CO 2 source models. The one that hypothesizes a source located along the fault plane at the depth of the carbonate basement was found to be the best candidate to represent the test site. Indeed, the performed numerical simulations provide CO 2 flow estimates comparable with the values observed in the investigated area. These findings are promising for gas hazards, as they suggest that numerical simulations of different CO 2 degassing scenarios could forecast possible critical variations in the amount of CO 2 emitted near the fault.