A theoretically relation is presented between the seismological Fourier amplitude spectrum and the elastic input energy spectrum. The presented relationship provides an important basis for better understanding of the relationship between input energy spectra and other seismological variables, such as magnitude, focal distance, path, and site effects. In this study, the contribution of these sources of variability to the uncertainty in input energy is examined using stochastic analysis, Monte Carlo simulation, to compare the effect of these earthquake ground motion parameters. Analytical results show that the influence of earthquake magnitude, focal distance, and soil condition are important for the shape and amplitude of input energy spectra.
