The Frequency Domain Electromagnetic (FDEM) method is a cost-effective geophysical technique that simultaneously studies the electrical and magnetic properties of a medium, providing data as in-phase and out-of-phase components of the electromagnetic field. Although FDEM yields valuable insights, its results can be complex to interpret, and the two EM field components are normally only visually inspected to support findings from other techniques. This study aims to enhance FDEM data interpretation using an unsupervised learning technique. The proposed approach seeks to automate and expedite the interpretative phase. By applying the K-Means clustering algorithm, we divided the FDEM data into several clusters based on specific intervals of the in-phase and quadrature components, resulting in integrated maps of EM components. Combining these maps with geological and archaeological insights helped identifying areas of potential archaeological interest. This method was applied to the Torre Galli archaeological site in Calabria, Italy, known for its significance in Iron Age studies.Based on comparisons with the findings of earlier excavations and results from a magnetic survey, the proposed procedure shows promise in improving the efficiency and accuracy of the FDEM method in identifying areas of archaeological interest. This suggests that automating the interpretation process could lead to a better cost management and time optimization in geophysical and archaeological studies.

Understanding how orogenic shortening transfers from the basement to the sedimentary cover is crucial in fold-and-thrust belts. Transfer distance dictates the thrusting style. In cases of 'long-distance rooting' such as the Jura Mts.-Swiss Mollasse Basin-Alps system, the sedimentary cover's shortening leads to a thin-skinned deformation style. Conversely, 'short-distance rooting', as observed in the ramp-dominated sectors of the Southern Alps, results in thick-skinned deformation. However, the distinction of thin- vs. thick-skinned styles of thrusting may be ambiguous. 'Long-distance rooting' may cause thin-skinned deformation at the belt front and thick-skinned deformation where the basement underplates, as seen in the Alpine region. The crucial aspect in fold-and-thrust belt dynamics is whether the basement is extensively underthrust and processed in the orogen's interior ('long-distance rooting'), or if displacement directly transfers from basement thrusts to the sedimentary cover on a local scale ('short-distance rooting'). This fundamental issue is addressed here for the Umbria-Marche zone of the Apennines, which style of thrusting has been the subject of a long-lasting debate. Interpretations proposed in the last decades mostly range from pure thin-skinned to composite models of basement-involved deformation and detachment-dominated thrusting of the sedimentary cover. We aim to investigate whether the sedimentary cover is more shortened than the basement (i.e., a substantial component of ‘long-distance rooting’ of thrust displacement of the sedimentary cover) or do shortening of basement and cover balance at the scale of the foreland fold-and-thrust belt (i.e., ‘short-distance rooting’ characterizes the Umbria-Marche zone). We integrate the updated 1:50,000 scale geological map (CARG Project) of the Sibillini area (Visso and Ascoli Piceno Sheets) with a 10 m cell-size digital elevation model, the interpretation of vintage seismic lines and gravimetric data. We present a series of new balanced and restored cross-sections, including a crustal section along the trace of available seismic lines covering the entire Apennine and foothills area to the coastline, validated by gravimetric modelling, and thirteen cross-sections used to verify the geometric viability of sedimentary cover structures in the study area. The results of our work suggest coupled deformation of basement and sedimentary cover, which are characterized by similar amounts of shortening (consistent with ‘short-distance rooting’ of thrust displacement). The balanced cross-sections, integrated with a dense grid of (n. 25) additional sections perpendicular to the main structural trends, were used to construct a 3D structural model calibrated by surface geology. This allowed us to reconstruct the main fault surfaces, accounting for the along-strike variability of geological features observed from the map and offering a detailed representation of the geometrical arrangement of key horizons (base-top Calcare Massiccio Fm, top Maiolica Fm, top Scaglia Rossa Fm, top Bisciaro Fm) and their relationships with major faults. Our structural model provides new insights into the architecture, timing of the deformation, and kinematic evolution of the Umbria-Marche sector of the Apennines. This has major implications for a better understanding of deformation style, the role of structural inheritance, and post-thrusting extensional tectonics (which controls the seismotectonic setting of the study area).

