Abstract:
Seismic hazard evaluation is a fundamental component of earthquake risk mitigation and management. Pakistan lies on a seismically active and earthquake-prone region of the world. The country and its surrounding region possess a complex seismo-tectonic environment where Arabian, Indian and Eurasian tectonic plates are in a constant state of slow collision with different rates of movement. The complex plate interaction has resulted in the formation of several active faults in country. These faults pose a very high level of seismic hazard which may result in high seismic risk to many densely populated cities of the country. In the current study, the probabilistic seismic hazard analysis of Pakistan is carried out using the area source mode developed from an updated earthquake model. A new catalog of historical and instrumentally recorded earthquakes has been compiled using multiple databases. Shallow and deep seismic area sources are delineated on the basis of updated earthquake catalogue and depth of hypocentres. Several ground motion models are appropriately selected and were employed to estimate the hazard at bedrock level. The logic tree procedure is incorporated to counter the epistemic uncertainties in the seismic source model. Seismic hazard maps for peak ground acceleration (PGA) and spectral accelerations (SA) are developed for 0.5%, 2%, 5%, 10% and 69% probability of exceedance in 50 years. The hazard curves and uniform hazard spectra (UHS) for major cities of Pakistan are also developed. The deaggregation analysis for major cities is also carried out to determine the contribution of all the potential seismic sources to the total hazard. The ultimate results give a better understanding of the seismic risk at major metropolitan cities in Pakistan. The developed hazard maps, curves and spectra have many practical applications which include structural design and evaluation of currently constructed and existing structures and the improved basis for disaster risk reduction policies. Keywords: Pakistan, Seismic hazard maps, Peak ground acceleration, Spectral acceleration, Uniform hazard spectra.
