Seismologists believe they have pinpointed the source of a mysterious low-frequency ”hum” that emanates from the Earth, the British science journal Nature reports in Thursday’s issue.
The persistent noise — at between two and seven milliHertz, way below the threshold of human hearing — is clearly caused by large emissions of energy near or at the Earth’s surface.
But the puzzle is that the hum can be recorded on days even when there are no major earthquakes, the likeliest source for such massive energy release.
University of California at Berkeley experts Junkee Rhie and Barbara Romanowicz note that the hum orginates mainly in the northern Pacific Ocean during the northern hemisphere winter, and in the Southern Ocean during the southern hemisphere.
They suggest the hum is generated by interaction between atmosphere, ocean and sea floor.
Storm energy in the winter is converted to deep ocean waves which then interact with the seabed, creating vibrations that cause the hum, they theorise. – Sapa-AFP