A comprehensive analysis of the gravity and magnetic fields of the Phlegrean Fields volcanic area reveals a complex structural setting. High resolution techniques, including multiscale boundary analysis and field transformations, highlight the position of density and magnetization boundaries of the Phlegrean Fields. The structural elements of the two datasets appear in a general agreement, but at the same time present differences, so yielding a complex and rich picture of the collapsed Phlegrean caldera and of the surrounding areas. Inside the caldera, a good consistence among some structural elements identified from our analysis and the seismicity can be established. Some hypotheses about the geological significance of the gravity and magnetic anomalies in the frame of the Phlegrean volcanological context are finally set up.

This study investigates the tectonic and subsurface structure of the Volturno Plain, a region linking the Southern Apennines with active volcanic districts of Campania. Vintage seismic profiles were vectorized, depth-converted, and integrated with historical gravity and magnetic data. The analysis reveals a coastal half-graben structure primarily controlled by NE-trending normal faults, with NW-trending faults that downthrow the carbonate outcrops of the Southern Apennines toward the coast. These fault systems collectively drive subsidence exceeding 5 km beneath the mouth of the Volturno River. Enhanced Horizontal Derivative analysis of gravity data extends fault traces beyond the seismic coverage and helps to characterize major NE-striking fault systems, such as the Mt. Massico and Villa Literno fault zones, which are likely active and exhibit aseismic creep or low-magnitude seismicity. Gravity and magnetic anomalies highlight variations in the thickness of the sedimentary cover within fault-controlled depressions, as well as the presence of volcanic deposits in the southern plain, associated with buried volcanic edifices whose emplacement was influenced by NE- and NW-trending faults. InSAR-derived surface deformation patterns show a partial alignment with these fault systems but also reflect non-tectonic factors such as sediment compaction and anthropogenic activities. Our findings confirm the structural control of NE-trending faults on the plain's evolution and Campanian volcanism. This work fills a knowledge gap regarding the tectonic and structural setting of the carbonate basement in the northern part of the Campanian Plain, for which a map of the depth to the base of the post-Miocene sedimentary cover was not yet available. This paper also highlights the value of integrating legacy seismic and potential field data using modern techniques to unravel the interplay of tectonic and magmatic processes.

The Nazca Ridge's thickened subduction beneath the South American continental margin (10° to 15° S) is characterised by a flat-slab configuration. This peculiar geological setting strongly influences upper plate dynamics, significantly impacting stress distribution and seismicity in the South American plate. However, the effects of the Nazca Ridge subduction on the Peruvian forearc and Andean Cordillera development remain subjects of extensive debate. In this study we thoroughly investigate the general structure of the Nazca Ridge subduction zone producing an integrated two-dimensional structural-geological model of the south-Peruvian Andes. Combining surface geological data and geophysical information from existing literature, we delineated the crustal structure up to a depth of about 130 km along a ca. 1000 km-long transect, encompassing the Peruvian Forearc System and the Andean Cordillera. In order to improve the characterization of geological features and validate the model, we carried out forward modelling of the Bouguer anomaly in the region, integrating four distinct datasets. Subsequently, we formulated a two-dimensional density model to reproduce the observed gravity field, taking into consideration the petrological properties of the materials and the P-T condition in each area of the crustal section. The geometry of the structures was assessed by choosing the configuration that, honouring the geological and geophysical constraints upon which the initial model was based, also allowed maximising the fit between observed Bouguer anomaly values and the values computed during the forward modelling process. Our exhaustive approach allowed us to obtain a comprehensive model of the Nazca Ridge subduction zone, accurately defining both the deep lithosphere-asthenosphere system and shallow geological structures. This contribution will substantially enhance the ongoing debate on the tectonic evolution and geodynamics of Andean orogeny.

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SUMMARY The separation of the effects of deep-seated sources of potential fields from those of shallower ones is a frequent requirement when interpreting magnetic or gravity fields. A common procedure is estimating the regional, long wavelength, component of the field by analysing the data over an area larger than that of the local feature of interest. The local components are found by subtracting the estimated regional from the observed data. These approaches may have difficulties in their application, as the dataset over large areas may not be available and other local anomalies, in the enlarged area, may prevent a reliable estimate of the regional field. We present an alternative and simple approach to the regional-residual separation problem not requiring the analysis over large areas and aiming at estimating the local, rather than the regional, component. Our method exploits the natural enhancement of short wavelengths obtainable by computing vertical derivatives of potential fields. An equivalent layer source is computed from the vertical derivative and is used to estimate the local field. The optimal differentiation order can be determined by inspecting the obtained results. This parameter may assume even fractional values, so that the method results a very versatile tool. The application to a complex synthetic case and two real data examples demonstrates the utility of this approach. In summary, our method has some peculiar characteristics making it an interesting alternative to currently used approaches to regional-residual separation: (i) it is a local method, so it can work well even when processing datasets relative to areas of limited extension; (ii) unlike most current methods, estimating a smooth regional component, our method directly produces an estimate of the local field and (iii) it is highly versatile, as the key parameter, that is the fractional differentiation order, can be finely adjusted up to obtain an optimal local field.

