A Regional Seismic Risk Assessment Framework Accounting for Urban Informality and Data Limitations

Urban seismic risk assessment in the Global South is often constrained by informal construction and limited access to detailed building databases. Existing risk assessments can distinguish between building classes and estimate relative or economic losses. However, in data-limited settings, spatially explicit information on informal-settlement areas and construction-quality differences may not be available at a resolution suitable for community-level assessment. Using the canton of San José, Costa Rica, as a case study, this study aims to (1) propose a regional seismic risk assessment framework that accounts for building informality and data limitations, (2) evaluate neighborhood-level variations in seismic risk within the canton, and (3) assess the influence of informality on risk estimates across neighborhoods. The framework adapts a community-level seismic risk assessment developed by the Tokyo Metropolitan Government to the local context. Building collapse risk is estimated by combining average damage ratios and building densities for each neighborhood. Buildings located within mapped informal areas retain their observed structural typologies but are evaluated using conservative low-ductility assumptions and, where compatible, low-ductility fragility functions. Under the 475-year return-period reference scenario, the modelled mean damage ratio was 16.0%, and the mean building collapse risk was 3.6 buildings/ha. Neighborhoods containing mapped informal areas exhibited a mean collapse risk of 6.8 buildings/ha, compared with 3.3 buildings/ha in formal areas. The resulting map supports relative neighborhood ranking for seismic risk-reduction planning and risk communication in data-limited urban environments

Risk assessment · Risk management · Seismic risk · Disaster Management and Resilience · Seismic Performance and Analysis · Seismology and Earthquake Studies

• Housing networks in San José, Costa Rica

  Open Access•Harry Smith•Habitat International•2003

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