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The active Campi Flegrei caldera in southern Italy has a remarkably long history of coexistence between volcanism and human settlements, and it is famous for its peculiar slow ground movement called bradyseism, i.e. episodes of inflation and deflation of the caldera floor due to magmatic and/or hydrothermal processes. This natural phenomenon has interacted with the civilization that inhabited this strategic and fertile area, especially in Roman times, when the sinking of the coast hindered the flourishment of Puteoli and Baiae coastal towns. The drowning of a large part of Republic-early Imperial Roman coastal buildings, west of the modern Pozzuoli town, is classically used to illustrate the bradyseism activity. In this paper, we investigate the spatial variability and the role of this phenomenon, demonstrating that the caldera deflation alone cannot account for the submersion of Roman facilities in the western sector where the harbour structures of Portus Iulius and luxury villas of the Baianus Lacus presently lie beneath sea level. On the contrary, the sinking of this area is mainly the result of the activity of volcano-tectonic faults. We restored the topography to 100 BCE using archaeological and high-resolution topographic data. Results show that the several metres of vertical displacement recorded in the Baia area in the last 2100 yr were mainly produced by the activity of normal faults and secondarily by caldera deflation, the former including the long-lived Baia Fault and the younger normal faults associated with the Monte Nuovo eruption at 1538 CE. [ABSTRACT FROM AUTHOR]

We report the occurrence of several sand liquefaction structures, such as sand dikes, in the stratigraphic record of the Campi Flegrei volcano, located both inside and outside the caldera. Five sites were analyzed within the caldera and two outside. The grain size analysis of the sand fillings indicates that these deposits are very fine-to-coarse sands generally poorly sorted. All of the granulometry curves fall within the field of the liquefiable, loose sediments. Frequently, dikes are characterized by two fillings: a rim showing poorly sorted finer sands and a core with extremely poorly sorted coarser sediments. We suggest that seismic-related liquefaction processes triggered the injection of these sand dikes during unrest episodes in the last 15 kyr. In particular, the sand dikes located outside the caldera, characterized by larger thicknesses and lengths, mark an important extensional episode, probably associated with the caldera formation during the Neapolitan Yellow Tuff eruption at 15 ka. Furthermore, liquefaction structures within the caldera are related to the seismic activity, probably occurring during the Agnano–Monte Spina caldera formation and the volcano-tectonic ground deformation, predating Epoch 3b (4.3 ka) and the Monte Nuovo (1538 CE) eruptions. This study highlights that these seismic-related liquefaction structures are common within the volcanic record of the Campi Flegrei, suggesting that the sand source can be both the widespread marine succession underlying the Epoch 3 deposits in the caldera central sector and the primary ash layers extensively present in the volcanic record. [ABSTRACT FROM AUTHOR]

Silicic calderas are volcanic systems whose unrest evolution is more unpredictable than other volcano types because they often do not culminate in an eruption. Their complex structure strongly influences the post‐collapse volcano‐tectonic evolution, usually coupling volcanism and ground deformation. Among such volcanoes, the Campi Flegrei caldera (southern Italy) is one of the most studied. Significant long‐ and short‐term ground deformations characterise this restless volcano. Several studies performed on the marine‐continental succession exposed in the central sector of the Campi Flegrei caldera provided a reconstruction of ground deformation during the last 15 kyr. However, considering that over one‐third of the caldera is presently submerged beneath the Pozzuoli Gulf, a comprehensive stratigraphic on‐land‐offshore framework is still lacking. This study aims at reconstructing the offshore succession through analysis of high‐resolution single and multichannel reflection seismic profiles and correlates the resulting seismic stratigraphic framework with the stratigraphy reconstructed on‐land. Results provide new clues on the causative relations between the intra‐caldera marine and volcaniclastic sedimentation and the alternating phases of marine transgressions and regressions originated by the interplay between ground deformation and sea‐level rise. The volcano‐tectonic reconstruction, provided in this work, connects the major caldera floor movements to the large Plinian eruptions of Pomici Principali (12 ka) and Agnano Monte Spina (4.55 ka), with the onset of the first post‐caldera doming at ca. 10.5 ka. We emphasise that ground deformation is usually coupled with volcanic activity, which shows a self‐similar pattern, regardless of its scale. Thus, characterising the long‐term deformation history becomes of particular interest and relevance for hazard assessment and definition of future unrest scenarios. [ABSTRACT FROM AUTHOR]

