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We present a marine paleoseismology analysis of a dense network of very high resolution seismic profiles along the Gondola Fault Zone (GFZ), a right-lateral, E-W–striking, active fault system in the Adriatic foreland. This case-study aims to show how time and space variations in the activity of a dominantly right-lateral fault system can be assessed based on the vertical component of slip alone. The GFZ has been investigated for a length of 50 km. It includes two parallel subvertical fault sets and two main anticlines. The distribution of the late Middle Pleistocene to Holocene vertical component of displacement along-fault is bell-shaped, suggesting that in the long-term the fault zone acts as a single, kinematically coherent structure. Slip rates on individual fault segments, however, suggest that they may rupture independently. Vertical slip rates calculated for late Middle Pleistocene-Holocene intervals fall in a narrow range and are consistently small (0-0.18 mm/a).

Recent seismicity in and around the Gargano Promontory, an uplifted portion of the Southern Adriatic Foreland domain, indicates active E–W strike-slip faulting in a region that has also been struck by large historical earthquakes, particularly along the Mattinata Fault. Seismic profiles published in the past two decades show that the pattern of tectonic deformation along the E–W-trending segment of the Gondola Fault Zone, the offshore counterpart of the Mattinata Fault, is strikingly similar to that observed onshore during the Eocene–Pliocene interval. Based on the lack of instrumental seismicity in the south Adriatic offshore, however, and on standard seismic reflection data showing an undisturbed Quaternary succession above the Gondola Fault Zone, this fault zone has been interpreted as essentially inactive since the Pliocene. Nevertheless, many investigators emphasised the genetic relationships and physical continuity between the Mattinata Fault, a positively active tectonic feature, and the Gondola Fault Zone. The seismotectonic potential of the system formed by these two faults has never been investigated in detail. Recent investigations of Quaternary sedimentary successions on the Adriatic shelf, by means of very high-resolution seismic–stratigraphic data, have led to the identification of fold growth and fault propagation in Middle–Upper Pleistocene and Holocene units. The inferred pattern of gentle folding and shallow faulting indicates that sediments deposited during the past ca. 450 ka were recurrently deformed along the E–W branch of the Gondola Fault Zone. We performed a detailed reconstruction and kinematic interpretation of the most recent deformation observed along the Gondola Fault Zone and interpret it in the broader context of the seismotectonic setting of the Southern Apennines-foreland region. We hypothesise that the entire 180 km-long Molise–Gondola Shear Zone is presently active and speculate that also its offshore portion, the Gondola Fault Zone, has a seismogenic behaviour.

Fold-thrust belts are commonly interpreted as "thin-skinned" structures, developed above a detachment, with the underlying basement remaining undeformed. However, in many areas, particularly where compressional tectonism was preceded by rifting, models of basement fault reactivation may be more appropriate. The contrasts between thin-skinned and deep-rooting, inversion-dominated deformation in building fold-thrust complexes are investigated using a case history from the Italian Apennines. Three sectors were chosen to represent the marked lateral variations in structural style evident in the thrust belt. The outer portion of the Marche (in the north) is contrasted with a section through the Lucanian Apennines in the south and with the Molise district of the Central Apennines. The Marche structures are readily explained in terms of inversion, a model that is consistent with new deep seismic data onshore and conventional seismic from the nearby Adriatic Sea. The displacements implicit for the inversion model are a factor of five less than for existing thin-skinned interpretations. However, these styles are not applicable throughout the Apennines. Well data in the Southern Apennines of Lucania demonstrate large-scale thin-skinned thrusting, with 57 km of horizontal displacement since earliest Pliocene time. This includes 14 km of shortening that ramps up through the buried Apulian Platform carbonates. These deeper structures may be restored using ramp-dominated thrust geometries. The Molise sector shows broadly the same structural style as for Lucania: allochthonous shallow-water carbonates and pelagic basin units overlie the carbonates of the Apulian Platform, with the major difference being that here, the pelagic basin units are detached at the level of the Oligocene-lower Miocene Argille Varicolori. In this setting, the Apulian carbonates may be restored using only 5 km of displacement. The overlying allochthon probably has accommodated about 45 km of displacement since the earliest Pliocene. Therefore, the Apennines show differing structural styles with differing displacements along their length. Thick-skinned thrusting models may be applied to the Marche and to structures in the buried Apulian units.

