Japan quake may have shortened Earth days

Wed, 03/16/2011 - 6:46am



The calculations also show the Japan quake should have shifted the position of Earth's figure axis by about 17 cm (6.5 in), towards 133 degrees east longitude. Earth's figure axis should not be confused with its north-south axis; they are offset by about 10 m (about 33 ft). This shift in Earth's figure axis will cause Earth to wobble a bit differently as it rotates, but it will not cause a shift of Earth's axis in space—only external forces such as the gravitational attraction of the sun, moon, and planets can do that.


In comparison, following last year's magnitude 8.8 earthquake in Chile, Gross estimated the Chile quake should have shortened the length of day by about 1.26 microseconds and shifted Earth's figure axis by about 8 cm (3 in). A similar calculation performed after the 2004 magnitude 9.1 Sumatran earthquake revealed it should have shortened the length of day by 6.8 microseconds and shifted Earth's figure axis by about 7 cm, or 2.76 in. How an individual earthquake affects Earth's rotation depends on its size, location, and the details of how the fault slipped.







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