Japan earthquake shortened days on Earth - The massive earthquake that hit northeast of Japan on Friday (March 11) not only caused disaster (Read: The Worst Japan Nuclear Disaster) but also has shortened the length Earth's day by a fraction and shifted how the planet's mass is distributed.
Research found that the 8.9-magnitude earthquake in Japan has affected to the acceleration of Earth's spin, shortening the length of the 24-hour day by 1.8 microseconds, according to geophysicist Richard Gross at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Previously, Richard Gross estimated that Japan’s quake will give the impact of 1.6-microsecond shortening of the day, but based on new data on how much the fault that triggered the earthquake slipped to redistribute the planet's mass, 8.9-magnitude earthquake in Japan shortened time of day around 1.8 microseconds. A microsecond is a millionth of a second.
"By changing the distribution of the Earth's mass, the Japanese earthquake should have caused the Earth to rotate a bit faster, shortening the length of the day by about 1.8 microseconds," Gross told SPACE.com in an e-mail.
One Earth day is about 24 hours, or 86,400 seconds, long. Over the course of a year, its length varies by about one millisecond, or 1,000 microseconds, due to seasonal variations in the planet's mass distribution such as the seasonal shift of the jet stream.
The initial data suggests Friday's earthquake moved Japan's main island about 8 feet, according to Kenneth Hudnut of the U.S. Geological Survey. The earthquake also shifted Earth's figure axis by about 6 1/2 inches (17 centimeters), Gross added.
The Earth's figure axis is not the same as its north-south axis in space, which it spins around once every day at a speed of about 1,000 mph (1,604 kph). The figure axis is the axis around which the Earth's mass is balanced and the north-south axis by about 33 feet (10 meters).
"This shift in the position of the figure axis will cause the Earth to wobble a bit differently as it rotates, but will not cause a shift of the Earth's axis in space - only external forces like the gravitational attraction of the sun, moon, and planets can do that," Gross said.
