Audio-magnetotelluric and gravity surveys in Tectonically Active area: a case study of the L'Aquila-Scoppito Basin (central Italy)

This study aims to identify and characterize structures through geophysical investigations within a sector of the central Apennines (Central Italy). The research focuses on the L’Aquila-Scoppito Basin (ASB), which constitutes the western part of the larger L’Aquila intermontane basin. This area is notable for its high density of Quaternary faults and urban settlements of significant historical value. ASB is bounded by active normal faults responsible for significant historical and recent seismicity, with events of magnitude of up to M 6.5-7, including the Mw 6.29 earthquake that struck L’Aquila on April 6, 2009. The destructive effects of these events, including severe damage to the historic downtown and surrounding areas, are primarily attributed to the basin’s complex active faulting architecture.

To enhance the understanding of the subsurface structure, a combined audiomagnetotelluric (AMT) and gravity survey was carried out. Based on the inversion of data collected from 17 independent soundings in the study area, the AMT modelling provided a 2D electrical resistivity model of the subsurface. This model, integrated with surface geology and stratigraphic data from both deep and shallow boreholes, revealed the major structures of the ASB down to a depth of at least 1.5 km below ground level. Gravity observations were processed to obtain the Free-air, Bouguer and residual anomalies, along the same profile of the AMT, consisting of 14 points; the residual anomalies were modelled along the 2D profile, using the AMT results to constrain the subsurface bodies geometry. 

The integration of these datasets enabled the development of a detailed geological model of the subsurface and the identification of several faults. These findings contribute to the understanding of the fault architecture, that conditioned the evolution of the basin over the past 3-4 million years, and that controls the seismotectonic setting of this region.