Line profiles of Si IV 1394 Å (blue) and 1403 Å (purple) at loop positions prior to the bifurcated eruption. In the upper panels, the Doppler velocity and integrated ratio, R, were derived from moment analysis. The ratio r(Δλ) is plotted with error bars. The vertical dashed lines indicate the line center of two Si IV resonance lines, while the dashed horizontal lines are for r(Δλ) = 2. The lower panels show the observed Si IV 1394 Å line (histogram) and fit line profiles (red, blue, and purple) at each position. The velocities, v₁, v₂, and v₃, were derived from Gaussian fitting of each component. The dashed green lines indicate the combined Gaussian fitting. The χ² values in each panel have been divided by the number of degrees of freedom.