The Metropolitan Area of Lisbon (MAL) has the highest population and building density in Portugal, and is exposed to medium to high magnitude earthquakes due to its geographical location. Currently, the MAL housing stock is constituted by approximately 35% of masonry residential buildings with a large variability of materials and construction techniques, as a result of many centuries of history. Most of these buildings were built before the introduction of the first design code for building safety against earthquakes (RSSCS) in 1958 RSCCS. 1958. National standard: Code for building safety against earthquakes (Original title: Regulamento de Segurança das Construções contra os Sismos – RSCCS). [Google Scholar] and therefore were only designed to support gravity loads. Given the presence of these buildings in areas of significant seismicity, a comprehensive research is needed to assess the seismic risk and define mitigation policies for this population of unreinforced masonry buildings. The main purpose of this work is thus to geometrically characterize these typologies, through an exhaustive survey of dozens of masonry buildings collected from original drawings and identify the most important aspects that can influence their seismic behavior. After a compressive historical background, the information collected is statistically analyzed and expressed through probability distributions that can be used for the development of numerical models and derive seismic vulnerability functions, fundamental to conduct seismic risk analyses.

Traditional unreinforced masonry structures are extremely vulnerable to seismic events, featuring large losses in many countries worldwide. This study focuses on the seismic assessment of a traditional masonry structures located in Faial Island—Azores (Portugal), which was hit by an earthquake of M _w = 6.2 on 9 July 1998. A set of analyses was conducted through a probabilistic performance‐based seismic approach, employing a stochastic finite‐fault ground‐motion simulation method to derive region‐specific records and nonlinear numerical models to compute the capacity of the building. Subsequently, analytical fragility curves were derived considering different seismic scenarios. The results show a significant probability of the structural typology to reach moderate to extensive damage in the case of the specific earthquake, as observed in reality. The study holds significant importance in regions with limited recorded seismic activity, as they offer potential benefits for seismic risk management and mitigation strategies.