The September 27, 2012, ML 4.1, Benevento earthquake: A case of strike-slip faulting in Southern Apennines (Italy)

The 2013–2018 Matese and Beneventano Seismic Sequences (Central–Southern Apennines): New Constraints on the Hypocentral Depth Determination

“…These observations confirm the progressive eastward migration of the active belt that is due to nucleation of younger splay faults and to the deactivation of the break-away zone and the western faults of the system [24]. [69,86]. In fact, the Apenninic area where the Apennine units overthrust the Apulian crust is characterized by an articulated rheological layering, with two brittle layers located at different depths: a brittle upper crust (9 km to 12 km thick), with the Apennine extensional seismicity, overlaying a ductile middle and lower crust, and a thick brittle, possibly seismogenic crust (21-23 km thick, the Apulia foreland including the sedimentary cover and part of the middle crust) which overlies a ductile lower crust [69].…”

“…Similar seismicity, with right lateral strike-slip kinematics and deep hypocenters, was observed with the Monteleone di Puglia (ML 4.9) earthquake of the 6 May 1971 [85] (Gasparini et al, 1985), during the two sequences that struck the region around Potenza (Basilicata) between 1990 (ML 5.7) and 1991 (ML 5.2; [68]) and with the 27 September 2012, ML 4.1 Benevento earthquake [86]. Moreover, pure right-lateral slip between 10 km and 24 km depth over a nearly vertical east-west fault occurred in the 2002 San Giuliano di Puglia (eastern Molise) sequence [42] [69,86].…”

“…Similar seismicity, with right lateral strike-slip kinematics and deep hypocenters, was observed with the Monteleone di Puglia (ML 4.9) earthquake of the 6 May 1971 [85] (Gasparini et al, 1985), during the two sequences that struck the region around Potenza (Basilicata) between 1990 (ML 5.7) and 1991 (ML 5.2; [68]) and with the 27 September 2012, ML 4.1 Benevento earthquake [86]. Moreover, pure right-lateral slip between 10 km and 24 km depth over a nearly vertical east-west fault occurred in the 2002 San Giuliano di Puglia (eastern Molise) sequence [42] [69,86]. In fact, the Apenninic area where the Apennine units overthrust the Apulian crust is characterized by an articulated rheological layering, with two brittle layers located at different depths: a brittle upper crust (9 km to 12 km thick), with the Apennine extensional seismicity, overlaying a ductile middle and lower crust, and a thick brittle, possibly seismogenic crust (21-23 km thick, the Apulia foreland including the sedimentary cover and part of the middle crust) which overlies a ductile lower crust [69].…”

“…In fact, the Apenninic area where the Apennine units overthrust the Apulian crust is characterized by an articulated rheological layering, with two brittle layers located at different depths: a brittle upper crust (9 km to 12 km thick), with the Apennine extensional seismicity, overlaying a ductile middle and lower crust, and a thick brittle, possibly seismogenic crust (21-23 km thick, the Apulia foreland including the sedimentary cover and part of the middle crust) which overlies a ductile lower crust [69]. We have in this area the coexistence of two different stress regimes, vertically overlapping, a shallow extensional one (<15 km) and a deep transcurrent one (20-25 km) with a common SW-NE direction of the σ 3 principal stress [69,86]. The seismotectonic environment of these sequences is of regional importance.…”

Detecting long-lasting transients of earthquake activity on a fault system by monitoring apparent stress, ground motion and clustering

“…Several previous studies 40–42 showed that the northern and southern Irpinia sectors are characterized by a complex tectonic, as resulting from the overlap of a strike-slip regime (i.e., related to the Benevento and Potenza faults to the north and to the south, respectively) with the extensional regime dominating the central sector of the Irpinia fault. Since such tectonic complexities would require a specific interpretation of the results for each sector, we restrict our interest to the more densely instrumented central sector of the Irpinia fault for studying the time evolution of τ a .…”