•In this “Comment” article to “P. Mancinelli, V. Scisciani, S. Patruno, G. Minelli” published on Tectonophysics We want to point out that their gravity model is based on a low-resolution dataset unable to represent the gravity contribution of shallow structures and the modelling results appear compromised by methodological errors.

We propose a processing workflow to enhance the information content of aeromagnetic data. Our workflow is based on the downward continuation and subsequent L-transform of magnetic data. This workflow returns a map showing single highs, which correspond to the location of magnetic bodies, and does not need any a priori information about the source magnetization. We validated our workflow using the aeromagnetic anomalies of the Tyrrhenian Sea (Italy), by a comparison of the reprocessed aeromagnetic anomalies with high-resolution shipborne magnetic data in three selected areas. Through this comparison, we show that the proposed processing workflow of aeromagnetic data leads to more accurate interpretative results. Our results indicate that, in areas where higher resolution data are lacking, the reprocessing of aeromagnetic data according to our workflow may be as decisive as to suggest changes to their previous interpretations or, at least, useful for highlighting areas of special interest, deserving to be magnetically explored by a dedicated high-resolution shipborne survey.

Sediments infilling in intermontane basins in areas with high seismic activity can strongly affect ground-shaking phenomena at the surface. Estimates of thickness and density distribution within these basin infills are crucial for ground motion amplification analysis, especially where demographic growth in human settlements has implied increasing seismic risk. We employed a 3D gravity modeling technique (ITerative RESCaling-ITRESC) to investigate the Fucino Basin (Apennines, central Italy), a half-graben basin in which intense seismic activity has recently occurred. For the first time in this region, a 3D model of the Meso-Cenozoic carbonate basement morphology was retrieved through the inversion of gravity data. Taking advantage of the ITRESC technique, (1) we were able to (1) perform an integration of geophysical and geological data constraints and (2) determine a density contrast function through a data-driven process. Thus, we avoided assuming a priori information. Finally, we provided a model that honored the gravity anomalies field by integrating many different kinds of depth constraints. Our results confirmed evidence from previous studies concerning the overall shape of the basin; however, we also highlighted several local discrepancies, such as: (a) the position of several fault lines, (b) the position of the main depocenter, and (c) the isopach map. We also pointed out the existence of a new, unknown fault, and of new features concerning known faults. All of these elements provided useful contributions to the study of the tectono-sedimentary evolution of the basin, as well as key information for assessing the local site-response effects, in terms of seismic hazards.

Ground-shaking phenomena in intermontane basins emplaced in seismically active areas are strongly affected by sediment thickness. There, the development of human settlements, encouraged because of the flat topography in a mostly mountainous region, implies demographic growth and an increased seismic risk, as recent earthquakes in Central Italy confirmed. The knowledge of the thickness of the basin infills and of their density distribution is critical for the ground-motion amplification analysis. We apply the recently proposed ITerative RESCaling (ITRESC) method for 3D gravity modelling to the Middle Aterno Valley (Apennines, central Italy), a fault-controlled basin where a strong seismic activity recently occurred. Although the structural framework was previously investigated through 1D or 2D geophysical studies, here for the first time a full 3D model of the carbonate basement morphology is computed by the inversion of gravity data. Differently from usual gravity modelling approaches, the ITRESC technique 1) does not assume a density contrast function, which is instead determined through a data-driven process, and 2) integrates geological or geophysical constraints to define a global "gravity/depth-to-basement" resealing law, valid in all the investigated area. Our model integrates a number of depth constraints of different nature while at the same time honoring the gravity anomalies. The obtained gravity model of the basement depth shows several analogies with previous studies, although with significant, localized discrepancies. The results of this study are only partially consistent with a structural evolution of the Middle Aterno Valley through a polyphasic sequence, as previously hypothesized.

