Japan Earthquake Vibrations Nearly Reached Space
Amplified sound waves shook Earth's upper atmosphere, study says.
(See: "Japan Tsunami: 20 Unforgettable Pictures.")
The vertical motion of the ground shaking and swelling tsunami waves produced the vibrations, which pressed upward against the overlying air, said Emile Okal, a geophysicist at Northwestern University who was not part of the study team.
This process has been known from previous earthquakes, but the vibrations from Japan caused the biggest such effect yet measured.
At ground level, such vibrations—akin to low-frequency sound waves—are very small, only about the size of the vertical motions that produce them. But as the waves travel upward into ever thinner air, they expand, Okal said.
At heights where airplanes travel, about 30,000 feet (9,100 meters), Okal said, the waves
