Superposition is based on delays from the blast log provided by the blaster and delays resulted from the spatial finiteness of the blast. The latter are calculated from the burden (the distance of the shot to the free face) and spacing (the distance between shots) of the blast. Frequency-domain superposition is adopted as the default method. The method reduces the spectrum distortion caused by time-domain method because of the discrete time-domain sampling that usually requires the shifting of delays to the nearest sampling points.
1 Muller, R. A. and J. R. Murphy (1971). Seismic characteristics of underground nuclear detonations part I. Seismic spectrum scaling, Bull. Seism. Soc. Am. 61, 1675-1692.
2 Anandakrishnan, S., S. R. Taylor and B. W. Stump (1997). Quantification and characterization of regional seismic signals from cast blasting in mines: a linear elastic model, Geophys. J. Int. 131, 45-60.