The Central and Southern Apennines are characterized by the occurrence of intense and widely spread historical and recent seismic activity, mostly located along the chain. In this paper, we present a multi-parametric data analysis in GIS environment (Geographic Information System) with the aim of identifying and constraining the geometry (strike, dip direction and dip angle) of the seismogenic faults in areas of Central-Southern Apennines characterized by outcropping/ buried and/or active/silent faults. We use an integrated analysis of geo-structural, seismological and gravimetric data, for the identification and geometrical description of faults with density contrast, both at the surface and at depth. At the surface, the gravity lineaments inferred by Multiscale Derivative Analysis (MDA) were compared with the Quaternary faults mapped in the study areas and with the earthquakes’ epicentral distribution. The characterization of faults at depth was instead performed by the combination of the Depth from Extreme Points (DEXP) gravity imaging method with hypocentral sections. We tested the effectiveness of this multi-method approach at Mt. Vettore-Mt. Bove, L’Aquila basin, Mt. Massico and San Giuliano di Puglia areas (Central and Southern Apennines). Given the effectiveness of the obtained results, this multiparametric study has been applied to other three areas of the Abruzzo-Molise region: the south-western sector of Mt. Matese, the Fucino basin and the Sulmona basin. The Matese area was hit by a seismic sequence in 2013-2014 (Mwmax= 5.1 on December 29, 2013). Our approach showed a correlation between the epicentral distribution of the 2013-2014 Matese seismic sequence (Mw=5.0) and the MDA lineaments from gravity data. The hypocentral distibution suggests that the fault rupture does not reach the surface. Therefore, the seismogenic fault responsible of 2013-2014 Matese seismic sequence is likely a buried fault. The Fucino basin was struck by a Mw=7.0 earthquake on January 13, 1915, causing 30,000 causalities within a large area surrounding the basin. At present, the area is characterized by scarce instrumental seismicity with low magnitude. Our analysis highlights a good correlation between NW-SE and NE-SW well-known faults and clear gravimetric MDA maxima bordering the plain. This area can be currently considered silent but, from historical seismological studies, it is one the highest seismic risk areas of Central Apennines. Moreover, we investigated the area of the Sulmona basin, the southwards extension of the eastern system of Central Apennines developing from Mt. Vettore, Mt. Gorzano and Mt. Gran Sasso. In historical times, the faults of the most external extensional alignment, defined as silent and considered as probable seismic gaps, activated during the 2016 Amatrice–Visso–Norcia seismic sequence. Further to the southeast, two relatively large earthquakes occurred on the eastern flank of Mt. Maiella on November 3, 1706 (Mw=6.6) and on September 26, 1933 (Mw=5.7). The Sulmona area is presently characterized by poor and low magnitude instrumental seismicity. Our multi-parametric analysis highlighted a strong correlation between MDA maxima and the Mt. Morrone normal fault bordering the western side of Mt. Maiella and the eastern side of the Sulmona basin.

Recent techniques of three-dimensional (3D) imaging of potential field anomalies are effective in estimating the source position in the subsurface by exploiting both the differentiation of the field and the stability of the method. Such a processing is fast and especially suitable for detecting isolated and compact sources, as usually are those of archaeological interest. Among these methods we employed techniques that take advantage from innovative concepts like the multiscale transformation and the scaling function, going well beyond the standard procedures usually employed for data processing with archaeological purposes. We interpreted magnetic data acquired during two geophysical surveys carried out in 2008 and 2010 at Tell Barri, in north-eastern Syria. Tell Barri is a relevant site for the history of North Mesopotamia. The earliest settlement dates back to the end of the fourth millennium bce whereas the site has been occupied - with no major breaks - until the fourteenth century ce. Based on the magnetic data interpretation, we have selected a test area as a target for an archeological excavation. The excavation found ancient structures closely matching the magnetic source revealed by the geophysical imaging. Since both the ground soil and the material of buried archaeological structures are representative of several ancient settlements in a much larger area (Upper Mesopotamia), we believe that such a geophysical approach could be successful in many archaeological sites scattered through this broad region.

