The Matese-Sannio region in Southern Italy represents a crucial sector to analyse the processes that characterized the formation of Apennines and its current structural setting. This area is also of great interest from a seismotectonic point of view, hosting the epicentres of multiple historic destructive earthquakes.Our study presents part of the results of a multidisciplinary project (MOSAICMO) that integrates multiscale approaches to produce: a regional-scale model of this part of the orogen, a detailed reconstruction of the shallow subsurface of the Quaternary Bojano intramountain basin located in the central part of the study area, and detailed seismological and geophysical analyses.In this work, we present the 3D subsurface reconstruction of the Matese-Sannio region, exploring the orogen structure to a depth of ca. 10 km by using a dense network of seismic reflection profiles tied with well-logs drilled for hydrocarbon exploration.We tested the reliability of our geological reconstruction by performing numerical kinematic forward models that provide independent geometrical and temporal constraints to our conceptual model. We then compared our results with previous paleogeographic reconstructions of this sector of the Apennines to shed light on the complex interaction among different paleogeographic domains insisting in a relatively limited region.Our results provide an updated picture of the present-day structure of the transition between Central and Southern Apennines and represent a reference framework for more detailed applications within the MOSAICMO project.

The Middle Miocene- late Pliocene tectonic evolution of the Tuscan Shelf (northern Tyrrhenian Sea) between Elba Island and Monte Argentario Promontory is re-defined by the re-interpretation of vintage seismic profiles. The location and first evolution of Neogene sedimentary basins in those areas were controlled by structural inheritance since they developed on top of major thrusts before and during the Tyrrhenian Sea formation. Successive minor crustal extension contributed to today's structural setting and basin geometries. Using forward kinematic modeling, the geometrical validation of the seismic transects is presented here. The geometrical validation has been tied to the Martina-1 and Mimosa-1 wells, and the forward models have been successively compared with the geologic constraints derived from the available regional-scale geologic information (geological maps and literature data). Complete forward modeling from the Miocene to the late Pleistocene is forwarded along with an estimation of crustal shortening and extension that may account for the observed geometries of the seismic horizons and the modern basin geometries.

A reinterpretation of the vectorized version of public vintage seismic profiles in the Tyrrhenian Sea (Italy), between Elba Island and Monte Argentario promontory, was performed to reappraise the Tuscan shelf tectonic evolution. Despite the almost flat geometry of the seafloor, seismic profiles show a corrugated morphology of the pre-neogenic deformed acoustic basement, organized in structural highs and narrow, mostly N-S and NNW-SSE basins. We identified an intimate relationship between the thrust-related structural highs and the position of the basins, principally located at the forelimb and backlimb of major antiforms, a legacy of a primarily Miocene compressional stage. During the middle Miocene, the Tyrrhenian Sea opening set up, and the extensional front migrated from west to east, progressively activating and deactivating the observed high-angle faults, blandly controlling the sedimentation within the basins. After the late Messinian, a regional collapse stage led to the deepening and widening of the basins. A progressive deactivation of all the normal faults is recorded from the lower Pliocene. After the Late Pliocene/early Pleistocene, the area turned into a passive and widespread sinking stage without any frank tectonic activity. Results show that regional thrusts shaped the main architecture of the Tuscan Shelf shallow crust, while the neogenic depocenters started to develop as thrust-top basins along the flanks of the inherited antiforms. Intriguingly and partially in contrast with previous works, no evidence of low-angle normal fault was observed. We propose an innovative model that poses new questions on the crustal-scale mechanisms responsible for Tyrrhenian extensional process-related features, also establishing a new and unique starting point for fully unraveling the tectonic evolution of this portion of central Italy's offshore domain.