Accurate digital elevation models represent the basic tool for a large spectrum of applications, including geological, architectonic, archaeological, and urbanistic studies. However, aggressive urbanization may significantly alter the morphology of areas of interest. Such is the case of the active Campi Flegrei caldera in southern Italy, where all the buildings, facilities, infrastructures, quarries, and landfills altered the original volcanic morphology. To avoid these limitations, we analyzed a set of vintage aerial photographs acquired in 1943 by Italy's Military Geographic Institute (IGM). We reconstructed the study area's topography before the deep anthropic modification from the 1960s onwards by applying Structure-from-Motion photogrammetric processing. On the reconstructed orthomosaic and a historical-Digital Surface Model (hDMS), we conducted geomorphic analyses along 18 longitudinal stream profiles outside, across the border, and inside the caldera, underlining that the rectilinear sections with preferred orientations and increased incision values suggest a strong structural underpinning on valley incision and stream paths. The analysis of the spatial distribution of sinuosity, SL index, Chi (χ) value and knickpoint maps suggests the presence of tectonic lineaments that influence the stream network from the pre-caldera (>40 ka) to recent times, producing articulated caldera and craters geometry as well as affecting the localization of volcanic vents. The comparison between the 1943 hDSM and 2013 LiDAR (Light Detection and Ranging) DSM allowed us to spotlight the areas that show the most significant differences due to anthropic intervention that obliterated critical features, thus supporting our motivation to use this base. Overall, the results indicate that long-lived volcano-tectonic and tectonic structures control the orientation of drainage patterns and their re-arrangements during volcano-tectonic deformation phases. Finally, a comprehensive structural map, based on the merged 1943 hDSM and the bathymetric DEM, is presented together with a conceptual evolutionary model of the stream network across the caldera border. Under the proper acquisition conditions, vintage aerial photographs can provide a useful tool for morphological analysis and can be applied to several topics in the geosciences. • The original topography of Campi Flegrei is restored using historical aerial photographs. • Several geomorphic indices highlight the activity of volcano-tectonic structures. • Rectilinear and deeply incised valleys occur in different sectors. • NE–SW and NW–SE oriented tectonic features are overprinted by E–W oriented features. • Tectonic lineaments control the occurrence of volcanism through time. [ABSTRACT FROM AUTHOR]

Models of volcanic collapses proposed in the literature rely on combining field examples with analogue and numerical modelling to connect superficial observables to sub-surface volcano-tectonic processes. However, the behaviour of such collapses in an already faulted and fractured medium needs to be better explored. We studied a complex array of normal and reverse faults within the central sector of the active Campi Flegrei caldera, where faults with centimeters-to-meters displacements are hosted in the La Pietra tuff (∼13.5 ka) and the overlying pyroclastic succession of the last ∼5.5 kyr. We analyzed the attitude, kinematics and throw of these structures, employing a UAV-based digital outcrop model. The analysis shows that antithetic normal and reverse faults form in the hanging wall of a pre-existing WNW striking, NNE-dipping master normal fault. Moving northward, the strike of the antithetic faults rotates from WNW to NNW directions, with the latter showing a right-lateral oblique component. The simultaneity and coherence of both kinematics and attitudes are verified by the throw analysis. We associated the formation of this array with the caldera-collapse phase of the Agnano-Monte Spina eruption (∼4.55 ka), which caused off-caldera faulting beyond the main collapsed area. Based on field data, we suggest that during peak caldera-forming phases, wider areas beyond the main caldera scarps can be involved in volcano-tectonic collapses in the presence of a pre-existing fault network and complex tapped reservoirs. This highlights the role of inherited structures in weakening the crust above the magma reservoir that can potentially increase the magnitude and duration of caldera-forming eruptions, as they may induce a broader roof rock subsidence, pressurizing wider regions of the sub-caldera magma system. • We studied a complex array of normal and reverse faults at Campi Flegrei caldera. • These faults occur in the hanging wall of a reactivated master normal fault. • Both normal and reverse faults accommodate the overall displacement. • The array formed during the Agnano Monte Spina Plinian eruption collapse phase. [ABSTRACT FROM AUTHOR]

