Predicting topographic aggravation of seismic ground shaking
at regional scale
Muhammad Shafique 1,2, Mark van der Meijde 1, Norman Kerle 1, Freek van der Meer 1 , M. Asif Khan 2
1International Institute of Geo-Information Science and Earth Observation (ITC), the Netherlands
2National Center of Excellence in Geology, University of Peshawar, Peshawar, Pakistan
The undisputable impact of topographic features on the uneven distribution of seismic ground shaking and associated devastation, is well observed and documented, but not applied at a regional scale. Seismic events located in rugged terrain, such as Kashmir earthquake (2005) in western Himalaya, exhibit amplified response on the inclined slopes and ridge crests, while de-amplified response at the hill toe. These observations are supplemented by numerical, analytical and the experimental investigations. Current efforts on predicting topographic impact on seismic response are confined to synthetic terrain or isolated hills. The available regional models like USGS Shake Map ignore the topographic effects on seismic response, limiting model applicability at local scale. Parametric studies analyzing impact of specific terrain feature and seismic characteristics on seismic ground shaking resulted in numerical models, predicting topographic aggravation of seismic response. This project aims to apply DEM derived topographic attributes and the seismic characteristics in numerical models to predict topographic aggravation of seismic response at regional scale.
SRTM and ASTER DEMs are utilized to derive the required topographic attributes and, also to investigate the impact of DEM resolution and data source on computed attributes. The uncertainty in the computed topographic attributes, due to DEM inherent random errors, is quantified through Monte Carlo Simulations. The impact of slope angle, aspect, curvature, height, wavelength and damping on amplification and de-amplification of seismic response is analyzed in homogenous lithological and geotechnical scenario. The spatial variation of wavelength and frequency content of seismic waves is estimated empirically from instrumental ground shaking records. The remote sensing DEMs are found to be sensitive to steep slopes in terrain representation. The amplified seismic response in observed to be sensitive to the slope inclination among the analyzed parameters. The direction of incident seismic waves has significant impact on the occurrence and spatial distribution of seismic induced landslides. |