The Amatrice (Mw 6.0) - Visso (Mw 5.9) - Norcia (Mw 6.5) seismic sequence (hereafter AVN) struck the Central Apennines (Italy) in 6-7 months during 2016-2017, and it has been widely associated with fluid migration in the normal faults network. The analysis of attenuation parameters (e.g., scattering and absorption) gives information about material properties and the presence of fluids and fracturing. In this study, we investigate in a 3D mapping the scattering contribution to the total attenuation of the AVN seismic sequence (August 2016-January 2017), together with a pre-sequence dataset (March 2013-August 2016). We applied peak delay as a proxy of seismic scattering, to obtain further information on the fracturing processes in time and space. Previous 2D mapping of peak-delay time and coda attenuation tomography in the same study area indicated a substantial control on the scattering of seismic waves by structural (e.g., Monti Sibillini thrust) and lithological (e.g., Umbria- Marche and Lazio-Abruzzi geological domains) features.Our 3D results show clear differences between the pre-sequence and the sequence, where we can identify an increase of scattering with time after the mainshocks. The substantial alterations in scattering are observed between 4 - 6 km depth, in the hanging wall of the Monti Sibillini thrust, which acts as a rheological barrier between high and low scattering zones. Peak delay variations detected a significant anomaly in the Triassic deposits layer, at the roots of the Acquasanta thrust, east of Monti Sibillini. Here, low scattering during the pre-sequence epoch is replaced by high scattering during the mainshocks. The low scattering along the Acquasanta thrust suggests an increment of pore pressure, associated with the presence of fluids in this geological formation. The subsequent release of those fluids may have caused the mainshocks of the seismic sequence, and a subsequent increase in fracturing, as observed by the high scattering anomaly. These results bring a new light on the importance to consider the thrusts systems in the tectonic framework of the Central Italy.

Abstract Deep fluid circulation likely triggered the large extensional events of the 2016–2017 Central Italy seismic sequence. Nevertheless, the connection between fault mechanisms, main crustal‐scale thrusts, and the circulation and interaction of fluids with tectonic structures controlling the sequence is still debated. Here, we show that the 3D temporal and spatial mapping of peak delays, proxy of scattering attenuation, detects thrusts and sedimentary structures and their control on fluid overpressure and release. After the mainshocks, scattering attenuation drastically increases across the hanging wall of the Monti Sibillini and Acquasanta thrusts, revealing fracturing and fluid migration. Before the sequence, low‐scattering volumes within Triassic formations highlight regions of fluid overpressure, which enhances rock compaction. Our results highlight the control of thrusts and paleogeography on the sequence and hint at the monitoring potential of the technique for the seismic hazard assessment of the Central Apennines and other tectonic regions.

Abstract. The Po Plain (Italy) is one of the most densely populated and productive regions of Europe, characterized by a flourishing economy (also linked to strategic subsurface resources) and several world cultural and natural heritage sites. The coupling of socio-economic interests with geological hazards (i.e. seismic, subsidence, and flooding hazards) in this area requires accurate knowledge of the subsurface geology, the active geological processes, and the impact of human activities on natural environments to mitigate the potential natural and anthropic risks. Most data unveiling the subsurface geology of this region were produced by the hydrocarbon exploration industry. Indeed, the Po Plain hosts many hydrocarbon fields that have been discovered since the early 1950s, giving rise to the subsurface exploration through extensive seismic reflection surveys and drilling of numerous deep wells. In this work, geological and geophysical data from 160 deep wells drilled for hydrocarbon exploration and/or exploitation purposes in the Po Plain and in the facing northern Adriatic Sea have been collected and digitized along with several published geological cross-sections and maps. These data have been used to reconstruct the overall subsurface 3D architecture and to extract the physical properties of the subsurface geological units. The digitized data are suitable to be imported into geo-software environments so as to derive the geophysical and mechanical properties of the geological units for a wealth of applied and scientific studies such as geomechanical, geophysical, and seismological studies. The integrated dataset may represent a useful tool in defining regional first-order strategies to ensure the safety of the urbanized areas and human activities and to reduce natural and anthropic risks that may affect this crucial region of Europe. In particular, the data collected would be useful to highlight sensible areas where data collection and more detailed studies are needed. Nowadays, such issues are particularly relevant for the underground industry development related to the increasing interest in possible CO2 and hydrogen underground storage, which can play a fundamental role in the energy transition process towards decarbonization goals. The full dataset is available at the following link: https://doi.org/10.5281/zenodo.8126519 (Livani et al., 2023).