In the past two decades, the central portion of Campi Flegrei caldera has experienced ground uplift up to 15 mm/month, with an increase of rate, magnitude and extent of the seismicity. In this work, we perform multi‐scale precise earthquake relocation of the 2014–2024 seismicity, mapping in detail activated fault zones. We relate the geometry, extent, and depth of these zones with up‐to‐date structural reconstructions of the caldera. The current seismicity is mainly driven by ground‐uplift‐induced stress concentration on pre‐existing, weaker fault zones, some of which identified for the first time. These structures are not only related to the inner caldera and dome resurgence but also to volcano‐tectonic events of the last 10 ka. The extent of imaged fault segments suggests they can accommodate ruptures up to a moment magnitude 5.1, significantly increasing seismic hazard in the area. Plain Language Summary: During the past 2 yrs, there has been a marked increase in ground uplift, number and size of earthquakes at Campi Flegrei caldera. This increase in activity has raised concerns among the population and public authorities about the impact of seismic activity on buildings and infrastructure in the area and about the best actions to undertake during the seismic emergency to reduce the risk. Additionally, the possibility of a future volcanic eruption is being considered, although currently geochemical and geophysical monitoring shows no unequivocal signs of precursory phenomena. In this work, we map the last decade of seismicity with a new technique providing high‐precision earthquake locations that allow us to unveil the currently activated fault zones of the inner caldera. The results show a near‐elliptical distribution of seismicity at the global scale of the caldera, which at a smaller scale delineates complex seismogenic structures. The size of imaged faults suggests that earthquakes up to a moment magnitude 5.1 can occur, significantly increasing seismic hazard in the area. Key Points: High‐precision location of 2014–2024 seismicity in Campi Flegrei depicts active fault zones with unprecedented detailSeismicity occurs along different volcano‐tectonic structures including the caldera inner ring fault zone and faults bounding the Solfatara craterA new structure has been recognized in the eastern sector of the caldera, hosting the largest magnitude event in the analyzed period [ABSTRACT FROM AUTHOR]

The structure of a caldera may influence its activity, making its understanding crucial for hazard assessment. Here, we analysed high-resolution seismic profiles in the Campi Flegrei (southern Italy) offshore sector. We recognised two main fault systems, including those associated with the formation of the caldera and those affecting the resurgent dome. The former system comprises three broadly concentric fault zones (inner, medial and outer ring fault zones) depicting a nested caldera geometry. Considering the relations between faults and seismic units that represent the marine and volcaniclastic successions filling the caldera, all ring faults were formed during the Campanian Ignimbrite eruption (40 ka) and subsequently reactivated during the Neapolitan Yellow Tuff eruption (15 ka). In this last caldera-forming event, the inner and medial fault zones accommodated most of the collapse and were episodically reactivated during the younger volcano-tectonic activity. The second fault system occurs in the apical zone of the resurgent dome and comprises dominantly high-angle normal faults that are mainly related to the volcano-tectonic collapse that followed the Agnano-Monte Spina Plinian eruption (4.55 ka). Finally, we provide a volcano-tectonic evolutionary model of the last 40 kyr, considering the interplay among ring and dome faults activity, volcaniclastic sedimentation, ground deformation and sea-level changes. • A detailed structural map of the offshore sector of Campi Flegrei caldera is provided. • Two main fault zones have been identified associated with the caldera ring faults and the resurgent dome faults. • The Neapolitan Yellow Tuff eruption reactivated the 2.5 km wide caldera fault zone of the Campanian Ignimbrite eruption. • The dome fault zone accommodated volcano-tectonic collapse during the Agnano-Monte Spina eruption. • Mapped faults controlled caldera deformation, volcanism distribution and hydrothermal fluid uprise in the last 40 kyr. [ABSTRACT FROM AUTHOR]

