Japan earthquake vibrations nearly reached space

National Geographic : The vertical motion of the March 2011 megathrust earthquake and resulting tsunami in eastern Japan produced vibrations that affected Earth’s atmosphere—all the way up through the ionosphere. The vibrations at ground level were akin to low-frequency sound waves and didn’t travel far, writes Richard Lovett for National Geographic, but they expanded as they traveled upward through thinning air. Even at 30 000 feet, the level of commercial airline traffic, the waves from the disaster would have expanded to about three feet in amplitude and would not have been noticed by air passengers. In the ionosphere, however, the waves were amplified to thousands of times their original size, which compressed the gases therein enough to affect radio waves, such as those used for GPS. Whereas this process has been noted with other earthquakes, the waves from the Tohoku event have had the largest effect yet measured.