<p>The undersea portion of the Northern Apennines is characterized by blind thrust faults running parallel to the Adriatic Sea coastline in northeastern peninsular Italy. These thrusts are buried below a thick cover of syntectonic Quaternary deposits. Their elusive geological signature at shallow depths and the low seismicity associated with them gave rise to diverging interpretations and views concerning the current activity of these thrusts and their earthquake potential.</p> <p>On 9 November 2022, a seismic sequence started with an Mw 5.5 earthquake in the Pesaro Offshore. Hypocentral depth, focal mechanism, and aftershocks location all suggest that the earthquake was generated by one of the outermost thrusts of the Northern Apennines front that was already mapped as a potential seismogenic source in the DISS database (https://diss.ingv.it/diss330/sources.php?ITCS106).</p> <p>We present a 3D reconstruction of the thrust system that caused the Pesaro Offshore seismic sequence obtained through the reinterpretation of publicly available seismic reflection profiles and well logs. The 3D geometry and size of the thrust activated during the seismic sequence suggest that it can also host larger earthquakes. We also present the application of a well-established workflow for calculating the slip rates of this buried thrust already tested in nearby structures. The outcomes of this study represent a step forward for earthquake and tsunami hazard models, the study of the seismic source, the enhancement of earthquake location by mix and match of seismological and geological independent data, and the expected kinematics of future potential earthquake ruptures.</p> <p>These results are particularly relevant in offshore areas, where neither surface co-seismic ruptures nor GPS/InSAR deformation data are available in the aftermath of a significant earthquake. In these cases, multichannel seismic reflection profiles represent the only tool to appraise the subsurface structural setting. </p>

Abstract The prompt identification of faults responsible for moderate‐to‐large earthquakes is fundamental for understanding the likelihood of further, potentially damaging events. This is increasingly challenging when the activated fault is an offshore buried thrust, where neither coseismic surface ruptures nor GPS/InSAR deformation data are available after an earthquake. We show that on 9 November 2022, an Mw 5.5 earthquake offshore Pesaro ruptured a portion of the buried Northern Apennines thrust front (the Cornelia thrust system [CTS]). By post‐processing and interpreting the seismic reflection profiles crossing this thrust system, we determined that the activated fault (CTS) is an arcuate 30‐km‐long, NW‐SE striking, SW dipping thrust and that older structures at its footwall possibly influenced its position and geometry. The activation of adjacent segments of the thrust system is a plausible scenario that deserves to be further investigated to understand the full earthquake potential of this offshore seismogenic source.

The Val d’Agri (VA) oilfield in the Lucanian Apennines (southern Italy), represents the largest onshore in Europe. Since the 1990's, hydrocarbons are produced from a fractured carbonate reservoir with an average extraction rate of 7*104 barrels/day of oil and 3*106 Smc/day of gas. Part of the wastewater has been re-injected since 2006 into a marginal portion of the reservoir by a high-rate well (Costa Molina 2, CM2). Charged by the Italian oil and gas safety authority, the National Institute of Geophysics and Volcanology (INGV) monitors the VA industrial hydrocarbon operations through the research activity of a dedicated working group (CMS, Centro di Monitoraggio del Sottosuolo) and according to the governmental monitoring guidelines. The CMS operates the real-time acquisition and offline analyses of seismic data recorded at 56 seismic stations associated with public and private local seismic networks. The principal aim of the CMS is to investigate the risk associated with industrial activities that can induce or trigger seismic events by producing stress changes within the upper crustal volume. Previous works have highlighted a spatio-temporal relationship between micro-seismicity (ML ≤ 2.2) and wastewater injection, delineating a NE-dipping back-thrust near the CM2. Part of the microseismicity recorded in the southwestern portion of the VA has also been associated with the water level changes of the Pertusillo lake. One of the main challenges is to define an accurate structural setting of the VA to understand the potential of earthquakes in the area and investigate the presence of active faults. The VA consists of a Quaternary extensional tectonic basin and it is one of the areas of highest seismic hazard in Italy (Basilicata, 1857, M7 earthquake). The basin is bounded by two parallel and oppositely dipping normal fault systems: the Monti della Maddalena Fault System (MMFS) on its western side and the Eastern Agri Fault System (EAFS) on the eastern one. The characterization of the ongoing tectonic activity of the MMFS and EAFS, and their hierarchical relationship is still generating debate among the scientific community. We adopt a multidisciplinary approach based on detailed geological-structural, geophysical and seismic analyses, and electrical resistivity tomography, aimed at reconstructing the subsurface geology of the area and recognizing and characterizing the active and capable faults, and the associated potential for local seismic hazard. We present and discuss the results of this work, focusing on the relative location of seismic events that occurred between March and June 2022. The outcomes allow inferring interesting geologic constraints, highlighting the relationships between the distribution of local seismicity and the structural setting of the area in the uppermost crust (depth < 6 km).

