The seismic vulnerability of building aggregates in Italy’s historic centres is a complex and critical issue, necessitating a multidisciplinary and multi-scale approach. Although the seismic behaviour of such structures has been widely studied, certain methodological gaps remain, particularly regarding the so-called "aggregate effect" and the combined consideration of in-plane and out-of-plane failure modes.

This study focuses on the historic residential core of Lavello (PZ), a small medieval town in the northern part of the Basilicata region, classified as seismic zone 2. The CARTIS form, which is a building inventory tool developed within the framework of the Italian DPC-ReLUIS project, was employed to collect detailed data on the building stock.

An initial analysis of the urban evolution within the historic sector was conducted to identify recurring aggregation patterns and their developmental origins. This was followed by a detailed survey of the key features of the residential masonry buildings, including masonry type, floor system, number of storeys, construction period, and state of preservation. A comprehensive building inventory is an essential foundation for both seismic risk mitigation planning and the development of vulnerability models through numerical methods.

Later on, this preliminary investigation supported the selection and definition of a representative prototype aggregate, characterized in terms of both geometry and mechanical properties. Therefore, the prototype was modelled using the 3Muri macro-element software. Nonlinear static and dynamic analyses were then performed to derive seismic fragility curves, covering all limit states and both principal directions, and capturing the global damage mechanisms. Finally, these analyses ultimately aimed to generate vulnerability curves for structural units within aggregates at the municipal scale.