Mass distributions of selected elements as a function of radial velocity for the spherically symmetric explosion at the labeled years from the explosion. Upper left panel: initial conditions from Ono et al. (2020). Only the dominant fractions are considered. M_i is the total ejecta mass of element i, ΔM_i is the mass of the ith element in the velocity range between v and v +δv. The size of the velocity bins δv is 100 km s⁻¹. The black dashed vertical line shows the approximate reverse shock position in each panel.