Audio
See the previous seismogram's description for information about how seismic waves can propagate through water, and information about the spectrogram at the top.
The ambient noise level in the water column is much higher in this seismogram than the previous one, which masks the earthquake T-wave arrival in the center of the time span. On the spectrogram, there is very strong noise at 5 Hz and 10 Hz shown by the bright red streaks going right across the spectrogram. This is probably propeller noise from a ship passing near the hydrophone. The ship noise makes the loud, chord-like two-toned sound that you hear. On top of that, there are many higher frequency sources of noise above 10 Hz, shown by fainter yellow streaks going across the spectrogram. Their source is a mystery, but they do not mask the sound of the T-wave arrival from the earthquake midway through the seismogram. It makes a very distinct, broad-band whoosh, though you can barely see it above the increasing noise in the seismogram. The T-wave shows up as the splash of yellow color midway through the spectrogram.
| Earthquake recorded by hydrophone Audio |
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Data courtesy PMEL/NOAA.