Gaetano Memmolo

Investigating slope deformation in densely vegetated or remote areas is a major challenge for slope stability assessment. This study introduces and validates an integrated UAV-borne low-frequency Ground Penetrating Radar (UAV-GPR) and LiDAR methodology to characterize an unstable slope in Melizzano, Southern Italy. Radar data were acquired along an east–west transect at ~1 m above ground level, while high-resolution LiDAR were used to generate a detailed Digital Terrain Model for topographic correction and geomorphological analysis. The processed radargram images subsurface features down to ~15 m, revealing a laterally continuous high-amplitude reflector at ~10 m, interpreted as a key main sliding surface. Chaotic reflections above this interface indicate heterogeneous deposits associated with gravitational deformation, while more homogeneous reflections below correspond to stable geological units. The geometry of the reflector suggests a compound landslide mechanism. Borehole data validate the geophysical interpretation, showing depth discrepancies lower than 2 m. The integration of UAV-GPR and LiDAR enables a reliable correlation between surface morphology and subsurface structures. This non-invasive, spatially continuous approach provides an effective framework for subsurface characterization and for improving the interpretation of landslide geometry and internal structure in challenging environments. This study demonstrates the capability of low-frequency UAV-borne GPR to detect deep-seated sliding surfaces (>10 m) in vegetated environments when integrated with high-resolution LiDAR topography.

This study presents an integrated geophysical–geomatic approach for the investigation of archaeological sites, combining low-frequency Ground-Penetrating Radar (GPR) and close-range photogrammetry at the Archaeological Park of Abellinum (southern Italy). Unlike conventional applications using high-frequency antennas, the low-frequency GPR system employed in this study enabled deep subsurface imaging, allowing reconstruction of buried stratigraphic and architectural features to depths of several metres. This enhanced penetration capacity facilitated a more comprehensive understanding of the investigated environments, by complementing rather than replacing high-frequency surveys and expanding the interpretable volume in complex urban and peri-urban contexts. GPR reflection data were integrated with high-resolution photogrammetric surface models, enabling direct comparison between visible structures and subsurface geometries. The combined dataset provided precise correlations between surface features and subsurface anomalies, demonstrating the potential of this integrated methodology for detailed archaeological interpretation. Overall, this approach offers a scalable, non-invasive framework applicable to other complex archaeological landscapes, supporting both research objectives and long-term heritage management. By systematically combining low-frequency GPR with high-resolution photogrammetry, the study introduces a methodological contribution that extends interpretative depth well beyond the limits of conventional surveys.

Ground Penetrating Radar (GPR) is a powerful tool for imaging shallow stratigraphic and structural features. This study shows that it is particularly effective also in detecting near-surface evidence of active faulting. In the Southern Apennines (Italy), one of the most seismically active regions of the Mediterranean area, the shallow expression of active faults is often poorly constrained due to limited or ambiguous surface evidence. Low-frequency GPR profiles were acquired in the Calore River Valley (Campania Region), an area historically affected by large earthquakes and characterized by debated seismogenic sources. The surveys employed multiple antenna frequencies (30, 60, and 80 MHz) and both horizontal and vertical acquisition geometries, enabling penetration depths ranging from ~5 m to ~50 m. The acquired GPR profiles, integrated with high-precision georeferencing, were able to reveal the presence of shallow steeply dipping active normal faults striking E–W to ENE–WSW, here named the Postiglione Fault System. Therefore, this study highlights the methodological potential of low-frequency GPR for investigating active faults in carbonate substratum and fine-to-coarse-grained sedimentary units and thus contributing to refining the seismotectonic framework and improving seismic hazard assessment of seismically active areas such as the Southern Apennines.