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The Irpinia Fault (i.e., Mount Marzano Fault System: MMFS) was responsible for the devastating 1980 earthquake (Mw 6.9) that caused the longest surface faulting ever observed in Italy (> 30 km). Early paleoseismological studies have revealed a ∼ 2 kyr recurrence time for 1980-like characteristic earthquakes on this fault system during the Holocene. However, this appears to clash with both the catastrophic historical seismicity and high GPS-derived strain rate of the area. To explain this apparent discrepancy, we investigated the MMFS through a multidisciplinary approach. First, on the basis of recent archives and archaeological research, we reassessed the historical seismicity of the area, analysing the highest intensity distribution of the major earthquakes of the upper Ofanto Valley, with respect to the MMFS hanging wall. Then, we carried out a step-by-step survey along the entire 43-km-long fault system, through both high precision topographic levelling along the compound fault scarp and geostructural analyses. Finally, we excavated trenches and pits across different fault segments, to explore the recent paleoseismological history of the structure. Based on the combined results that we have obtained, we propose a different point of view concerning the seismogenic behaviour of the MMFS from the Holocene to the Present. At the end, fault parameters have been compared with those of all the Apennines active faults, and cross-checked with the newest GPS results in peninsular Italy, providing some relevant observation of the relationships between seismogenesis and geodetic deformation. [ABSTRACT FROM AUTHOR]

An integrated investigation including geological, geomorphological, geophysical and structural survey, tephra analyses, 14 C and 40 Ar/ 39 Ar dating, as well as paleoseismic trenching along the N-Matese fault system is presented. The study allowed the characterization of the tectonic mobility of this structure as well as the associated Bojano basin sedimentary-tectonic evolution since the early Middle Pleistocene, providing also new clues concerning the fault historical activity and the associated Mw > 6.5 earthquakes. We have found lines of evidence for > 1 mm/yr slip rate along the presently buried Bojano fault during the mid Middle Pleistocene, and similar rates for the main fault segments paralleling the Matese flanks. The buried Bojano fault significantly slowed down during the last 300 kyr, ceasing its activity before the Holocene. In turn, the segments outcropping along the Matese flanks reactivated at the onset of Late Pleistocene, after a long period of quiescence (480–110 ka), with robust slip rates that would seem even accelerating in post LGM times. Paleoseismic data suggest the occurrence of four Mw > 6.6 earthquakes in the past 3 ka, three of which match the little known 280 BC event, and the devastating 1456 and 1805 earthquakes. [ABSTRACT FROM AUTHOR]

Abstract: Morphological, stratigraphical and structural investigations integrated with palaeomagnetic and tephrostratigraphic studies and 40Ar/39Ar measurements allowed us to define the Quaternary tectonic–sedimentary evolution of the epicentral area of the L''Aquila 2009 earthquake (Mw 6.3). This area roughly matches the Paganica–San Demetrio–Castelnuovo (PSC) intermountain basin filled by a fluvio-lacustrine succession that is variously deformed by normal faults. At its early stage (Early Pleistocene; ca 2 Ma), the basin hosted a lake that was characterised by whitish carbonate silt and mud deposition. Towards the end of the Early Pleistocene, this was partly filled by a south-eastward prograding deltaic system. The south-easternmost portion of the deltaic system was successively abandoned and eroded, while sedimentation of a braided river system developed in a smaller area westwards. Before 780 ka, this fluvio-lacustrine system (the Lower PSC syntheme) ended, and the area underwent erosional and pedogenic processes. These processes continued up to >460 ka, with the onset of fluvial gravel and volcanic-rich silty sand deposition over a narrow area of the south-western PSC basin (an earlier unit of the Upper PSC syntheme, early Middle Pleistocene). Around 460 ka, when most of this area was again subjected to denudational processes, the sedimentation migrated into the previously exposed north-western area of the PSC basin, where fluvial/alluvial sediments were deposited, between ca 460 ka and ca 350 ka (a later unit of the Upper PSC syntheme). Between ca 350 ka and the present, the sedimentation continued uninterrupted in a slight westwards restricted area of the PSC basin (Upper–Late PSC syntheme). The significant contraction of the basin, the shifting of its depocentre, the variation in its geometry and in the spatial distributions and thicknesses of the units constituting the Lower, Upper and Late PSC synthemes, provide evidence for strong tectonic control. This resulted in progressive reduction of the activity of the south-easternmost tectonic structures and parallel migration of the fault activity on the westernmost structures. In this perspective, the fault system responsible for the L''Aquila 2009 earthquake can be seen as the most recent expression of a long-lasting westwards polarised process of tectonic activity transfer. [Copyright &y& Elsevier]