The present study aims at contributing to the structural framework and volcano-tectonic evolution of the Campi Flegrei caldera with a joint analysis of multi-scale seismic profiles in the Pozzuoli Bay, providing additional insights into the last ~15 ky of ground deformation.Only in recent years the submerged part of the caldera has been explored using marine geophysical data (Sacchi et al., 2014; Steinmann et al., 2016, 2018). Seismo-stratigraphic interpretation of the marine geophysical data revealed that, after the NYT eruption, rejuvenation of the activity occurred mainly along the ring faults while a resurgent central dome system was gradually developing. The shallowest seismo-stratigraphic interval has been calibrated by marine gravity cores which allowed to identify key horizons between the AD 1538 Monte Nuovo tephra to Nisida tephra ~3.9 ky. Chronostratigraphy of the deeper part of the caldera infill sequence has been inferred through tentative correlation with the most significant eruptions known on-land taking into account vent location, VEI, distribution of pyroclastic deposits and hiatuses developed during periods of relative volcanic rest (Smith et al., 2011; Steinmann et al., 2018). In addition to the volcano-tectonic events, the depositional environment has been affected by post-glacial sea-level rise as reconstructed by Lambeck et al. (2011). This work provides a first detailed map of faults developed on top of the resurgent dome and an improved characterization of the ring faults, on the southern side of the caldera. The apical faults of the dome have a complex pattern with NNE-SSW dominating trend. Since ~12 ky a total uplift of ~130 m is estimated between the post collapse un-deformed and dome-deformed markers.On the eastern side of the gulf has been defined timing and extension of a laccolite intrusion. On the western side, the Punta Pennata structure has been mapped and interpreted as a localized structure linked to magma migration in the footwall of the collapse ring fault.ReferencesLambeck, K., Antonioli, F., Anzidei, M., Ferranti, L., Leoni, G., Scicchitano, G., & Silenzi, S. (2011). Sea level change along the Italian coast during the Holocene and projections for the future. Quaternary International, 232(1-2), 250-257.Sacchi, M., Pepe, F., Corradino, M., Insinga, D. D., Molisso, F., & Lubritto, C. (2014). The Neapolitan Yellow Tuff caldera offshore the Campi Flegrei: Stratal architecture and kinematic reconstruction during the last 15 ky. Marine Geology, 354, 15-33.Smith, V. C., Isaia, R., & Pearce, N. J. G. (2011). Tephrostratigraphy and glass compositions of post-15 kyr Campi Flegrei eruptions: implications for eruption history and chronostratigraphic markers. Quaternary Science Reviews, 30(25-26), 3638-3660.Steinmann, L., Spiess, V., & Sacchi, M. (2016). The Campi Flegrei caldera (Italy): formation and evolution in interplay with sea-level variations since the Campanian Ignimbrite eruption at 39 ka. Journal of Volcanology and Geothermal Research, 327, 361-374.Steinmann, L., Spiess, V., & Sacchi, M. (2018). Post-collapse evolution of a coastal caldera system: Insights from a 3D multichannel seismic survey from the Campi Flegrei caldera (Italy). Journal of Volcanology and Geothermal Research, 349, 83-98. [ABSTRACT FROM AUTHOR]

Our research focuses on the reconstruction of turbidity paleocurrents of the Cilento Group in the Cilento area (southern Apennines, Italy). These deposits were formed in the wedge-top basin above the oceanic Ligurian Accretionary Complex, the early orogenic wedge of the southern Apennines. The Cilento Group succession, whose age ranges between the uppermost Burdigalian and lowermost Tortonian, consists of a thick pile of sandstones, conglomerates, marls and pelites grouped in two formations (Pollica and San Mauro Fms). We retrieved information on the turbidity current directions through sedimentary features such as flute and groove casts, flame structures and ripple marks. The aim of this study is to shed light on the early tectonic evolution of the southern Apennines by reconstructing the geometry of this basin, the source areas that fed it and the paleogeography of the central Mediterranean area in the Miocene. We analyzed 74 sites in both formations and collected 338 measurements of paleocurrent indicators. Because the succession was affected by severe thrusting and folding, every paleocurrent measurement was restored, reinstating the bedding in the horizontal attitude. Results indicate a complex pattern of turbidity current flow directions consistent with a basin model fed by a spectrum of sources, including recycled clasts from the Ligurian Accretionary Complex, Calabria–Peloritani Terrane and the Apennine Platform units and volcaniclastics from the synorogenic volcanoes located in the Sardinia block. [ABSTRACT FROM AUTHOR]

Faults in volcanic areas can have different origins and can form due to several volcano-tectonic processes. In this work, by means of detailed field observations, we analysed a fault array cutting through a recent pyroclastic succession in the Campi Flegrei caldera of southern Italy to investigate its origin. Geometric and kinematic data indicate that the fault array consists of steeply dipping faults with both normal and reverse senses of movement. Displacement data suggest that these faults with opposed kinematics acted together , in agreement with what was previously described from analogue and numerical experiments for faults formed in response to gravitational collapses in volcanic areas. By integrating these results with considerations of the recent volcano-tectonic evolution of the Campi Flegrei caldera, we propose a model in which the studied fault array developed to accommodate a gravitational collapse triggered by an underground magma migration predating the 1538 CE historical Monte Nuovo eruption. This work is, to our knowledge, the first thorough field description of faults developed to accommodate gravitational collapses in volcanic areas. • Detailed field description and throw analysis of a volcano-tectonic fault array. • Normal and reverse faults of the array acted simultaneously. • The fault array accommodated a gravitational collapse triggered by an underground magma migration. [ABSTRACT FROM AUTHOR]

