Seismic zonation of Nepal using probabilistic seismic hazard analysis

Probabilistic seismic hazard of Nepal (PSHA) followed by seismic zonation is carried out for enclosed polygon within 26.5°N–30.5°N latitude and 80°E–89°E longitude. Mixed type of ground motion prediction equations (GMPEs) derived for active shallow crustal and subduction interference with areal and linear sources was used by logic tree approach. The seismic hazard map showed higher concentration of PGA in the Himalayan region of the far western, central, and eastern parts where the rate of seismicity is very high as compared to that in other parts of Nepal and lower in the northern and southern parts of Nepal with estimated PGA to be 0.12–0.52g, 0.22g–0.55g, and 0.25–0.59g for hard, medium, and soft soil respectively. Since large spatial variation of hazard levels was observed for various cities, so seismic zonation map was constructed by dividing whole Nepal into five seismic zones. The spectral curve for soft, medium, and hard soil was also plotted and the maximum spectral acceleration value thus obtained was 1.24, 1.21, and 1.07 for the natural time period between 0.15 and 0.25 s, respectively. The results were also compared with the revised Nepal National building code NBC 105: 2020. © 2021, Saudi Society for Geosciences.