Improvement of the resilience of historic areas to climate change and other risks. The role of rock substrate and masonry stone quality on earthquake damage: the contribution to seismic risk in historic centres

The seismic sequence that occurred in Central Italy during the 2016-2017 period resulted in significant destruction, leading to the loss of invaluable artistic and architectural heritage in numerous historic centres across four Italian regions. Camerino – Marche region, heavily affected during this event, represents a case study to explore the geological and material factors that influenced earthquake damage. The present study investigates the interaction between the quality of masonry stone, the variability of the underlying rock substrate, and the subsequent amplification in case of seismic events, providing scientific foundations for risk mitigation and cultural heritage preservation. A novel, non-destructive approach using the Equotip hardness tester was developed to evaluate weathering deterioration in sandstone monuments. Applied to a sandstone column in Camerino, the analysis revealed a 15% reduction in hardness from depth to surface and a 25% overall reduction compared to fresh sandstone from the original quarry site. This method, coupled with granulometric, porosimetric, and mineralogical analyses, identified key weathering processes, including freeze-thaw cycles and pyrite oxidation which led to pores expansion and carbonation of the outer surfaces. The methodology was then extended to masonry blocks across Camerino’s historic centre, combining sedimentological and mechanical analyses to link building materials to ancient quarry sites. This work provided a framework for selecting compatible materials for restoration, balancing structural integrity and aesthetic coherence. The study also investigated the role of subsurface litho-stratigraphy in seismic amplification. By integrating geological, geotechnical, and geophysical data, a detailed engineering-geological model was developed. Two buildings with similar construction characteristics but contrasting earthquake damage were analysed. Differences in subsurface stratigraphy—alternating stiff and soft layers beneath one building and a weathered homogeneous profile beneath the other—resulted in varying amplification factors which can justify the different damage levels. Equotip data on outcrops and seismic velocities highlighted reduced mechanical performance in weathered units, correlating with higher damage levels. This research underscores the importance of integrating material characterisation, geological modelling, and provenance studies to enhance seismic risk assessment and conservation strategies. The proposed methodologies provide transferable tools for preserving cultural heritage, identifying the possible contributions to seismic risk and improving the resilience of historic centres in seismically active regions.