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Modelling the impact of topography on seismic amplification at regional scale

Anggraeni, Dita (2010) Modelling the impact of topography on seismic amplification at regional scale.

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Abstract:Earthquake triggered ground shaking depends not only on the characteristics of earthquake source parameters and medium of seismic waves propagation, but also on the site effects. These site effects are often not included in regional ground shaking models, especially local topography, where hill ridges amplify and hill bases de-amplify seismic waves. Development in satellite and remote sensing technologies have made digital elevation models (DEMs) freely available at high resolution, and with global cover. DEMs derived from ASTER (30m) and SRTM (90m) can therefore be utilized to model the impact of topography on seismic response. In this study, seismic waves propagation generated by 2005 Kashmir earthquake were simulated using a 3D spectral finite element code called SPECFEM3D. The ground shaking simulations and peak ground acceleration maps were generated initially assuming the homogenous ground surface and later by including the topography. Topography derived from ASTER and SRTM DEMs were simulated separately to predict the impact of DEM resolution on computed ground shaking simulations and maps. The result from model simulations shows that seismic waves are dispersed at the topographic discontinuities, leading to intensification of seismic response at some hill ridges. Comparing the simulations with and without topography also verified that the ground shaking was intensified at the hill ridges and steep slopes and has a variation of 70% greater than in the valleys, as consequences of incorporated different resolution of medium DEMs resolution. Therefore, this study demonstrated the significant impact of topography on variation of ground shaking and how seismic response modeling can benefit from the readily available global DEMs in modelling more realistic earthquake. Keywords: ground shaking amplification, spectral-element method, ground motion, surface topography, Kashmir earthquake, Digital Elevation Model accuracy, Digital Elevation resolution
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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