Luigi Capozzoli

Playa lakes are considered promising landing sites on Mars because of their strong astrobiological potential. Therefore, sediments and buried structures in terrestrial playa lakes have become the focus of numerous analogue studies. The inclusion of ground penetrating radar (GPR) in the payloads of Martian missions has opened new avenues for subsurface investigations enabling comparisons between buried structures on Earth and Mars. This study presents nine first‐of‐their‐kind radargrams, imaging to depths of ca. 15 m, from the Makgadikgadi Pans (Botswana), a playa lake analogue for Mars basins. The GPR surveys targeted buried faults, relict fan deltas, and layered mounds. Despite challenges posed by shallow brines and the water table, GPR successfully imaged internal geometries within the mound, supporting possible genetic models linked to groundwater upwelling. The radargrams also confirmed brine upwelling along buried faults and deltaic geometries previously identified only through satellite imagery. These findings provide important terrestrial analogs for interpreting the Mars subsurface and refining our understanding of its hydrological evolution.

Historical urban centres of high cultural and monumental relevance are commonly characterized by complex and highly heterogeneous subsurface settings, resulting from the superposition of natural geological deposits, archaeological layers, and centuries of anthropogenic modifications. In such contexts, limited or fragmented subsurface knowledge may hinder archaeological interpretation and constrain multidisciplinary analyses aimed at urban reconstruction and heritage preservation.This contribution is framed within the Italian PRIN 2022 project NEW AGE (New Integrated Approach for Seismic Protection and Enhancement of Heritage Buildings on Historic Earthen Deposits) and presents results from non-invasive geophysical investigations conducted at two emblematic monumental sites: the Roman Amphitheatre (Arena) of Verona and the Santa Sofia monumental complex in Benevento, both characterized by prolonged and stratified occupation histories, leading to highly heterogeneous near-surface conditions. The investigations benefited from advanced geophysical instrumentation made available through the IRPAC and ITINERIS research infrastructure (funded through regional and national programs, respectively), supporting enhanced data acquisition capabilities within the project framework.We propose a multi-scale, multi-method geophysical approach designed to improve the characterization of shallow subsurface conditions in densely built and historically layered urban environments. The investigation strategy combines ground-penetrating radar (GPR), electrical resistivity tomography (ERT), and seismic methods, selected to explore complementary physical properties and depth ranges while accommodating site-specific logistical and conservation constraints.GPR surveys provided high-resolution imaging of shallow subsurface heterogeneities and anthropogenic features, supporting the identification of archaeological remains and spatial variations within near-surface layers. ERT investigations complemented these results by resolving broader geological structures and deeper resistivity contrasts, allowing reconstruction of subsurface variability at different spatial scales. Seismic measurements contributed additional constraints on subsurface layering and mechanical properties.The combined interpretation of the different datasets acquired, supported by archaeological and geotechnical information where available, provides a robust and physically consistent reconstruction of the shallow subsurface in complex, historically layered monumental settings. The multi-method geophysical framework enables the identification of stratigraphic heterogeneities, anthropogenic layers, and buried structures, reducing subsurface uncertainty in complex heritage contexts and supporting subsequent geological, archaeological, and engineering analyses.

Transportation networks rely heavily on bridges whose safe operation depends on maintaining structural soundness. Natural phenomena, such as landslides and human-induced incidents, pose significant threats to bridges, with consequences ranging from compromised safety to complete failure and service interruption. Multiple variables determine the extent of structural deterioration, including the nature of hazardous events, material composition, and existing maintenance conditions. A comprehensive evaluation of landslide-related threats necessitates examining a variety of factors, including the geophysical properties of the subsoil and an in-depth knowledge of the bridge key structural elements, such as its foundations, piers, and abutments, as well as their current state of conservation.Supported by the FABRE consortium, the EMILI project - ElectroMagnetic techniques for Investigating Landslide and structural damages due to their Impacts on bridges - aims to establish uniform protocols and operational frameworks for electromagnetic investigation techniques in bridge-landslide hazard evaluation. By targeting Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR), EMILI advances the standardization, reliability, and field implementation of electromagnetic approaches.Initial findings from EMILI are discussed here, encompassing two primary contributions. The first concerns a comprehensive literature analysis examining both capabilities and constraints of ERT and GPR in field applications involving bridges, landslides, and their interactions. The second deals with preliminary results from simplified numerical models exploring the detection potential of ERT and GPR when applied via conventional and unconventional measurement configurations. Specifically, surface and borehole data from simulated scenarios involving diverse lithologies, foundations, and water content are considered and processed to establish the potential and limitations of ERT and GPR in estimating the shape and depth of the foundation piles.Preliminary synthetic results are promising and demonstrate the capability of ERT and GPR to identify foundation structures in simplified geological contexts.

