Advancing Paleoseismology with Integrated Hyperspectral and Multi-Sensor Approaches: Enhanced Interpretation of Trenches and Active Fault Scarps in Spain and Italy

Paleoseismology extends earthquake records by documenting geological evidence of past surface-rupturing events, providing constraints for seismic source characterization, and improving the understanding of fault behavior. The reliability of paleoseismological interpretations depends on observational data and analytical methods. Conventional trenching and bedrock-scarp studies face uncertainties, as surface processes can obscure subtle deformation, and chronological correlations between units are often poorly constrained. Ground-based remote and direct sensing techniques now enable centimeter-scale multi-sensor datasets that significantly enhance observation and documentation of paleoseismic evidence.

This study builds on established methodologies to explore the integration of ground-based hyperspectral imaging, LiDAR, photogrammetry, and direct field measurements for improved detection of coseismic deformation, paleoearthquake identification, and 2D–3D reconstructions of fault displacement (for slip-rate estimation). The approach is applied to two active tectonic settings in the western Mediterranean: the Alhama de Murcia Fault within the Eastern Betics (SE Spain), with dominant transpression, and the Southern Fucino Fault System, Central Apennines (Italy), with dominant extension. At first, paleoseismological trenches were studied in alluvial sediments at the Saltador site. Second, an exhumed limestone fault scarp was analyzed at the San Sebastiano site.

At the Saltador site, 13 wall trenches excavated parallel and perpendicular to the fault, together with a natural outcrop, were logged using conventional paleoseismology and combined with remote sensing to reconstruct 2D–3D fault deformation and identify displaced alluvial-channel piercing points for slip-rate estimation. At San Sebastiano, LiDAR and photogrammetric data were combined with direct field measurements (spectroradiometry and Schmidt hammer rebound values) to characterize fault-surface roughness, mineralogical variability, and rock mass properties, to detect progressive scarp exhumation, building on existing ³⁶Cl cosmogenic constraints. Hyperspectral imagery was acquired using an AISA Fenix 1K (400–2500 nm) at the Saltador and SPECIM FX10/FX17 (400–1700 nm) at San Sebastiano. Radiometric correction, co-registration with point clouds, and illumination modeling were performed using the hylite package. Subsequent processing included dimensionality reduction (MNF, PCA) and mineral-sensitive band ratios for lithological and structural discrimination.

The integration of hyperspectral data enhanced paleoseismological interpretations in both study areas by reducing uncertainties in coseismic deformation and surface rupture detection. At the Saltador site, previously unrecognized secondary faults and surface ruptures within alluvial sediments were revealed. Spectral band ratios improved the discrimination of sedimentary facies and erosional contacts, strengthening the identification of piercing points and deformation patterns. At least three paleoearthquake events over the past ~34 ka were confirmed, enabling refined 3D reconstructions of offset deposits and an estimated horizontal slip rate of ~0.2 mm/yr for the studied fault branch.

At San Sebastiano, visible to near-infrared hyperspectral data captured spatial variability in alteration minerals (e.g., hematite–goethite and, possibly, hydrated clay minerals), delineating vertical spectral zones that correspond to ³⁶Cl-dated exhumation clusters, suggesting a link between mineralogical variability and progressive scarp exhumation. Combined with roughness and rock-strength measurements, these results could help to refine scarp exhumation rates, surface-rupturing earthquake sequences, and spatial variability in fault-rock exposure.

Overall, hyperspectral and multi-sensor ground-based techniques can enhance the reliability, reproducibility, and robustness of paleoseismological analyses in complex tectonic settings.