Underground cavities and their aggravation effects on the local seismic response: a parametric analysis

Abstract

Underground cavities are widely distributed in urban areas and pose a significant risk to buildings and infrastructures. Beyond structural instability issues, cavities can significantly affect seismic wave propagation, modifying the amplitude, frequency content, and duration of ground motion. This study presents an integrated approach to investigate the dynamic response of underground cavities, combining two-dimensional numerical modelling of seismic wave propagation and in situ ambient vibration measurements. The numerical analyses, performed under linear-elastic conditions, aim to explore the interaction between seismic input and underground cavities. In a similar way, ambient vibration measurements carried out at the Ghar il-Latnija cave (Malta) were analysed using Operational and Numerical Modal Analysis techniques. The results highlight local amplification effects and marked spatial variability in the dynamic response, providing a preliminary framework for assessing the seismic response of underground cavities.