In some cases, soils exhibit a layered structure clearly identified even at the depth scales investigated by Ground Penetrating Radar (GPR) surveys. However, not many methods and computational tools are available that systematically address imaging in layered soils. Imlaymed (Imaging in Layered Media) is a Python graphical user interface (GUI) freeware software specifically designed to tackle this problem. The code assumes either a two layered soil or a cavity embedded within a homogeneous soil. In the latter case, the cavity is locally interpreted as a three-layered medium. The interfaces between adjacent layers are assumed smooth—which is geologically reasonable—although not necessarily planar. However, the non-flatness of the layers precludes the possibility of obtaining an analytical solution. Consequently, Imlaymed addresses the focusing and time–depth conversion issues as an imaging problem rather than an inverse scattering problem. The method explicitly accounts for the presence of two distinct propagation velocities within the soil, which results in geometric distortions, including dilation and compression effects on both the targets and the distances among them. Imlaymed aims to mitigate these distortions. The current release represents an initial version of the software, to be progressively updated and extended. Future developments are expected to introduce additional capabilities—e.g. time-reverse migration—and to enhance the existing features, e.g. through the incorporation of AI techniques and the optional use of parallel computing. In particular, Imlaymed will aid to generation of slices directly in the spatial domain instead of the common slices built up in time domain.The methodology underlying the code is based on our previous results [1-6]. The implementation of this code has improved both the computational efficiency and the ease of use of the algorithms. Notwithstanding, the user of Imlaymed is supposed to have some non-too-basic background experience in GPR prospecting.Imlaymed is distributed under AUL/ANCL License (Academic Use License/Academic Non-Commercial License).AcknowledgementsThis work has been implemented within the activities of the Research Project “Georadar e avanzamento delle investigazioni: un’applicazione economica alla sicurezza stradale”, financed by University of Calabria.ReferencesPersico, G. Morelli, Combined Migrations and Time-Depth Conversions in GPR Prospecting: Application to Reinforced Concrete, Remote Sens. 2020, Volume 12, Issue 17, 2778, open access, DOI 10.3390/rs12172778.Persico et al. “A posteriori insertion of information for focusing and time–depth conversion of ground-penetrating radar data”, Geophysical Prospecting, open access, https://doi.org/10.1111/1365-2478.13369, 2023.Persico et al., ­GPR mapping of cavity in complex scenarios with a combined time-depth conversion, Sensors, MDPI, Sensors 2024, 24(10), 3238; https://doi.org/10.3390/s24103238, 2024.Persico et al., An innovative time-depth conversion for the management of buried scenarios with strong discontinuities, Journal of Applied Geophysics vol. 227, 105435, DOI 10.1016/j.jappgeo.2024.105435, 2024.Yang et al., Accounting for the Different Propagation Velocities for the Focusing and Time–Depth Conversion in a Layered Medium, Applied Sciences 14(24):11812, 2024.Persico et al., Retrieving the propagation velocity of the electromagnetic waves in a two-layered medium through the diffraction curves, Near Surface Geophysics, 1–13. https://doi.org/10.1002/nsg.70028, 2025.

Ultrasonic pulse velocity (UPV) is a widely used technique for diagnosis and structural safety assessment of existing buildings. The main difficulties in UPV tests on-site are due to one-sided accessibility of materials and degraded/irregular surfaces. Pulse-echo ultrasonic tomography (PE-UT) can overcome the problem. Though it has been widely applied for detecting inhomogeneities within concrete, few works use the instrument to assess UPV. The present paper aims to fill the gap by comparing PE-UT results with those of through-transmission ultrasonic tests (TT-UT) commonly used for UPV characterization. TT-UT measurements were performed with cylindrical and exponential transducers. The latter are used on irregular surfaces or when coupling gel is forbidden. Few data are in the literature comparing exponential and cylindrical transducers’ results. This is a further element of novelty of the paper. PE-UT and TT-UT results were compared considering the effect of material compositeness, water, transmission mode, and transducer type. It was found that PE-UT allows for reliable and rapid one-sided measurements on concrete and stone in different conditions. The differences between PE-UT and TT-UT results were between 1 and 3%. Exponential transducers gave reliable results on fine-grained stone in direct transmission, with differences lower than 4% with cylindrical transducer results.