The refraction reprocessing of the CROP11-1999 seismic reflection data, which were acquired for deep seismic exploration using a split-spread long offset geometry, provides valuable new insights into the main geological structures of the central Apennines. In this study, we present the geophysical interpretation of a sub-transect of the CROP11 seismic profile, crossing the Piani Palentini and Fucino basins carried out using an integrated approach based on the refraction tomography, the stacked refraction convolution section, and the seismic reflection. The reprocessing allowed us to obtain, for the first time, a high resolution (about 15 m in distance and depth) P-waves seismic velocity 2D model and the imaging of the refractor interface of the basin up to the depth of the Meso-Cenozoic carbonate substratum. The outcomes, combined with the interpretation of a CROP11 seismic reflection sub-transect and a subparallel commercial seismic reflection profile, allowed us to highlight a complex basin-fill architecture and stratigraphy. Four seismo-facies, characterized by different Vp velocity values, were recognized above the Meso-Cenozoic carbonate substratum. In particular, a low-velocity zone (LVZ) was evidenced in both basins. The geophysical interpretation and the comparison with the outcropping se-quences allowed us to associate it with an upper Messinian thrust-top deposit.The obtained model constitutes an essential geophysical-geological informative base for future investigations on seismic wave propagation and site response studies at the large scale of the Fucino Basin, one of the areas of the Italian territory with a high seismic hazard.

Vintage seismic reflection data can be of great value for both scientific and commercial communities. Although they often have reduced quality compared to modern data, due to the old acquisition equipment and limited processing techniques, such datasets constitute a valuable resource, for example, in areas with no recent coverage or with current limitations for environmental protections or restrictions in obtaining exploration permits. The fact that old paper seismic profiles can now be converted successfully into usable format (SEG-Y), readable by modern processing and interpretation software, makes them an even more valuable resource. This chapter illustrates a case study from the eastern Tyrrhenian margin (Italian offshore), where vintage seismic profiles and well data from the ViDEPI public database were rescued and reused for research purposes. Digital SEG-Y files were created from old paper sections, and these were interpreted to unravel the stratigraphic and structural architecture of the offshore sedimentary basins. Despite the dated seismic dataset, the main evolutionary tectonic steps affecting the area were outlined, proving the still relevant value of such datasets. Considering important current topics such as environmental issues, funding difficulties, data accessibility, this kind of data represent a valuable heritage for the scientific community to rescue and exploit.

This work presents the first 3D geological model of the Rome coastal area that integrates available subsurface geological, stratigraphic and geophysical data with surface geochemical data obtained both from the literature and new surveys. The model provides new insights into the stratigraphic and tectonic setting of the area and the geological factors controlling both natural and human-induced gas emissions. This sector of the Italian Tyrrhenian margin has been historically affected by natural emissions of deep CO2 and thermogenic CH4, stored in permeable layers but with local migration to the surface along buried normal faults. In addition to natural processes, human activities can also cause leakage and serious health risks, such as the abrupt gas release in August 2013, that was triggered by borehole drillings near the Rome international airport. The presented 3D reconstruction unveils the link between faults, stratigraphy, lithology and the distribution of the soil gas anomalies. It provides information about the depth of the reservoir that can potentially trap endogenous gases, and the location and geometry of the main faults along which the gas migrates towards the surface. Furthermore, reconstruction of the distribution and thickness of important clay layers better constrains the low permeable areas that prevent gas escape. The 3D model, coupled with the geochemical information, can serve as a useful tool for the local administration to perform land-use planning and manage the local geological and degassing hazards that affect this highly urbanized area near Rome. Furthermore, we estimate that the large amount of CO2 broadly released in the area also provides a contribution to the budget of natural greenhouse gases in the atmosphere.

