The heterogeneous medium structure along the propagation path adds significant complexities to the far‐field P‐wave spectra. High‐frequency seismic waves radiated by explosions are strongly affected by the site conditions (i.e., subsurface geology and topography), as well as by the velocity and attenuation structure along the propagation path. Therefore, removing the propagation and site effects is particularly important for explosion monitoring. To achieve this goal, a nonparametric generalized inversion method (Andrews, 1986; Boatwright et al., 1991) was implemented to simultaneously estimate the source spectra and the medium transfer functions for the six nuclear explosions conducted by North Korea. For the recovered source spectra, the estimated value of the exponent relating the corner frequency to the low‐frequency asymptote is found to be approximately . The scaling of the explosion source spectra estimated for this dataset is shown to be consistent with the explosion source model prediction (Mueller and Murphy, 1971; Denny and Johnson, 1991). The successful application of the method to the North Korean nuclear test data shows promising results for future use in the explosion monitoring studies.