Geochemistry within the Near Fault Observatory: the Alto Tiberina case study (Italy)
Authors: Caracausi Antonio , Buttitta Dario , Camarda Marco , Chiaraluce Lauro , De Gregorio Sofia , Favara Rocco , Pisciotta Antonio Fabio 
Published: March 2024

Understanding multi-scale chemical-physical processes, which control rock deformation, faulting, and seismicity, requires the examination of processes at the boundaries between different research fields, and the availability of multidisciplinary long-term series of data. The Alto Tiberina Near Fault Observatory (TABOO-NFO) located in the upper Tiber Valley within the inner sector of the northern Apennines (Italy) has been created to fulfill this aim. TABOO-NFO is a state-of-the-art monitoring infrastructure composed of an array of seismic, geodetic, strain, and geochemical sensors. The infrastructure, continuously monitors at a high rate and resolution a relatively small and actively deforming area (about 120 km &#215; 120 km), and allows to study various parameters connected to the deformation processes, active along a crustal fault system dominated by the Alto Tiberina fault (ATF). It is a 60 km long normal fault dipping at a low angle (<15&#176;&#8211;20&#176;). The region is characterized by the presence of over-pressurised fluids trapped at certain depths in the crust and superficial manifestations associated with the emission of large quantities of fluids (mainly CO2).The ATF strongly influences the redistribution of CO2 -rich emissions at regional scale and represents a key pathway for gas transfers from crustal natural reservoirs of fluids to the surface.Indeed, the gases tend to escape from the overpressurised reservoirs via low-permeability zones mainly placed along tectonic discontinuities present in the upper crust. In this framework, the area of the ATF represents a natural laboratory to investigate the relationship between soil CO2 fluxvariations and tectonic crustal stress.To this aim within TABOO-NFO we deployed a network of four stations to continuously monitor the soil CO2 flux in the surrounding of CO2 -rich gas emissions and we performed periodic monitoring of the chemical and isotopic composition of gases emitted in main vents of seepage sites. The contemporary record of high-frequency geophysical and geochemical parameters, along with the periodic acquisition of more detailed geochemical data in the seismogenic area, is the key to building conceptual models that can describe the relationship between fluid emissions, seismicity patterns and faulting (Caracausi et al., 2023).Over the course of the TABOO-NFO activities, ongoing monitoring of high-frequency geophysical and geochemical parameters, will provide the basis for building robust conceptual models of the main processes along the fault zone that influence the chemistry of the fluids themselves. Thesemodels are essential for a comprehensive understanding of the complex dynamics of fluid emissions, seismicity patterns and faulting processes.In summary, the TABOO-NFO stands as a cutting-edge research initiative that combines advanced monitoring technologies with a multidisciplinary approach. The project aims to enhance understanding of the fundamental processes driving rock deformation, faulting, and seismic activityin the region.
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References
Caracausi A., Camarda M., Chiaraluce L., De Gregorio S., Favara R., Pisciotta F.A., (2023), A novel infrastructure for the continuous monitoring of soil CO2 emissions: A case study at the Alto Tiberina Near Fault Observatory in Italy. Frontiers in Earth Science, DOI 10.3389/feart.2023.1172643