Impact of topographic parameters on seismic amplification applying Geospatial tools

The impact of topography on the uneven distribution of seismic response is well observed synthetically, experimentally and visually during seismic events. Numerical and experimental investigations for predicting topographic effects on seismic shaking are limited to isolated and/or synthetic hills and ridges. Furthermore, most of these studies only focus on one of the many terrain parameters necessary for analyzing the impact of topographic features on amplification or de-amplification of seismic response. Seismic events located in rough terrain, like the Kashmir earthquake (2005) in the western Himalaya, exhibit intensified ground shaking and associated devastation at hill ridges and on inclined slopes. Regional seismic ground shaking maps developed through USGS-ShakeMap ignore this topographic impact. DEM derived topographic attributes and seismic event characteristics can be integrated, to predict the topographic seismic amplification.

Satellite sensor's acquired SRTM (90 m) and ASTER (30 m) DEMs are employed to compute terrain attributes, and also to investigate the impact of DEM random errors and resolution on the topographic attributes, and topographic seismic response. Data disparity of SRTM and ASTER DEMs, and derived topographic attributes, imply the sensitivity of satellite remote sensing DEMs, to rugged terrain and steep slopes. Impact of DEM random errors on derived topographic attributes is quantified through Monte Carlo Simulation that shows higher consistency of SRTM DEM to derived topographic attributes. Impact of slope angle, relative height, wavelength and damping on amplification and de-amplification of seismic response is analyzed, in homogeneous lithological and geotechnical environment. Seismic response is predicted to be sensitive to the slope geometry, among the analysed parameters. DEM resolution and random errors have meager impact on the predicted topographic seismic response.