This paper focuses on the boundary area between the Central and Southern Apennines thrust belt of the Italian peninsula, which separates two different patterns of distribution of active faults and strong earthquakes along the Apennines chain. In order to reduce the remarkable lack of data on this area, part of this boundary has been investigated. The study area corresponds to the surroundings of the town of Isernia, an important centre of the Molise region, and contains the Carpino and Le Piane (CLP) intermountain Basins of Quaternary age. The research was based on unpublished data, consisting of 65 well logs drilled in the CLP Basins, integrated with detailed field surveys (scale 1:10,000), mesoscale structural analysis and aerial photograph interpretation. This study allowed to define the geometry and kinematics of the CLP Basins. They result to be asymmetric halfgrabens partially filled with fluvio-lacustrine deposits, where the sedimentation is controlled by the activity of a set of normal faults striking N30jW and NE dipping. This set of faults, which developed mainly during the Late Pleistocene–Holocene, is about 10 km long and is located close to the northwestern end of the Boiano Basin extensional Fault System. The average slip rate calculated for part of the Holocene for one of the recognised faults ranges from 0.75 to 1.00 mm/year. The identification of the active CLP Basins Fault System partially fills the gap of data at the boundary between the Central and Southern Apennines. From a more general point of view, we hypothesise that this boundary might be regarded as a ‘‘persistent segment boundary’’, forming a long-term barrier to the propagation of rupture of active fault systems. Under this perspective, a redefinition of the seismic zonation of Italy for the study area is suggested. D 2002 Elsevier Science B.V. All rights reserved.

The NEAM Tsunami Hazard Model 2018 (NEAMTHM18) is a probabilistic hazard model for tsunamis generated by earthquakes. It covers the coastlines of the North-eastern Atlantic, the Mediterranean, and connected seas (NEAM). NEAMTHM18 was designed as a three-phase project. The first two phases were dedicated to the model development and hazard calculations, following a formalized decision-making process based on a multiple-expert protocol. The third phase was dedicated to documentation and dissemination. The hazard assessment workflow was structured in Steps and Levels. There are four Steps: Step-1) probabilistic earthquake model; Step-2) tsunami generation and modeling in deep water; Step-3) shoaling and inundation; Step-4) hazard aggregation and uncertainty quantification. Each Step includes a different number of Levels. Level-0 always describes the input data; the other Levels describe the intermediate results needed to proceed from one Step to another. Alternative datasets and models were considered in the implementation. The epistemic hazard uncertainty was quantified through an ensemble modeling technique accounting for alternative models’ weights and yielding a distribution of hazard curves represented by the mean and various percentiles. Hazard curves were calculated at 2,343 Points of Interest (POI) distributed at an average spacing of ∼20 km. Precalculated probability maps for five maximum inundation heights (MIH) and hazard intensity maps for five average return periods (ARP) were produced from hazard curves. In the entire NEAM Region, MIHs of several meters are rare but not impossible. Considering a 2% probability of exceedance in 50 years (ARP≈2,475 years), the POIs with MIH >5 m are fewer than 1% and are all in the Mediterranean on Libya, Egypt, Cyprus, and Greece coasts. In the North-East Atlantic, POIs with MIH >3 m are on the coasts of Mauritania and Gulf of Cadiz. Overall, 30% of the POIs have MIH >1 m. NEAMTHM18 results and documentation are available through the TSUMAPS-NEAM project website (http://www.tsumaps-neam.eu/), featuring an interactive web mapper. Although the NEAMTHM18 cannot substitute in-depth analyses at local scales, it represents the first action to start local and more detailed hazard and risk assessments and contributes to designing evacuation maps for tsunami early warning.

Combined structural and geophysical investigations were carried out in the Matese Massif at the boundary between the Central and the Southern Apennines. The aim of this research was to define the structural geometry and the kinematics of Neogene deformation in order to validate the applicability of either thin-skinned or thick-skinned compressive styles in the Apennines of Italy. On the basis of two surface N–S cross-sections, integrated with recently acquired magnetotelluric data, the Matese structure appears as a single thrust sheet limited at the bottom by a low-angle thrust fault with sense-of-displacement towards the North. The structure was later deformed by footwall thrusts carrying Molise–Sannio Pelagic Basin Units and Apulian Carbonate Platform Units. The structure of the Matese Massif is composed mainly of Mesozoic carbonates of inner platform to by-pass and slope facies, separated within the thrust sheet by high-angle faults with low reverse horizontal displacement. These faults acted as normal faults in the Mesozoic and Cenozoic and controlled the carbonate facies distribution. During Neogene compression, these structures were tilted and then truncated by the basal short-cut thrust fault that cut from pre-Triassic units to Jurassic dolostone towards the foreland. Finally, Quaternary extensional tectonics dissected the whole structure with fault-related displacement values of up to 1000 m. This resulted in the present-day structural setting of the Matese Massif as a horst bounded to the SW and NE by fault-controlled basins, filled with continental deposits. This revised structural scenario is discussed within the framework of the structural style of external zones of the Apennines.

