Gravity mapping of basement depth in seismogenic, fault-controlled basins: The case of Middle Aterno Valley (Central Italy)

Ground-shaking phenomena in intermontane basins emplaced in seismically active areas are strongly affected by sediment thickness. There, the development of human settlements, encouraged because of the flat topography in a mostly mountainous region, implies demographic growth and an increased seismic risk, as recent earthquakes in Central Italy confirmed. The knowledge of the thickness of the basin infills and of their density distribution is critical for the ground-motion amplification analysis. We apply the recently proposed ITerative RESCaling (ITRESC) method for 3D gravity modelling to the Middle Aterno Valley (Apennines, central Italy), a fault-controlled basin where a strong seismic activity recently occurred. Although the structural framework was previously investigated through 1D or 2D geophysical studies, here for the first time a full 3D model of the carbonate basement morphology is computed by the inversion of gravity data. Differently from usual gravity modelling approaches, the ITRESC technique 1) does not assume a density contrast function, which is instead determined through a data-driven process, and 2) integrates geological or geophysical constraints to define a global "gravity/depth-to-basement" resealing law, valid in all the investigated area. Our model integrates a number of depth constraints of different nature while at the same time honoring the gravity anomalies. The obtained gravity model of the basement depth shows several analogies with previous studies, although with significant, localized discrepancies. The results of this study are only partially consistent with a structural evolution of the Middle Aterno Valley through a polyphasic sequence, as previously hypothesized.