Multi-technique approaches to diagnose unstable ground: Origin of the structural damages in Ciudad Victoria (Loja, Ecuador) case-study

Abstract

The Andes region exhibits high susceptibility to landslides, leading to significant infrastructure, road, and agricultural damage. This study focuses on Ciudad Victoria, a housing program located in a geologically unstable area of Loja, Ecuador. Loja has experienced frequent landslides in recent decades, with Ciudad Victoria initially affected in 2011 and 2015, intensifying during the rainy season in early 2021. However, a comprehensive understanding of this case is currently lacking. Here, we evaluate terrain instability and structural damages through a comprehensive multi-technical approach. In this study, we integrate advanced techniques such as Differential Interferometric Synthetic Aperture Radar (DInSAR), Uncrewed Aerial Vehicles (UAV)-supported field surveys, geomorphological assessments, Electrical Resistivity Tomography (ERT), and a semi-quantitative evaluation of house damages using a Geographic Information System (GIS). The combined analysis of DInSAR, field surveys, and geomorphological observations reveals that soil instability in Ciudad Victoria is primarily influenced by slow-moving translation-type landslides occurring in the SW-NE and S-N directions. These landslides exhibit an average active displacement of 1–4 cm/yr, which increases during the rainy months, reaching velocities of up to 13 cm per month. ERT, supported by the aforementioned observations, indicates a displaced soil volume of approximately 5 Hm3, with dimensions of roughly 700 m (length), 400 m (width), and 20 m (thickness). A semi-quantitative evaluation reveals that four houses have irreversible structural damages, while 172 houses exhibit severe damage and 553 houses display moderate damages such as cracks and fractures, which also impact water and sewage pipelines. Additionally, we demonstrate how these building damages can be utilized to determine terrain movement, serving as (1) ground-truth information for validating DInSAR data, and (2) facilitating detailed movement characterization. This study exemplifies the effectiveness of coordination among a multidisciplinary team that utilizes diverse techniques and perspectives, ultimately leading to a more precise diagnosis of unstable areas.