Site Characterization Using Satellite Data and Estimation of Seismic Hazard at Ground Surface

This paper presents the seismic site characterization carried out for Karnataka (state level) as well as for India (country level) using topographic slope map derived from Digital Elevation Model (DEM) data. Two DEM data, SRTM, and ASTER were used to derive the slope maps. For Karnataka (state level), the slope map was generated from ASTER DEM considering a grid size of 5 × 5 km and for India (country level), the slope map was generated from SRTM DEM considering the grid size of 10 × 10 km. Based on the slope value, every grid point was characterized into various NEHRP site classes, and spatial variation of average shear wave velocity for top 30 m (Vs30) value throughout the study areas is presented in this paper. Peak horizontal acceleration (PHA) at bedrock level was evaluated for the same grid points using deterministic as well as probabilistic methodologies. The amplification factor for every grid point was obtained from the site coefficients corresponding to NEHRP site class. The surface level peak horizontal acceleration (PHA) was then evaluated for every grid point by multiplying bedrock level PHA with the corresponding amplification factor. Spatial variation of seismic hazard at the surface for the state of Karnataka as well as for entire India is presented in this paper.