Probabilistic Seismic Hazard Analysis Based Zoning Map of Pakistan

Pakistan has been a victim of earthquakes from time to time. A reliable quantification of seismic hazard is important to reduce the life and economic losses in future. This paper presents the details of probabilistic seismic hazard analysis for Pakistan which was conducted to determine ground motion parameters required for the design of structures. A seismicity model comprising areal sources and fault systems was employed for modelling earthquake activity. The country was divided into several areal zones considering the spatial and temporal distribution of earthquakes which was documented with the help of a catalogue. A number of faults and fault systems were also included in the analysis. Two types of Poissonian models were used to model earthquake recurrence for the areal and lines sources separately. Existing attenuation relationships in the literature were employed to relate the seismicity with the distance. The analysis was carried out using a commercial computer programme and hazard curves were determined for different return periods and spectral periods for response spectral acceleration. A seismic zonation map for Pakistan was developed for the quantification of seismic loading. Uniform hazard spectra were calculated and were compared with the design spectra in the existing code which indicated differences between the two types of spectra.