JAPAN -- The massive earthquake that struck northeast Japan last March 11 has shortened the length Earth's day by a fraction and shifted how the planet's mass is distributed.
A new analysis of the 8.9-9.0 magnitude earthquake in Japan has found that the intense temblor has accelerated 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.
Gross refined his estimates of the Japan quake's impact - which previously suggested a 1.6-microsecond shortening of the day - based on new data on how much the fault that triggered the earthquake slipped to redistribute the planet's mass. 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. More refinements are possible as new information on the earthquake comes to light, he added.
The scenario is similar to that of a figure skater drawing her arms inward during a spin to turn faster on the ice. The closer the mass shift during an earthquake is to the equator, the more it will speed up the spinning Earth.