"Most earthquakes send out waves with a slew of different frequencies, but Mayotte's signal was a clean zigzag dominated by one type of wave that took a steady 17 seconds to repeat." https://www.google.com/amp/s/relay.nationalgeographic.com/proxy/distribution/public/amp/science/2018/11/strange-earthquake-waves-rippled-around-world-earth-geology I would expect different frequencies kind of all over the place in a naturally occurring seismic event - because unlike music, it's not controlled.  It was one dominant frequency and the time passed from one valley or trough to the next was a steady 17 seconds.  Which is also weird for a seismic event.  The frequency wouldn't stay so steady for so long.  I'd be surprised if any seismic event had any steady frequencies to it at all to begin with much less for the amount of time it would take to record multiple waves moving at 17 second intervals.  17 seconds is a long time.  That's a long time to produce consistent and steady waves.  So the frequency was extremely steady...which is actually more likely in the world of music.. it wouldn't make sense because the earth can't run/grind against itself exactly the same way over and again in the same event.  That's not feasible in the natural world. To the point that it was picked up across the world, that's because the frequency was so low...lower frequencies travel further.  It's the same reason you can hear the bass from someone's music from further away than you can hear the guitars or cymbals.