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The present study attempts to assess the seismic hazard parameters (a, b and M c) and their spatial variation in western Himalaya, central Himalaya and Indo-Gangetic plain areas (19–38 ∘ N and 72–91 ∘ E ). The earthquake catalogue is prepared from different available sources, within a region of 500 km surrounding the study area, in moment magnitude scale. The maximum likelihood estimation method is used for spatial variation of seismicity parameters. The study area is disaggregated into small grids of 0.5 ∘ × 0.5 ∘ , and the spatial variation of seismicity parameters is analysed for the complete catalogue period. A significant variation in seismicity parameters is observed while moving from west to east along the Himalayan belt within the study area. Due to significant variations in seismicity parameters, instead of assigning a lumped value of seismic hazard parameter to the entire region, distributed seismic hazard parameter is assigned by dividing the entire area into five zones, of similar level of seismicity. The estimated seismicity parameter a for these zones varies from 4.28 to 6.18, and for b, it varies from 0.80 to 1.03. Using these Gutenberg–Richter parameters a and b, the present study estimated the return periods and probability of different magnitudes of earthquake for each zone. [ABSTRACT FROM AUTHOR]