Figure 6: (a) Example for the spectrograms (sensor 5, transversal component) over the 5-hour time window (10:00–15:00 UTC). Please compare with the PSD estimate at sensor 5 shown in Figure 4. (b) PSD estimates of sensors on both sides along the bridge deck plotted together for each component on a log-linear scale. Black dashed lines: frequencies of the vibration modes considered for deriving the modal shapes of the bridge. The modes are annotated by their roman number, as given in Table 1.