Investigating fault reactivation during multiple tectonic inversions through mechanical and numerical modeling: An application to the Central-Northern Apennines of Italy

Within inversion tectonic contexts, the reactivation of pre-existing discontinuities depends upon many structural, stratigraphic and mechanical factors. Among these, a fundamental aspect is represented by the orientation and attitude of pre-existing discontinuities with respect to the new stress field. The aim of this work is to evaluate the stress regimes and the mechanical conditions that controlled the reactivation of segmented pre-thrusting normal faults in the Central-Northern Apennines of Italy. These faults were involved both in positive and negative inversion tectonic events during Tertiary-Quaternary times. Mechanical (slip tendency analysis) and numerical (using COULOMB 3.3 software) models allowed us to reconstruct a 3D stress field for both inversion events and to evaluate the effect of many parameters (orientation of faults, fault dip-angle and mechanical parameters) on fault reactivation. Our results highlighted that the orientation of pre-existing faults with respect to the stress axes represents the main factor controlling inversion tectonic phenomena, where other mechanical and geometric variables exert a subordinate role. The models well reproduce the Neogene-Quaternary deformation history reconstructed from detailed geological and structural analyses for the Central-Northern Apennines of Italy and could be applied to other regions that have experienced inversion tectonic processes.