Seismic design response spectrum for the Islamabad Capital Territory (ICT)
Keywords:
Probabilistic seismic hazard analysis; Short and 1 second spectral acceleration; Design spectraAbstract
Pakistan is a seismically active country and its capital Islamabad is located close to an active thrust fault (Main Boundary Thrust). After the 2005 Kashmir earthquake, earthquake engineers worked on the important aspects of ground excitation that effect the structures. Seismic hazard assessment approaches are introduced by the researchers together with earthquake engineers to mitigate the ground motion. The probabilistic approach has recently been used by different researchers for the estimation of strong ground motion parameters for the closely spaced grid of 1 km. Usually, peak ground acceleration (PGA) at a bedrock level is calculated in this approach, which is used in earthquake resistant design structures or seismic safety assessments. However, PGA alone does not apply to design against the seismic loads, and modern building codes emphasis on the use of spectral acceleration values (short period and 1 second).
In this context, the capital city Islamabad is re-studied for seismic hazard analysis and new design parameters required by IBC 2012 codes to define the seismic loading are derived. These parameters are correlated with the study of Bhatti et al. (2011) which indicate that not only F series sectors in Islamabad are prone to seismic hazard, but the whole of the capital is hazardous. Based on the results of response spectra for a short period and 1 sec period, the areas occupied in the basin part of the city are more prone to hazard and hence are not suitable to construct multistorey heavy structures.
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