http://www.wired.com/wiredscience/2009/08/hummingearth/
In an upshot, theres a constant roughly 10 millihertz hum worldwide, detectable by seisometers, that goes up and down. its created by... WAVE ACTION. that is, waves in the ocean. And its rise and fall and appearance in different areas inland is caused by storms and such moving main masses around. Thought some here might find that interesting, in comparison to THE HUM.
