microzonation

Microzonation is a local-scale assessment of seismic hazard and ground-shaking potential that accounts for spatial variability in geological and geotechnical conditions within a region. It complements broad regional seismic hazard maps by identifying site-specific amplification and hazards that can influence structures and infrastructure. Outputs are typically maps showing zones with differing vulnerability classes, such as potential ground-motion amplification, liquefaction susceptibility, landslide risk, and soil-structure resonance potential.

The process involves data collection on geology, soils, stratigraphy, boreholes, and geophysical surveys, as well as groundwater conditions. Site characterization uses parameters like shear-wave velocity (Vs) and Vs30, along with ambient vibration measurements and laboratory tests. Modelling can employ empirical correlations or numerical site response analysis, and results are integrated in Geographic Information Systems to produce actionable maps. Classification schemes are often aligned with building code performance objectives.

Applications of microzonation include informing land-use planning, building codes, infrastructure siting, and retrofit prioritization. It supports civil protection and emergency planning by identifying areas with elevated shaking, liquefaction, or landslide risks, guiding design decisions for foundations, ground improvements, and retrofitting strategies. In practice, microzonation provides a framework for cost-effective mitigation by targeting the most vulnerable zones within urban or regional contexts.

Limitations and challenges include data density and quality, methodological differences, and inherent uncertainties in ground conditions and model assumptions. Regular updates are common as new geotechnical data become available, improving the precision and usefulness of microzonation maps.