Architecture of active extensional faults in carbonates: Campo Felice and Monte D'Ocre faults, Italian Apennines

To understand better the development of deformation in carbonate-hosted normal faults, we compared the structural architecture of the Campo Felice and Monte D'Ocre active faults (Italian central Apennines). The two geometrically linked structures displace the same carbonate sequences, but with different Quaternary slip rates and geological throws. Moreover, several geomorphological features typical of deep-seated landslides were identified across the Mt. D'Ocre range. The Campo Felice fault segment and the Cama fault segment (Monte D'Ocre range) consist of 0.4–15 m thick and almost absent fault cores and of >400 m and <40 m thick damage zones, respectively. The associated slip zones have different fabrics (i.e., cataclasite vs. crush fault breccia for Campo Felice and Cama Fault, respectively). The different fault zone architecture and associated landscapes would suggest different behaviors of the two faults although similar deformation mechanisms (i.e., cataclasis and pressure-solution) are active in both the two scarps. The Mt. D'Ocre faults would not be segments of the Ovindoli-L'Aquila Fault System and currently accommodate the lateral spreading of the Mt. D'Ocre ridge. Therefore, the seismic hazard associated with the fault system might be reduced. This work shows how macro-to micro-structural analyses provide further information to improve the structural characterization of seismogenic sources.