A Multidisciplinary approach for the determination of subsurface structure of Leonessa Plain (Central Appennines, Italy).

Abstract

n this study, detailed gravity survey and microtremor observations were made to map and model the thickness of Quaternary deposits (gravel, sand and clay) overlaying the Meso-Cenozoic pelagic basin deposits of the Leonessa plain. The study involved a test area of 50 km2 occupied by 300 gravity stations and by 30 sites of 3-component single-site observations. Stations were accurately located with differential GPS that provided centimetric accuracy in elevation. The microtremor data were analyzed by means of the horizontal-to-vertical spectral ratio (H/V). A realistic density of the unconsolidated Quaternary deposits (1.75-2,00 g/cm3) determined on core samples and a density of 2.60 g/cm3 for the basement limestone were used to constrain the 2D gravimetric models. The gravity and microtremor data were compared with a collection of existing well logs and geophysical data. The 2D models match quite well with the information determined from the previous works. The data obtained with these different methodological approaches allowed us to reconstruct the geometry of the depression and to evaluate the thickness of the Quaternary sedimentary infilling. Finally, on the basis of the obtained morphology, we were able to reproduce and to define the 3D model and the Quaternary evolution of the Leonessa plain.