Impact of Topography on Seismic Amplification During the 2005 Kashmir Earthquake

This study assesses topographic amplification of seismic response during the 2005 Kashmir Earthquake in northern Pakistan. Topography scatters seismic waves, which causes variation in seismic response on the surface of the earth. During the Kashmir earthquake, topography induced amplification was suspected to have had major influence on the damage of infrastructure. We did a 3-dimensional simulation of the event using SPECFEM3D software. We first analyzed the impact of data resolution (mesh and Digital Elevation Model) on the derived seismic response. ASTER GDEM elevation data was used to build a 3D finite element mesh, and the parameters (latitude, longitude, depth, moment tensor) of the Kashmir earthquake were used in simulating the event. Our results show amplification of seismic response on ridges and de-amplification in valleys. It was also found that slopes facing away from the source receive an amplified seismic response when compared to slopes facing towards the source. The PGD would regularly fall within the range 0.23-5.8 meters. The topographic amplification causes local changes in the range of -2.50 to +3.50 meters; causing the PGD to fall in the range of 0.36-7.85 meters.