Digital surface models derived from historical aerial imagery in highly anthropized areas applied to active fault studies (eastern Betics, Spain)

Abstract

Landform recognition and surface analysis are critical in geomorphological and morphotectonic studies. In particular, the detailed study of the surface expression of active faults is essential for their characterization as seismic sources in fault-based seismic hazard models. However, increasing anthropogenic action has profoundly altered the natural landscape, degrading or erasing tectonic landforms, and limiting the accurate characterization of active faults in many regions worldwide. A paradigmatic example is the southeastern Iberian Peninsula, where extensive agricultural development over last decades has completely transformed the natural landscape. To address this limitation, we produced three historical Digital Surface Models (DSMs) using historical aerial imagery across two active faults in the Betic Cordillera: the Palomares and Llano del Águila faults. Two DSMs were generated for the Palomares Fault (one from the American B-series Flight, 1956–1957, and one from the Interministerial Flight, 1973–1986), and one DSM was generated for the Llano del Águila Fault from the Interministerial Flight, all with a spatial resolution of 2 × 2 m. We introduce Surface Roughness as a new diagnostic metric to assess quality and to identify model artifacts, while DEM of Difference analyses were used to quantify elevation changes and assess the consistency of the reconstructed surfaces. Rather than focusing solely on absolute geolocation accuracy, our approach emphasizes evaluating the reliability of the historical surface reconstruction. This methodology highlights the potential of historical aerial imagery to enhance active fault characterization and near-fault morphotectonic analyses in landscapes heavily modified by anthropogenic activity.