Dynamical spectra of icosΩ (top panel) and ecosϖ (bottom panel) for orbits with initial inclinations i₀ = 2°. The five most significant frequencies for each orbit are plotted against their initial semi-major axes. The frequencies with the largest amplitudes are labelled by red open circles while the second to the fifth are denoted by black open inverted triangles, squares, triangles, and diamonds, respectively. The blue dashed lines indicate the absolute values of the fundamental frequencies identified to be corresponding to forced frequencies. From top to bottom, they represent |s₆|, |s₃|, |s₄|, 2g₇ − s₅, g₄, g₃ + s₃ − s₄, g₂, and g₅ respectively. We note that s₃ and s₄, (g₃+s₃−s₄) and g₄ are so close to each other that they are hardly distinguishable in the figure. Moreover, for a better vision, we just plot one-third of the data.