I thought that what I read was there was more than one wave recorded, and they were identical when plotted visually.  Keep in mind, one sound as you put it, would still plot multiple waves, and the waveform when plotted wouldn't be consistent from the peak of one to the next.  If the waveforms were identical, there's no way they were naturally occurring.  Whether the frequencies were high or low is irrelevant to that point I believe. So if they recorded waves from a seismic event, each wave would be different from another.  It's not possible for them to be identical if they're naturally occurring, even if from the same source. Just like I can play the same note on the guitar more than once, but each note will plot to look different no matter how hard I try to make them identical, the earth can rub/grind/shift against itself multiple times in one seismic event and each wave will plot it's own fingerprint.