Record sections of synthetic (top panels) and observed (bottom panels) waveform stacks. Synthetic Instaseis (van Driel et al. 2015) PP (a) and SS waveform stacks (b), respectively, are computed for model IASP91 (Kennett & Engdahl 1991), 100 randomly picked events, and 10 stations per event. Partial stacks are computed as a function of epicentral distance in 1°-bins. Blue/red colours indicate positive/negative amplitudes, respectively. Traveltime curves for PP/SS and their underside reflections (precursors) are shown in green and interfering phases in black, respectively. Observed PP (c) and SS (d) waveform sections, respectively, illustrated for the cap with the largest number of bounce points (cap #22) without muting of interfering phases.