Engineering-geological and geophysical surveys for archaeological risk assessment in view of mitigation measures at Aegina Kolonna, Greece

Abstract

The archaeological site of Aegina Kolonna, a prominent cultural heritage landmark in Greece, is increasingly threatened by geological hazards, including coastal erosion, seismic activity, and slope instabilities. The progressive retreat of the calcarenite sea cliffs has already led to the loss of unexcavated historical remains, posing a severe risk to the site’s longterm preservation. Within the framework of the TRIQUETRA (Toolbox for assessing and mitigating Climate Change risks and natural hazards threatening cultural heritage) European Project, an interdisciplinary approach that integrates engineeringgeological, geophysical, and archaeological investigations has been adopted to assess site vulnerability and implement targeted mitigation strategies. A comprehensive geological survey identified the primary factors driving cliff instability, while ambient seismic noise measurements helped characterize the subsurface conditions and assess local seismic amplification effects. The structural stability of key archaeological elements, such as the last standing column of the Apollo Temple, was also evaluated, revealing resonance frequencies in the range 5-8 Hz, which may influence its seismic vulnerability. In addition to hazard assessment, the TRIQUETRA project focuses on heritage conservation of this site, particularly of the northeastern prehistoric settlement. Past restoration efforts relied on cement-based mortars, which have deteriorated over time, leading to structural instability. To address this, new interventions include detailed documentation, the replacement of degraded materials with lime-based mortars, partial backfilling to stabilize exposed foundations, and the implementation of long-term monitoring strategies. These measures aim to enhance structural resilience while adhering to international heritage conservation guidelines. This study underscores the necessity of a holistic approach to cultural heritage management, demonstrating how scientific research and restoration practices can be integrated to mitigate geological and environmental risks and ensure the sustainable preservation of archaeological sites.