Probabilistic seismic hazard analysis for Kakrapar atomic power station, Gujarat, India

Seismic ground motion caused by earthquakes mainly affects the constructions and structures around its area of influence. In this context, the probabilistic seismic hazard analysis (PSHA) is a scientific step towards the safety analysis of any major construction such as nuclear power plant. Thus, the present study focused to estimate seismic hazard level at different probabilities for Kakrapar nuclear power plant located in the Western India. The hazard curves for the study area are developed following the procedure of PSHA suggested by Cornell–McGuire. Three source zones, Narmada-Tapti zone (NTZ), Rann of Kuchchh (ROK), and west passive margin (WPM), are classified on the basis of seismicity and tectonic setting of the study area. The estimated maximum magnitude (m _max) for NTZ, ROK, and WPM are 6.9 ± 0.57, 6.5 ± 0.64, and 6.1 ± 0.64, respectively. Logic tree approach has been used for the development of hazard curves to account the epistemic uncertainties associated with the analysis. For maximum credible earthquake MCE, i.e., the probability of exceedance of 2 % in 50 years (return period of ~2,500 years)], the peak spectral acceleration (i.e., PSA at 0.2 s) expected around 5 km of the Kakrapar nuclear power plant (site) is 0.23 g from all source zones; however, at exact site location, it is 0.18 g. The PSA values due to NTZ, ROK, and WPM based on MCE are 0.22, 0.065, and 0.052 g, respectively. In case of design-based earthquake (DBE, i.e., 50 % probability in 50 years (return period of ~110 years)), the calculated maximum spectral acceleration (SA) from all source zones is about 0.045 g. The PSA distribution for the DBE from the NTZ has reached a maximum value of 0.042 g; however, PSA for ROK and WPM is considerably low with a maximum value of 0.022 and 0.021 g, respectively. Considering the MCE and DBE, the estimated PSA at 0.2 s has a highest value of ~0.23 g from all source zones. Spectral accelerations (SAs) correspond to different periods are presented, and SA plots for NTZ zone can be considered as response spectra for the KAPS site. Deaggregation of PSHA in the present study is also discussed. PGA values reported in seismic zonation map and global seismic hazard analysis program around the present study area range from 0.05 to 0.2 g which is slightly lower than the peak acceleration obtained in this study. The results of this study would facilitate in the performance of the site-specific seismic probabilistic safety analysis.