Bedding-perpendicular joints striking parallel (longitudinal) and perpendicular (transverse) to both the axis of the hosting anticline and the trend of the foredeep-belt system are widely recognized in fold-and-thrust belts. Their occurrence has been commonly attributed to folding-related processes, such as syn-folding outer-arc extension, although they can also be consistent with a pre-folding foredeep-related fracturing stage. Here we report the pre-folding fracture pattern affecting the Pietrasecca Anticline, in the central Apennines (Italy), resolved by a detailed field structural analysis. Field observations, scan-lines and interpretation of virtual outcrops were used to study the intensity, distribution and the orientations of fracture pattern along the anticline. The fracture pattern of the Pietrasecca Anticline consists of longitudinal and transverse joints, oriented approximately perpendicular to bedding, and of a pre-folding longitudinal pressure-solution cleavage set, which is oblique to bedding regardless of the bedding dip. Cross-cutting relationships show that joints predated the development of the pressure-solution cleavage. Furthermore, joint intensity does not relate to the structural position along the anticline. Taken together, these observations suggest that jointing occurred in a foredeep environment before the Pietrasecca Anticline growth. Our work further demonstrates that joints striking parallel and orthogonal to the main fold axis do not necessarily represent syn-folding deformation structures.

The reconstruction of the hydrocarbon migration and entrapment history is fundamental for reducing risks and identifying traps and migration pathways during oil exploration and exploitation in fold-and-thrust belts, which host 14% of the world's discovered oil reserves. Within fold-and thrust belts, faults and folds have fundamental roles in controlling hydrocarbon migration, entrapment, and/or leakage. Past studies have mainly focused on the role of syn-orogenic thrusts, tear faults, and folds in controlling hydrocarbon migration and entrapment. On the contrary, little attention has been dedicated to the role of normal faults in hydrocarbon remobilization during the post-orogenic extension. We combine field and subsurface data with geological evidence from the Ripi oil field, central Apennines (Italy), and propose a conceptual model for hydrocarbon remobilization along post-orogenic normal faults and potential entrapment within shallow reservoirs. Results show that post-orogenic normal faults promoted up-dip hydrocarbon remobilization from oil traps generated during fold-and-thrust belt development. Where pre-orogenic deposits are still covered by syn-orogenic deposits, hydrocarbons moved up-dip along postorogenic normal faults and impregnated high-porosity sandstone lenses, generating discontinuous and heavy oil reservoirs. On the contrary, where syn-orogenic deposits were eroded in response to orogenic uplift, hydrocarbons leaked at the Earth's surface. Results from this study can be applied to reduce risks during hydrocarbon exploration and appraisal in similar tectonic settings, such as Hellenides and Carpathian fold-and-thrust belts, as well as the southern Apennines of Italy, where the Tempa Rossa and Monte Alpi oil fields, two of the largest onshore oil fields in Western Europe, were discovered in the last decades.

The volcano-hosted geothermal system of Copahue is one of the most promising resources of renewable energy in Argentina. It is driven by a layered reservoir composed of a steam cap above a deep liquid-dominated reservoir. We study the surficial leakages of the shallow steam zone by performing a discrete fracture network model and a 3D forward strain-stress model of the upper caprock unit. The hydrothermal zones linked to steam cap leakages are subordinated to deep-rooted N60-striking faults. Associated damage zones exhibit higher values of fracture intensity, vertical and anisotropy of permeability than the host rocks. Joints and cross-joints likely control leakage zones, where the formers are subject to high dilation tendency. The Anfiteatro monocline might constitute the northwestern boundary of the shallow steam zone. Variations of H2O–CO2 ratio, helium isotopic signature, and CO2 between hydrothermal zones are explained in terms of petrophysical properties of the upper ignimbrites and changes in their structural control. Our results suggest that the upper caprock ignimbrite avoids the decompression of the reservoir because it provides the low fractured and low permeability layer that seals the geothermal system; conversely, ignimbrites affected by the extensional faults system enhance the shallow vapor zone given its high fracture density and permeability.

