Site amplification using 1D seismic site response analysis in Islamabad: An application of building code of Pakistan 2021

Abstract. This study investigates the site amplification factors in Islamabad, Pakistan, as per seismic regulations of a newly enacted Building Code of Pakistan (BCP, 2021). Using a series of 1D non-linear site response analyses, the study evaluates these factors for the Islamabad region. Nineteen representative profiles were selected from a dataset of 125 site profiles, classified according to the Code. The representative profiles were subjected to a combination of thirteen ground motions that are compatible with site class B of the BCP, 2021, and 1D nonlinear seismic site response analyses were performed. Calculated response spectra and amplification factors are compared with design estimates provided by the code spectra. The study finds that while the Code-based design spectrum aligns with the current study’s findings for periods greater than 0.5 seconds, it underpredicts the response for shorter periods for both SC and SD site classes. These findings highlight the need for a more refined approach in the seismic provisions for Islamabad to ensure accurate seismic hazard assessments and improved earthquake safety.