An updated probabilistic seismic hazard assessment (PSHA) for Pakistan

Abstract

In this study, an updated probabilistic seismic hazard assessment (PSHA) of Pakistan region is performed using the procedures developed for the US National Seismic Hazard Maps and the Earthquake Model of the Middle East (EMME14). It is based on the combination of conventional area sources model and the spatially smoothed gridded seismicity model with crustal faults. An updated earthquake catalogue is compiled using several international and national databases. The background seismicity of the study area is modeled using both the area source zones and the spatially smoothed gridded seismicity approach. A total of 110 crustal fault sources are modeled using their geological slip rates obtained from the database developed by the Global Earthquake Model (GEM). The Makran Subduction Zone (MSZ) is also modeled using a combination of inclined area source zone and the spatially smoothed seismicity approach. Several Ground Motion Prediction Equations (GMPEs) developed by the PEER Next Generation Attenuation (NGA) initiative are employed to estimate the hazard at bedrock level. The logic tree procedure is used to deal with the epistemic uncertainties associated with the source models and the GMPEs. The updated hazard maps for the Peak Ground Acceleration (PGA) and Spectral Accelerations (SA) at natural periods of 0.2 s, 1 s and 2 s are developed for the 10% and 2% probability of exceedance in 50 years (DBE and MCE levels, respectively). The hazard curves and Uniform Hazard Spectra (UHS) for several major cities of Pakistan are also presented. The results provide an updated understanding of the seismic hazard in Pakistan. The presented hazard maps, curves and spectra can be used for the structural design of new buildings as well as the performance assessment of existing buildings. They also provide an improved basis for the policy formulation and planning for effective disaster risk reduction in the region.