GIS APPROACH GEOSPATIAL APPLICATION FOR SEISMIC MICROZONATION STUDY
In the paper GIS approach for seismic microzonation map compilation is presented. Approaches of Indian and Russian seismic microzonation practice are considered and compilated in express GIS technique. A first level seismic microzonation map of Chennai city has been produced with a GIS platform using the themes, viz, Peak Ground Acceleration (PGA), Shear wave velocity at 3 m, Geology, Ground water fluctuation and bed rock depth. The peak ground acceleration for these seismic sources were estimated based on the attenuation relationship and the maximum PGA for Chennai is 0.176 g and for Vladikavkaz 0.2 g (for 5% exceedance probability). The seismic microzonation analysis involved grid datasets (the discrete datasets from different themes were converted to grids) to compute the final seismic hazard grid through integration and weightage analysis of the source themes. The Chennai city has been classified into three broad zones, viz, High, Moderate and Low Seismic Hazard. Vladikavkaz city microzonation map was presented in MSK-64 scale. In both approaches shear wave velocities was one of the basic instrumental data. Using as initial data of the scenario synthesized records, taking into account the characteristics of faults, takes into account the transformation of the original accelerograms stipulated by soil properties of the territory.