Geo-Structural Evidence for Active Oblique Extension in South-Central Italy

Possible Location of the Next Major Earthquakes in the Northern Apennines: Present Key Role of the Romagna-Marche-Umbria Wedge

“…In the Central Apennines, the transtensional decoupling between the eastern and western sectors of the ELA wedge is mainly accommodated by the L'Aquila and Fucino fault systems [32] [43]. In the Northern Apennines, extensional tectonics mainly occurs along the internal boundary of the RMU wedge, corresponding to the Alta Valtiberina, Valle Umbra, Leonessa and Rieti troughs and to a youngest almost parallel fault system that develops from the Laga mountains to the Gubbio zone, through the Norcia, Colfiorito and Gualdo Tadino zones [30] [32] [42] [44] [45].…”

Belt-Parallel Shortening in the Northern Apennines and Seismotectonic Implications

“…The oblique divergence between the mobile Apennine wedges and the inner, less mobile belt has been accommodated by extensional and sinistral transtensional deformation, mainly concentrated in the axial zones, where a series of continental intramontane basins has developed in the Quaternary [23]. This context has also involved compressional deformation at the outer front of the extruding wedges, where they over thrust the Adriatic domain [24].…”

“…When a strong shock occurs at the inner extensional decoupling boundary of the MS wedge (Irpinia-Benevento-Matese fault system [8] [27]- [29]) that block accelerates, increasing its belt-parallel push on the eastern part of the LA platform. This indentation induces shear stress at the sinistral transtensional faults (L'Aquila and Fucino [4] [8] [23] [30] [31]), that are located at the boundary between the stressed and non-stressed sectors of LA.…”

“…Correspondingly, the sector of the RMU wedge in the Northern Apennines that is stressed by such push is narrow as well. This interpretation may explain why the major belt-parallel fault system Norcia-Colfiorito-Gualdo TadinoGubbio (No-Cf-GT-Gu in Figure 2), roughly running along the northward prosecution of the L'Aquila fault system has developed within the RMU wedge since the late Quaternary [23] [30] [32]. Such major fracture, and its possible northward prosecution in the Upper Tiber and Romagna-Forli fault systems, might represent the inner extensional/transtensional border of a wedge that will be hereafter recalled as Outer Romagna-Marche-Umbria (ORMU in Figure 2).…”

Quaternary evolution of the Lucania Apennine thrust front area (Southern Italy), and its relations with the kinematics of the Adria Plate boundaries

“…Southwards, offshore the Taranto Gulf, the thrusting apparently ceased later at 0.2-0.3 Ma (Pieri et al, 1997). After the cessation of thrusting, a new tectonic regime affected the Southern Apennines wedge manifesting a major geodynamic change characterised by generalised uplift and extensional and strike-slip faults that has been dismembering the thrust belt (Pantosti and Valensise, 1990;Catalano et al, 1993;Cinque et al, 1993;Hippolyte et al, 1994a;Bordoni and Valensise, 1998;Cello et al, 2003;Piccardi et al, 2006). The strike-slip faulting probably resulted from the reactivation of inherited brittle discontinuities in the Apulian Platform beneath the fold-and-thrust belt (Bonini and Sani, 2000a, and references therein).…”