The Italian NEW AGE project (PRIN 2022 “New Integrated Approach for Seismic Protection and Enhancement of Heritage Buildings on Historic Earthen Deposits”) seeks to advance seismic risk mitigation strategies for all cities with significant monumental heritage and all historic centres.The project adopts a holistic approach, treating the urban environment as an integrated soil-building system, to assess and address the mutual interactions between subsurface conditions and overlying cultural heritage structures. This approach is crucial for the effective preservation of heritage sites in seismic-prone areas.Seismic investigations, integrated with electromagnetic (GPR) and electrical resistivity tomographies (ERTs), provide non-invasive methods suitable for investigating subsurface conditions and foundation structures beneath urban environments. GPR is particularly effective for characterizing the shallower layers of subsoil and for detecting possible buried archaeological features. Similarly, ERT is a robust and cost-effective method for delineating the geometry of geological structures in urban areas, at greater depths.The project employs a multiscale, multiresolution geophysical strategy to comprehensively study the geological subsurface, soil-foundation systems, and heritage structures. By integrating these methods, the PRIN NEW AGE project aims to provide a robust framework for seismic risk mitigation and the sustainable preservation of cultural heritage in urban areas. The proposed strategy was tested to characterize the subsurface of the Arena di Verona from an archaeological and geological point of view, through the combined and integrated use of Seismic, GPR and ERT. In this presentation, only the results obtained with GPR and ERT will be presented while the seismic analyses will be presented by Gallipoli et al. in the work “Rapid and non-invasive structural characterization of the Roman Arena in Verona, Italy, through geophysical prospecting”. GPR acquisitions were performed with a monochannel system coupled to antennae operating at different frequencies, and a multichannel GPR stepped-frequency system equipped with an external GNSS system. GPR data collected by the first GPR system, operating at frequencies of 200 and 400 MHz, allowed the identification of the Arena foundation system, while the multichannel system, leveraging the unmatched resolution offered, enabled the identification of interesting anomalies within the amphitheatre and surrounding areas, belonging to different historical phases.ERTs were carried inside the Arena and in Piazza Bra. In Piazza Bra, two ERTs were conducted with a 5-meter electrode spacing, covering a total length of 235 meters, to investigate depths of up to several tens of meters for geological purposes while, in the Cavea, two ERTs were conducted in two different arcades, along with a roll-along ERT survey in the longitudinal tunnel beneath the Cavea for improving the resolution and supporting the archaeological research.The information obtained with GPR and ERTs, supported and validated by archaeological data and geotechnical drilling have provided highly valuable insights from both the engineering and the archaeological perspectives.Geophysical activities are realized also exploiting instrumentations and facilities provided by the Research Infrastructures of IRPAC (financed by PO FESR Basilicata 2014-2020 – DGR n. 402 del 28.06.2019 / CUP: G29J19001190003) and ITINERIS (financed by European Union – Next Generation EU, PNRR, M4C2 inv.3.1, CUP B53C2200215000).

Bridges and viaducts are critical elements of transportation infrastructure, and ensuring their structural integrity is vital for safety and functionality. These structures are susceptible to damage from natural events, like landslides, or from human-made accidents, which can lead to severe consequences such as structural collapses, traffic disruptions, and safety risks. The severity of these impacts depends on factors such as the type of landslide and the design and condition of the infrastructure. Evaluating landslide risks requires a thorough assessment of various factors, including the geophysical properties of the soil and the condition of key structural elements of the bridge or viaduct, such as foundations, piers, and abutments. Remote and in-situ electromagnetic technologies are increasingly employed for this purpose, but there is currently no standardized protocol for their effective application. Existing risk assessments are often inconsistent, varying from case to case and heavily relying on the expertise of the operators. Moreover, the effectiveness of each electromagnetic technology is influenced by the specific scenario, the devices used, and the user's skill in interpreting the data. The EMILI project aims to address these challenges by developing standardized guidelines, best practices, and protocols for the use of electromagnetic technologies in assessing landslide risks for bridges and viaducts. The project has two primary goals: (1) to conduct a systematic review of the performance of available remote and in-situ electromagnetic technologies, and (2) to advance the use of electrical and electro-magnetic geophysical methodologies for investigating bridge foundations and structural assessments. The EMILI project is funded by the FABRE consortium, a technical and scientific Italian alliance for monitoring, promoting and assessing the safety of bridges and viaducts in Italy

