Rolling shutter artifacts - Shutter speed test

Bombardier Q400 propeller while cruising as seen through a Canon 5D Mk II while varying the shutter speed from 1/30 sec to 1/4000 sec and back. (Interesting to note that, even at the low shutter speed end, there are resonance artifacts at most speeds, but not so much at 1/40 sec and 1/80 sec. I'm guessing the rotation speed is a roughly a multiple of 15 but not 2?)