On the role of planning policies in the seismic vulnerability of historic urban areas: evidence from Santiago, Chile

This research presents an interdisciplinary study on the impact of planning policies on the seismic vulnerability of historic areas, encompassing architecture, urban planning, and engineering aspects. It examines the spatial and temporal dynamics of urbanization and population growth, which alter cities' seismic exposure and vulnerability over time. Urban and engineering research methods are used to assess the seismic vulnerability variability in Yungay Quarter, a historic district west of downtown Santiago, Chile, with buildings constructed between 1839 and 2022. The study begins with a thorough review of Chilean urban planning policies and building regulations, combined with a detailed survey of the construction features in the historical neighborhood to classify building types. Next, the macro-seismic method is applied to a representative sample of 484 buildings to calculate vulnerability indices for unreinforced masonry and reinforced concrete structures, which are then used to estimate damage distributions. Seismic fragility curves for each building class are derived based on peak ground acceleration. These fragility curves are incorporated into risk assessments for potential ruptures along the San Ramon, Santiago splay and a deep intra-slab splay fault. The resulting risk scenarios can guide future urban planning policies and processes affecting this historical urban center. The innovations introduced by this work include a summary of how changes and updates to planning policies have influenced construction practices in the Yungay Quarter from 1839 to 2022 and the translation of these urban changes into variations in building fragility functions, enabling a comprehensive assessment of the potential impacts on these buildings from various potential.