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The Global Earthquake Model (GEM) Foundation joined an international team of earthquake engineers and researchers that documented contrasting levels of building damage during a 15–26 September reconnaissance mission in western Colombia, following the magnitude 7.4 earthquake on 10 August. Preliminary field updates from the Earthquake Engineering Field Investigation Team (EEFIT), led by Arup structural engineer Sebastian Kaminski, describe collapsed reinforced-concrete buildings, damaged masonry structures and landslide-affected areas, while reporting no collapses among improved, cemented bahareque bamboo housing inspected near Armenia.

The mission, composed of specialists in seismic engineering, building vulnerability, geotechnical hazards and disaster-resilient construction, was joined by co-leaders Alejandra Albuerne of IE University (Madrid) and Helen Crowley, Secretary General of the GEM Foundation, along with researchers and engineers from Imperial College London, Build Change, Universidad de los Andes in Venezuela and the National University of Singapore. The investigation also received remote sensing and geospatial support from the University of Houston.

EEFIT's preliminary field updates documented several structural problems. In Quibdó, investigators observed poor-quality masonry, corroded reinforcement and failures involving buildings on unstable ground. In Armenia, they recorded damage from pounding between adjacent buildings, unrestrained masonry walls and inadequately detailed staircases. In Pereira, several three- to six-storey residential buildings experienced partial or complete collapse, alongside failures at beam-column connections and roofs.

Other locations showed different outcomes. In Cali, buildings designed under more recent seismic regulations generally performed better than some older reinforced-concrete structures. Improved bahareque houses inspected near Armenia had no reported collapses, although investigators found moisture-related deterioration and termite damage in some materials. Landslides and ground cracking also affected roads and other infrastructure.

The team combined rapid damage surveys, detailed building inspections and geotechnical investigations. Using the app QField, investigators recorded geolocated observations of building characteristics, damage and photographs, supported by satellite-based assessments. As part of its support to the ARISTOTLE partnership, GEM had also produced rapid impact estimates shortly after the earthquake, providing a basis for subsequent comparisons with damage observed in the field.

As a mission co-leader, Helen observed striking differences in building performance. She recalled entering one of three buildings still standing after 13 neighbouring buildings collapsed, and visiting a residential complex where two of five buildings had collapsed while the others appeared to have limited structural damage. In Cali, she saw damaged social housing where residents, previously relocated from flood-prone areas, were afraid to return.

GEM plans to compare field observations with its risk estimates, particularly in Cali, where a more detailed model was developed through the USAID-funded TREQ project. Working with local researchers and authorities, it will examine potential overestimation of fatalities, differences between observed and predicted damage patterns, and the representation of building types in its models. The analyses will contribute to EEFIT's reconnaissance report and future improvements to earthquake risk assessment.

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