In this paper, we present a new Bouguer gravity map of the Northern Tuscan offshore (central Italy), based on original gravity data acquired on the islands of the Tuscan Archipelago. Our dataset integrates 274 unpublished gravity field measurements with 126 available marine gravity data of the northern Tyrrhenian Sea. The Bouguer anomaly map shows a westward and southward increase of the regional gravity field associated with the uplift of the Moho boundary from central Apennines towards the Tyrrhenian Sea. At a local scale, several Bouguer anomalies are well associated with the igneous plutons of the Elba, Montecristo and Capraia islands, as a result of a deep density contrast between the granitoid intrusive rocks and the embedding metamorphic basement. The presented Bouguer anomaly map represents a useful tool for future studies of the complex geological and geodynamical setting of the Tuscan Archipelago and of the buried and deep igneous structures.

We report the results of a multidisciplinary investigation performed across the normal Quaternary faults that ruptured the surface during the August 24 (M-w 6.0) and October 30 (M-w 6.5), 2016 strong earthquakes in the Mt. Vettore-Mt. Bove areas, central Italy. Our aim is to test the effectiveness of the contribution of a multi-scale gravimetric analysis in characterizing seismogenic faults' geometry at hypocentral depths on well-known outcropping faulty systems with known earthquake distribution. We adopted a multi-scale geophysical/geological approach consisting in the comparison of gravity lineaments inferred by Multiscale Derivative Analysis with the Quaternary structural setting mapped in the study area, the primary coseismic surface ruptures of the 2016-2017 sequence and the earthquakes' epicentral distribution. Moreover, we performed a combined interpretation of 2D hypocentral sections of the 2016-2017 seismic sequences with images resulting from the Depth from Extreme Points method. to infer the faults geometry at depth. Based on our results, the investigated NW-SE Mt. Vettore-Mt. Bove fault system is dipping 60 degrees-70 degrees westward. We also detected the splays of this primary fault and its blind antithetic NW-SE structure, dipping northeastward. In the Norcia basin we highlight two main faults bordering the basin with a dip of about 45 degrees. The one edging the eastern side dips westward. whereas the fault edging the western side dips eastward. Thanks to our analysis we could identify and characterize the geometry of the Norcia and Vettore master faults, as well as other blind/buried and/or silent faults that are related to the 2016 seismogenic structure. Our results show the effectiveness of this approach in potentially high-hazard areas that are structurally poorly known.

We analyze a wide gravity low in the Campania Active Volcanic Area and interpret it by a large and deep source distribution of partially molten, low-density material from about 8 to 30 km depth. Given the complex spatial-temporal distribution of explosive volcanism in the area, we model the gravity data consistently with several volcanological and petrological constraints. We propose two possible models: one accounts for the coexistence, within the lower/intermediate crust, of large amounts of melts and cumulates besides country rocks. It implies a layered distribution of densities and, thus, a variation with depth of percentages of silicate liquids, cumulates and country rocks. The other reflects a fractal density distribution, based on the scaling exponent estimated from the gravity data. According to this model, the gravity low would be related to a distribution of melt pockets within solid rocks. Both density distributions account for the available volcanological and seismic constraints and can be considered as end-members of possible models compatible with gravity data. Such results agree with the general views about the roots of large areas of ignimbritic volcanism worldwide. Given the prolonged history of magmatism in the Campania area since Pliocene times, we interpret the detected low-density body as a developing batholith.

We present the results of a multidisciplinary and multiscale study at Mt. Massico, Southern Italy. Mt. Massico is a carbonate horst located along the Campanian-Latial margin of the Tyrrhenian basin, bordered by two main NE-SW systems of faults, and by NW-SE and N-S trending faults. Our analysis deals with the modelling of the main NE-SW faults. These faults were capable during Plio-Pleistocene and are still active today, even though with scarce and low-energy seismicity (M-w maximum = 4.8). We inferred the pattern of the fault planes through a combined interpretation of 2-D hypocentral sections, a multiscale analysis of gravity field and geochemical data. This allowed us to characterize the geometry of these faults and infer their large depth extent. This region shows very striking gravimetric signatures, well-known Quaternary faults, moderate seismicity and a localized geothermal fluid rise. Thus, this analysis represents a valid case study for testing the effectiveness of a multidisciplinary approach, and employing it in areas with buried and/or silent faults of potential high hazard, such as in the Apennine chain.