Corrosion of reinforced concrete structures represents one of the main causes of degradation for civil structures and infrastructure, making the development of innovative strategies for monitoring their health strongly recommended. In this context, non-invasive geophysical methodologies have been demonstrated to be effective, but the information provided is often qualitative and not fully usable for engineering purposes [1-2].A laboratory test was conducted at the Hydrogeosite CNR-IMAA facility to explore the potential of resistivity methods and electromagnetic techniques, aiming to uncover new relationships between signal variations and degradation phenomena.Using an integrated approach, including Ground Penetration Radar (GPR), ultrasonic tests, and electrical techniques within the framework of the Icarus Project (PRIN Project 2022), a set of reinforced concrete samples was designed and subjected to accelerated corrosion tests in a saline solution. These samples are continuously monitored to identify corrosion phenomena in the rebar and degradation of the concrete.The final goal of the test is to experimentally link bond-slip performance through the combined use of non-destructive testing (NDT) methodologies, supported by mechanical pull-out tests. This study highlights the pressing need to develop innovative strategies for monitoring the health of reinforced concrete structures, given the significant risks posed by corrosion. The integration of geophysical and non-destructive testing (NDT) methodologies forms the core of this research, aiming to bridge the gap between qualitative data and actionable engineering insights.The methodologies developed in this study offer practical applications for assessing corrosion levels in reinforced concrete structures. The integration of geophysical and conventional NDT data provides an efficient, non-invasive approach for routine monitoring, which is particularly valuable for monitoring engineering structures.Research activities are realized also exploiting instrumentations and facilities provided by the Research Infrastructures of IRPAC (Infrastruttura Tecnologica e di Ricerca per lo studio del passato umano, la Conservazione e Gestione del Patrimonio Culturale) and ITINERIS , Italian Integrated Environmental Research Infrastructures System). ReferencesFornasari, G.; Capozzoli, L.; Rizzo, E. Combined GPR and Self-Potential Techniques for Monitoring Steel Rebar Corrosion in Reinforced Concrete Structures: A Laboratory Study. Remote Sens. 2023, 15, 2206. https://doi.org/10.3390/rs15082206Capozzoli, L.; Fornasari, G.; Giampaolo, V.; De Martino, G.; Rizzo, E. Multi-Sensors Geophysical Monitoring for Reinforced Concrete Engineering Structures: A Laboratory Test. Sensors 2021, 21, 5565

The effective use of Ground Penetrating Radar (GPR) in urban environment benefits of the ability to manage data referred to a layered scenario. The GPR imaging in layered media can be improved either making use of focusing algorithms [1-2] accounting in a rigorous way for the layered structure of the soil or, more simply and less demandingly from the point of view of the available computing resources, making use of a joined migration and of a combined time-depth conversion of the data [3-4]. These recently introduced possibilities allow to deal with layered media as homogeneous ones. The inhomogeneity of the investigated medium is, indeed, accounted for through a sort of sticking of different results and with some suitable deformation of the resulting image. Advantages of the combined time-depth conversion but also its intrinsic limits will be discussed. For example, it is helpful for the correct imaging of cavities [5] allowing, in a simple and straightforward way, the mitigation of the well-known compression effect that the cavities suffer in a classical GPR imaging. This claim is supported by both numerical results obtained from data simulated with the gprMax software [6] and by experimental results obtained in real test scenarios.Key words: Layered media, joined migration, combined time-depth conversionReferences[1] R. Pierri, G. Leone, F. Soldovieri, R. Persico, "Electromagnetic inversion for subsurface applications under the distorted Born approximation" Nuovo Cimento, vol. 24C, N. 2, pp 245-261, March-April 2001. [2] I. Catapano, L. Crocco, R. Persico, M. Pieraccini, F. Soldovieri, “Linear and Nonlinear Microwave Tomography Approaches for Subsurface Prospecting: Validation on Real Data”, IEEE Trans. on Antennas and Wireless Propagation Letters, vol. 5, pp. 49-53, 2006. [3] R. Persico, G. Morelli, G. Esposito, I. Catapano, L. Capozzoli, G. De Martino, D. Yang, An innovative time-depth conversion for the management of buried scenarios with strong discontinuities, Journal of Applied Geophysics vol. 227, 105435, DOI 10.1016/j.jappgeo.2024.105435, 2024. [4] D. Yang, L. Capozzoli, I. Catapano, G. De Martino, G. Esposito, G. Morelli and R. Persico, Accounting for the Different Propagation Velocities for the Focusing and Time–Depth Conversion in a Layered Medium, Applied Sciences 14(24):11812, 2024. [5] R. Persico, S. D'Amico, L. Matera, E. Colica, C. De, Giorgio, A. Alescio, C. Sammut and P. Galea, GPR Investigations at St John's Co‐Cathedral in Valletta. Near Surface Geophysics, vol. 17 n. 3, pp. 213-229. doi:10.1002/nsg.12046, 2019. [6] C. Warren, A. Giannopoulos, I Giannakis, gprMax: Open source software to simulate electromagnetic wave propagation for Ground Penetrating Radar, Computer Physics Communications, 209, 163-170, 2016 10.1016/j.cpc.2016.08.020.