shorter days

A new analysis of the 8.9-9.0 magnitude earthquake in Japan has found that the intense temblor has accelerated Earths spin, shortening the length of the 24-hour day by 1.8 microseconds, according to geophysicist Richard Gross at NASAs Jet Propulsion Laboratory in Pasadena, Calif. Gross refined his estimates of the Japan quakes 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 planets mass. A microsecond is a millionth of a second."

By changing the distribution of the Earths 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 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.

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 planets mass distribution such as the seasonal shift of the jet stream.

The initial data suggests Fridays earthquake moved Japans main island about 8 feet, according to Kenneth Hudnut of the U.S. Geological Survey. The earthquake also shifted Earths figure axis by about 6 1/2 inches 17 centimeters, Gross added.

via The Manila Bulletin Newspaper Online.