He.R.A. Heritage at Risk Assessment: Seismic and Landslide Vulnerability Estimation of Masonry Churches for Multilayer Single-Hazard Analysis

This research was developed in response to the increasing need for coherent and integrated methodologies to assess the complex and multifaceted risks threatening cultural heritage. Three critical issues were identified at the outset. The inconsistency in terminology and the absence of standardised definitions across risk analysis frameworks, hindering both comparability between studies and the development of actionable strategies. The scarcity of methodologies capable of addressing a large number of heritage architectures, resulting in time and cost-intensive risk assessments that are tailored to specific architectural contexts and difficult to apply elsewhere. The prevailing preference for methodologies that focus on single-hazardous events often overlooks the potential for cascading or compound events, despite current risk management guidelines advocating for the integration of multi-event information in planning and preparedness strategies. To address these gaps, the research proposes a quantitative methodology for regional-scale physical vulnerability estimation, specifically targeting seismic and landslide vulnerabilities in historical churches. The adopted methodology is based on a multilayer single-hazard framework, aiming to harmonise and standardise risk analysis procedures. Physical vulnerability is expressed through an index-based approach that combines event intensity indicators with churches physical resistance indicators. While seismic and landslide phenomena are analysed independently, both are evaluated within a shared conceptual approach, which enables direct comparison and prioritisation across hazardous events. Three main phases can be identified. First, the risk context is defined by identifying the objectives, study area characteristics, and hazardous event types. A consistent and scalable data collection process is designed, including the creation of a survey form tailored to masonry churches. The survey form draws on literature-based indicators and existing vulnerability analysis methodologies to support systematic and standardised data gathering for a large building sample. Second, event-specific physical vulnerability indices are developed and validated. The seismic vulnerability index draws on a regression-based model informed by nonlinear static analyses performed on archetypes derived from a typological classification. Generalised Linear Models (GLMs) are employed to relate the probability of failure to churches main geometric attributes. The resulting seismic physical vulnerability index represents the expected tendency of vulnerability over a properly selected range of intensities. The landslide vulnerability index is adapted from an existing method and recalibrated using resistance indicators specifically selected for historical churches. Both indices range into a 0–1 scale and allow for comparability within prioritisation and disaster risk reduction frameworks. Finally, the methodology is extended to estimate scenario-based risk for earthquake-triggered landslides, combining the landslide vulnerability index with susceptibility data and uniform exposure. This scenario-based approach enables the estimation of risk without requiring information on the frequency of the triggering events. The full methodology is applied to a case study in northern Tuscany, a region characterised by high seismicity and widespread slope instability, encompassing 71 surveyed masonry churches. Results reinforce the value of an integrated yet adaptable vulnerability analysis strategy.