Geological hazard assessment of the coastal area of Rome (Central Italy) from multi-source data integration

Abstract

This work presents the first 3D geological model of the Rome coastal area that integrates available subsurface geological, stratigraphic and geophysical data with surface geochemical data obtained both from the literature and new surveys. The model provides new insights into the stratigraphic and tectonic setting of the area and the geological factors controlling both natural and human-induced gas emissions. This sector of the Italian Tyrrhenian margin has been historically affected by natural emissions of deep CO2 and thermogenic CH4, stored in permeable layers but with local migration to the surface along buried normal faults. In addition to natural processes, human activities can also cause leakage and serious health risks, such as the abrupt gas release in August 2013, that was triggered by borehole drillings near the Rome international airport. The presented 3D reconstruction unveils the link between faults, stratigraphy, lithology and the distribution of the soil gas anomalies. It provides information about the depth of the reservoir that can potentially trap endogenous gases, and the location and geometry of the main faults along which the gas migrates towards the surface. Furthermore, reconstruction of the distribution and thickness of important clay layers better constrains the low permeable areas that prevent gas escape. The 3D model, coupled with the geochemical information, can serve as a useful tool for the local administration to perform land-use planning and manage the local geological and degassing hazards that affect this highly urbanized area near Rome. Furthermore, we estimate that the large amount of CO2 broadly released in the area also provides a contribution to the budget of natural greenhouse gases in the atmosphere.