Integrated electrical resistivity tomography and geological characterization of the upper San José de Aloburo landslide, Pimampiro, Imbabura

Abstract

Landslides are a major hazard in mountainous regions of the Ecuadorian Andes. This study examines the upper and accessible sector of the complex San José de Aloburo landslide, Imbabura Province, by integrating electrical resistivity tomography (ERT) with surface geological observations, three stratigraphic columns, and local grain-size information. Four Wenner-array ERT profiles were acquired with a low-cost, non-commercial system and imaged to approximately 35–40 m depth. The inverted sections contain broad low-resistivity domains (approximately 4–45 Ω m) and higher-resistivity domains reaching approximately 297 Ω m. Because electrical resistivity is non-unique with respect to lithology, moisture, porosity, weathering, and pore-fluid properties, these domains are interpreted jointly with the geological observations rather than as direct indicators of saturation, cohesion, or a mechanically verified slip surface. Geoelectrical boundaries in Profiles 1, 2, and 4 are spatially consistent with potential instability-related boundaries in the upper landslide sector, but this interpretation remains indirect and lacks borehole or geotechnical confirmation at depth. The stratigraphic columns document alternating ash and pumice/lapilli units, whereas the quantitative sieve analysis available for sample ANG-TOP-B-01 provides only local sedimentological support and is not extrapolated to the entire landslide. The integrated dataset demonstrates the value of combining ERT and field geology in a volcaniclastic Andean setting while also defining the limitations imposed by survey coverage, inversion non-uniqueness, seasonal hydrological variability, and incomplete archival documentation of the custom instrumentation.