Impact of uncertainty in remote sensing DEMs on topographic amplification of seismic response and Vs30

Impact of topography on spatial variation of seismic response is well-observed synthetically, experimentally, and visually during seismic events. Numerical and experimental investigations for predicting topographic impact on seismic response are often 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 evaluating the impact of topographic features on amplification or de-amplification of seismic response. Seismic events located in rough terrain, like the 2005 Kashmir earthquake in northern Pakistan, exhibit intensified seismic response and associated devastation at hill ridges and on inclined slopes. Satellite remote sensing-derived digital elevation models (DEMs) are frequently and effectively used to compute topographic attributes and seismic parameters to evaluate topographic seismic response. However, the influence of DEM random errors on computed topographic attributes and seismic response is often overlooked. This study uses the Shuttle Radar Topography Mission (SRTM) DEM (90 m) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) GDEM (30 m) to quantify uncertainties in the computed topographic attributes and seismic parameters and ultimately the impact of these uncertainties on topographic seismic response. Accuracy assessment of the DEMs shows root mean square error (RMSE) of 13.78 m in the ASTER DEM and 23.71 m in the SRTM DEM. The influence of DEM errors on derived topographic attributes quantified through Monte Carlo simulations shows higher uncertainty in slope and aspect computed from ASTER DEM than from SRTM DEM. The influence of uncertainty in the SRTM and ASTER DEMs shows significant impact on the computed seismic parameters of slope, relative height, and Vs30 and ultimately derived topographic seismic response.