Application of Probabilistic Seismic Hazard Assessment for Earthquake Hazard: Case Study of Karachi City, Pakistan

In this study, we analyzed a thorough examination of seismic hazard assessment for Karachi city, with the aim of ensuring the construction of safe and sustainable buildings and structures. Karachi, being the largest city and an economic hub of Pakistan, serves as the focal point for this study. The study begins by assessing the potential danger posed by an earthquake resulting from tectonic activity in the area. To accomplish this, the region, which spans approximately a radius of 200 km, is divided into eight distinct seismic zones. The study incorporates ground motion prediction equations that are compatible with the seismotectonic environment of the study area. The resulting ground motions are determined by the peak horizontal ground acceleration and the 5% damped spectral acceleration (SA). The seismic activity in the study area is primarily characterized by small to moderate earthquakes, as indicated by recorded data. Based on the historical earthquake data, it has been observed that significant earthquakes with high magnitudes have taken place within a radius of approximately 200 km from Karachi, such as the Bhuj earthquake in 2001. The primary active tectonic features in the region include the Pab Fault, Kirthat Fault, Hab Fault, Jhimpir Fault, Surjan Fault, Ornach-Nal Fault, and Rann of Kutch Faults. In order to ensure the safe and sustainable seismic design of building structures in Karachi, it is advised to adhere to the recommended seismic design parameters. These parameters include a peak ground acceleration (PGA) of 0.19g and 0.33g, with a shear wave velocity (Vs30) of 750m/sec for foundation conditions. The return period for these parameters is determined based on the nature of the structures, with a value of 475 years for one set of parameters and 2,475 years for the other.