The Adria microplate is the foreland of the oppositely verging Apennines and Alps or Dinarides fold-thrust belts associated to the related subduction zones. Along its western margin, the Adria plate hosts the active Northern Apennines accretionary prism, which is buried under the Adriatic Sea and the Po Plain. The interpretation of seismic reflection profiles and borehole data allowed us to define the geometry of the transition from the Apennines fold-thrust belt to its undeformed foreland. Moreover, continuous GPS (CGPS) data from offshore hydrocarbon platforms anchored to the seabed of the northern Adriatic plate allow to measure present-day kinematics. Although the CGPS signals are affected by non-tectonic components associated with hydrocarbon extraction, the integration of geodetic analysis, subsurface geological reconstructions, and analytical modeling allowed us to constrain the ongoing tectonic activity. Shortening is currently accommodated by aseismic slip along the basal detachment, likely accumulating elastic energy along the frontal ramp that may eventually seismically slip. Our multidisciplinary study suggests that the study area may not be sheltered from relevant seismic sequences similar to the Mw 6 Emilia 2012 events and that the occurrence of potential seismogenic sources in the area should be carefully evaluated. Similar studies may be useful to constrain the present-day activity in other marine areas and to identify potential and hitherto unrecognized seismogenic sources along the entire Apennines belt and other accretionary prisms worldwide.

Cap rock characterization of geothermal systems is often neglected despite fracturing may reduce its efficiency and favours fluid migration. We investigated the siliciclastic cap rock of Rosario de La Frontera geothermal system (NW Argentina) in order to assess its quality as a function of fracture patterns and related thermal alteration. Paleothermal investigations (XRD on fine-grained fraction of sediments, organic matter optical analysis and fluid inclusions on veins) and 1D thermal modelling allowed us to distinguish the thermal fingerprint associated to sedimentary burial from that related to fluid migration.The geothermal system is hosted in a Neogene N-S anticline dissected by high angle NNW- and ENE-striking faults. Its cap rock can be grouped into two quality categories:rocks acting as good insulators, deformed by NNW-SSE and E-W shear fractures, NNE-SSW gypsum- and N-S striking calcite-filled veins that developed during the initial stage of anticline growth. Maximum paleo-temperatures (<60 degrees C) were experienced during deposition to folding phases.rocks acting as bad insulators, deformed by NNW-SSE fault planes and NNW- and WNW-striking sets of fractures associated to late transpressive kinematics. Maximum paleo-temperatures higher than about 115 degrees C are linked to fluid migration from the reservoir to surface (with a reservoir top at maximum depths of 2.5 km) along fault damage zones.This multi-method approach turned out to be particularly useful to trace the main pathways of hot fluids and can be applied in blind geothermal systems where either subsurface data are scarce or surface thermal anomalies are lacking. (C) 2016 Elsevier B.V. All rights reserved.

This study presents new stratigraphic, structural and hydrogeological data on the Tocomar geothermal volcanic area (Puna plateau, Central Andes, NW Argentina), together with preliminary geochemical and magnetotelluric data. The main geothermal reservoir is located within the fractured Pre-Palaeozoic-Ordovician units. The reservoir is recharged by meteoric waters. Geothermal fluids upwell where main regional structures intersect secondary structures associated with the development of the Tocomar basin. Preliminary data indicate a reservoir temperature of similar to 200 degrees C and a local geothermal gradient of similar to 130 degrees C/km associated with the Quaternary volcanic activity in the Tocomar area. (C) 2016 The Authors. Published by Elsevier Ltd.