Shorter Days: Earth Now Rotates Faster
“Using a complex model to perform a theoretical calculation based on a U.S. Geological Survey, Richard Gross of NASA’s Jet Propulsion Laboratory (JPL) has determined that by changing the distribution of the Earth’s mass, the earthquake that devastated Japan last Friday should have sped up the Earth’s rotation, resulting in a day that is about 1.8 microseconds (1.8 millionths of a second) shorter.
The calculations, which will likely change as the data on the Japan quake is further refined, have also been used to examine the effects of other recent quakes.
Gross estimated that last year’s 8.8 earthquake in Chile shortened the length of a day by about 1.26 microseconds, while similar calculations revealed the 9.1 magnitude Sumatran quake of 2004 shortened the day by 6.8 microseconds.
Just how much an earthquake affects the Earth’s rotation depends on the magnitude of the quake, its locations and details of how the fault slipped.”