Analysis of high-resolution seismic profiles integrated with archaeological data along the coast has allowed quantifying the last ∼10 ka BP displacements in the offshore part of the Campi Flegrei resurgent caldera, one of the world's highest-risk volcanic areas. Previous onland studies revealed that, following the Neapolitan Yellow Tuff (NYT) eruption at 15 ka, post-caldera evolution was associated with rapid ground uplift and subsidence cycles. In this paper, we use the stacking pattern of Prograding Wedges (PWs) and Aggrading Fills (AF) to reconstruct relative sea-level changes and estimate the amount of vertical deformation in the Pozzuoli Bay, the submerged part of the caldera. We document five generations of prograding wedges (PW1 to PW5), associated with as many periods of relative ground stability between uplift and subsidence. Instead, deposition of aggrading fills above prograding wedges underpins the subsidence that typically follows volcanic unrest and uplift. The older wedges PW1 and PW2 are larger and likely indicate whole-caldera uplift events. In particular, the development of PW2 starting from ∼5.2 ka is related to the rapid growth of a resurgent dome in the central part of the caldera. After ∼3.7 ka, subsidence prevailed in the caldera leading to deposition of an aggrading fill (AF2). However, subsidence was interrupted by short-term uplift episodes in historical times at (100 BCE-100 CE, 600–700 CE, 1430–1538 CE) that led to the growth of comparatively minor-sized wedges PW1 to PW3, respectively. Displacement of coastal infrastructures of the Roman age (∼2 ka BP) is consistent with the vertical motion retrieved by the seismostratigraphic analysis, and further indicates the existence of two deformation signals. A short-wavelength signal confined to the Pozzuoli Bay reflects the contribution of an intra-caldera source. This signal is superposed to a long-wavelength regional subsidence increasing between Naples and Procida Island from 1.5 to 2 mm/a, respectively. The east-to-west enhancing subsidence likely reflects the transition between the uplifting Apennines and the foundered Tyrrhenian back-arc basin. • High-resolution seismic profiles analysis in the offshore Campi Flegrei caldera • Seismostratigraphic bodies document relative sea-level changes • Quantitative reconstruction of vertical ground displacements in the Holocene • Roman-age coastal remains constrain ground deformation in the last 2 ka. • We disentangle the contribution of intra-caldera dynamics and regional tectonics. [ABSTRACT FROM AUTHOR]

In the Taverna San Felice limestone active quarry (Italy) excavation has progressively exposed a magmatic dike embedded in a calcareous succession. The dike outcrops are scattered among the high vertical steps of the quarry, whereas outside the excavated area the steep mountain slope covered by a dense bush vegetation make direct inspection and geological mapping a challenging task. To map the areal extension of the dike and to define its direction and its relationship with tectonic lines over an area larger than the quarry, a magnetic survey was performed. Given the above-mentioned extremely rugged terrain, a UAV-based magnetic survey was the preferred acquisition strategy. Data were acquired by rigidly fixing the magnetometer to the UAV landing sled, using a sensor with a very high-frequency (1000 Hz) acquisition rate. The acquisition strategy and some simple processing steps resulted in a detailed drone-borne total field anomaly map. This dataset allowed for a mapping of the dike outside the quarry area and the identification of a vent fed by the dike. The 2D forward modelling of the magnetic data was constrained by a field estimation of the intensity of the total magnetization and by the depth to the dike's top, in places where it is outcropping. • The drone-borne magnetic surveys, in some cases, are the only strategy for high-resolution investigations. • To increase flight security and stability, the magnetometer was rigidly attached to the drone's landing gear. • The goal of this work was to map an igneous dike intruded in sedimentary rocks in difficult ground conditions. [ABSTRACT FROM AUTHOR]

We present a structural study on late Miocene-early Pliocene out-of-sequence thrusts affecting the southern Apennine orogenic belt. The analyzed structures are exposed in the Campania region (southern Italy). Here, thrusts bound the N-NE side of the carbonate ridges that form the regional mountain backbone. In several outcrops, the Mesozoic carbonates are superposed onto the unconformable wedge-top basin deposits of the upper Miocene Castelvetere Group, providing constraints to the age of the activity of this thrusting event. Moreover, a 4-km-long N-S oriented electrical resistivity tomography profile, carried out along the Caserta mountains, sheds light on the structure of this thrust system in an area where it is not exposed. Further information was carried out from a tunnel excavation that allowed us to study some secondary fault splays. The kinematic analysis of out-of-sequence major and minor structures hosted both in the hanging wall (Apennine Platform carbonates) and footwall (Castelvetere Group deposits and Lagonegro-Molise Basin units) indicates the occurrence of two superposed shortening directions, about E-W and N-S, respectively. We associated these compressive structures to an out-of-sequence thrusting event defined by frontal thrusts verging to the east and lateral ramp thrusts verging to the north and south. We related the out-of-sequence thrusting episode to the positive inversion of inherited normal faults located in the Paleozoic basement. These envelopments thrust upward to crosscut the allochthonous wedge, including, in the western zone of the chain, the upper Miocene wedge-top basin deposits. [ABSTRACT FROM AUTHOR]