The Abruzzi–Molise sector in the Central Apennines is a part of a fold and thrust belt that has been deforming since the Late Cretaceous as a result of collision tectonics between the European and Adriatic plates. The superposition of different deformational styles highly reworked the originally complex palaeogeography of this portion of the southern Tethyan margin. Analogue modelling has been performed on thrusting mechanisms in the Abruzzi–Molise area in order to (1) reduce the number of admissible hypotheses regarding palaeogeographic setting, and (2) define thrusting mechanics. Both of these goals are crucial for hydrocarbon exploration purposes. The sandbox apparatus used to simulate the undeformed passive margin consisted of a thin compartment juxtaposed against a thick one along a linear boundary having variable geometries and mechanical stratigraphy; a rigid but mobile backstop was used to deform the stratigraphy in a Coulomb thrust wedge. Results from six experiments show that the geometric relationships between different structural units depend on the distribution of palaeogeographic domains. These domains are defined by mechanical and/or geometrical parameters, such as the orientation between the maximum compression direction and the palaeogeographic boundary, the mechanical stratigraphy and the thickness of the successions reproduced in the models. The present-day tectonic styles and Meso–Cenozoic palaeogeography of the Abruzzi–Molise area are discussed in terms of the mechanisms and structures analysed through the models.

A new seismotectonic model for the outer Central-Southern Apennines, including the epicentral area of the 2002 Molise seismic sequence, and adjacent foreland is proposed. The seismic sequence is related to foreland deformation affecting the Adriatic lithosphere. Such deformation is characterized by active NW–SE compression, resulting in the reactivation, mainly as dextral strike-slip faults, of pre-existing east–west oriented structures, both offshore and onshore. One of these structures is interpreted to extend westward and to reach the epicentral area of the recent earthquakes. NW–SE compression, ultimately related with Africa–Europe plate convergence, and uplift would essentially control the active tectonics of the analysed region.

The process of fault initiation by the coalescence of en-echelon arrays of tensile cracks has been discussed by several workers and is now well established. However, not many studies have tried to quantitatively describe this process in terms of displacement and shear strain that control the early stages of fault nucleation. In this study, a large number of conjugate en-echelon vein arrays showing extensional offsets have been analysed. These structures are exposed in well bedded micritic limestones deformed at very low-grade conditions in the Apennine mountain belt of southern Italy. Three different types of structures can be distinguished: (i) ‘brittle–ductile’ shear zones, characterised by arrays of en-echelon, calcite-filled tension gashes; (ii) shear zones showing incipient development of discontinuous shear-parallel fractures cutting through the vein array; and (iii) faulted shear zones, in which a continuous, discrete normal fault breaks through—and clearly developed from—an original en-echelon vein array. Critical values of displacement and shear strain have been determined for the onset of normal fault nucleation from ‘brittle–ductile’ shear zones, therefore suggesting that these parameters exert a major control on fault initiation. A diagram of shear zone population vs. displacement also shows that this parameter obeys a power law of the type generally followed by normal faults in the frictional regime. Our results suggest that, during the early stages of fault nucleation, displacement and shear strain control the switch from dominant ductile (viscous) deformation mechanisms—accompanied by brittle fracturing responsible for vein formation—to the frictional regime.

