Microzonation for Urban Planning

Microzonation is identification of areas having different earthquake hazard potentials and will primarily serve for urban planning and land use management. The two principal factors controlling earthquake loss are site response and structural features. The seismic microzonation maps would indicate the distribution of site response with respect to ground shaking intensity, liquefaction and landslide susceptibility; thus providing an input for urban planning and earthquake mitigation priorities at an urban scale. It is also possible to estimate building damage and causalities based on microzonation maps used as an input to earthquake risk scenarios. These estimates may be very approximate based on the accuracy of the input data and methods of analysis. However, they can also be more realistic when more comprehensive data and more sophisticated analysis methods are implemented. The first stage in an earthquake risk scenario is the estimation of the earthquake hazard on the ground surface based on seismic microzonation maps for detailed assessment of earthquake response on the ground surface. The seismic microzonation maps, in other words earthquake hazard maps, are prepared using estimated earthquake characteristics on the ground surface based on local site conditions and input earthquake characteristics. The estimation of damage and causalities for buildings, lifelines and transportation networks is the second stage and is considered as earthquake damage scenarios. In order to assess the effects of earthquakes in urban areas, it would be necessary to compile historical earthquakes, geological, geotechnical and seismological data, to evaluate the probabilistic and deterministic earthquake hazard, to determine the variation of earthquake characteristics with respect to local site conditions, and microzonation and damage maps that need to be drafted utilizing GIS software packages. Within the contents of this chapter, the first stage of earthquake risk scenarios, microzonation - probabilistic earthquake hazard scenario will be presented based on some case studies.