An integration of seismological data with geological and geomorphological information aided by seismic interpretation was performed to characterise the Quaternary tectonic evolution of the Metauro River basin area (northern Marche) and adjacent off-shore sector of the external Northern Apennines. On-shore, along the Adriatic coast, the youngest age of thrusting and folding post-dates the Early-Middle Pliocene, while Pleistocene deposits appear to be, at least in part, not involved in the deformation. Recent (i.e. post-thrusting) tectonic structures have been recognised both in pre-Quaternary substratum rocks and in Upper Quaternary continental deposits (Upper Pleistocene terrace alluvium, Upper Pleistocene–Holocene slope deposits). These faults are all compatible with a WSW–ENE oriented extension. In the Metauro River basin area, preserved flights of stream terraces have been categorised according to the presence or absence of alluvial suites in relationship to each terrace level. Here, based on both the heights above the valley floor and the areal distribution of stream terraces, a generalised vertical tectonic uplift can be inferred, particularly during the Middle–Late Pleistocene. Moreover, the along-valley distribution of stream terraces provides further constraints on the age of thrusting and folding. In fact, the reconstructed terrace-levels are substantially parallel, and no evidence for any significant deformation by fold activity has been recognised. Local deformation displayed by both terrace surfaces and alluvial/slope-waste deposits suggests, instead, the intervening of some minor differential movements associated with the generalised uplift and/or to Middle–Late Pleistocene normal faulting. Their occurrence appears anyhow to be unrelated with the pattern of folds and associated thrusts. The present-day seismic activity of the study area was considered by analysing 83 seismic events that occurred from 1987 to 2000. The epicentre distribution is very scattered, and depths are generally comprised within the first 20 km of the crust, clustering between 0 and 15 km. Most of the events have magnitude

The active geodynamic setting of the Northern Apennines is characterised by extension in the axial zone of the chain, and by a more complex tectonic behaviour in the frontal part of the belt. In the latter sector, moderate seismicity occurs, displaying compressional, strike-slip and extensional focal plane solutions with variably oriented P and T axes. For this area, a review of available geological and geophysical data has been integrated by the analysis of seismic reflection lines calibrated with deep well logs. This study confirms that, as already suggested by some previous workers, thrusting and related folding in the study area ceased in Early Pleistocene times. This feature is in contrast with the hypothesis of active thrusting related to a subducting lithospheric slab beneath the chain—an issue which is largely debated based on available geophysical information. Our analysis shows that the Northern Apennines are characterised by an active tectonic setting which is similar to that of the central and southern portions of the belt. These areas all display a Late Quaternary inactivity of the thrust front. NE–SW oriented extension (perpendicular to the strike of the orogen) is well established in their axial zones, whereas a less homogeneous stress field characterises their external sectors and the adjacent foreland. Within this framework, the seismotectonic behaviour of the Northern Apennines—and probably of the whole Italian peninsula between the Po Plain and the Southern Apennines (north of the Calabrian Arc)—may be interpreted as essentially controlled by two main processes. The first of them involves tectonic uplift, possibly related with slab detachment and associated unbending of the foreland plate. The second process consists of a present-day northwestward motion of the Adria block with respect to stable Europe.

In the Apennine fold and thrust belt of Italy, «thin-skinned» (i.e. detachment-dominated) and «thick-skinned» (i.e. crustal ramp-dominated) structures coexist, but with marked differences in both time and space. The external part of the northern Apennines and the deeper and younger portions (buried Apulian carbonates) of the thrust belt in the central and southern Apennines show limited amounts of shortening (in the range of 5–14 km). These result from similar deformation styles, involving the occurrence of relatively low-displacement, thick-skinned thrust ramps. The latter represent, at least in the northern Apennines, preexisting basement structures reactivated and inverted during contractional deformation. Interposed between the northern and southern parts of the fold and thrust belt, the central Apennines appear to constitute a transitional area in which strike-slip tectonics is relevant and carbonate platform units become predominant over pelagic basin ones, whereas the overall structure of the thrust belt becomes similar to that of the southern Apennines. In the latter, a peculiar structural style is revealed by the integrated analysis of surface and subsurface data. Structurally, the upper part of the thrust belt consists of allochthonous units made of Mesozoic peritidal carbonate platform and pelagic basin successions, and of Miocene foredeep sediments. These are completely detached from their original substratum and transported onto the 6–7 km thick, foreland carbonates of the Apulian platform. Based on available seismic data, the latter appears to be involved, together with the underlying Permo-Triassic clastics and, we infer, also the basement, in relatively low-displacement, thick-skinned structures. Therefore, in the southern Apennines, a transition from thin-to thick-skinned tectonics appears to have occurred through time. Thin-skinned structures characterise the shallower — and older — part of the thrust belt made of detached units, while a thick-skinned tectonic style is dominant in the buried Apulian carbonates of most recent accretion. The present boundary between the two different, superposed portions of the thrust belt consists of a low-angle, large-displacement thrust fault penetrated by numerous oil wells. Different styles and modes of contractional deformation in the investigated sectors of the Apennines appear to result from the geometrical requirement of maintaining strain compatibility and overall displacement continuity along a highly segmented orogen characterised by variable mechanical stratigraphy and southward increasing amounts of shortening.