MASSIVE earthquakes, such as the one that triggered the Indian Ocean tsunami on 26 December 2004, could be predicted years in advance by monitoring tremors caused by 鈥淓arth tides鈥�.
The gravitational pull of the sun and moon deforms the Earth鈥檚 crust and upper mantle, creating bulges and dips in the planet called Earth tides. These can reduce the pressure on tectonic plates, causing them to slip past each other, inducing tremors.
Sachiko Tanaka of the National Research Institute for Earth Science and Disaster Prevention in Tsukuba, Japan, studied 1126 quakes that happened along the Sumatran fault, where the Eurasian plate slides below the Indo-Australian plate, between 1976 and 2008. He found that in the years leading up to the 2004 earthquake, more tremors occurred when the pull of the daily Earth tides was at its strongest than at other times. Tanaka saw the same signal in the run-up to two nearby massive quakes in 2005 and 2007 (Geophysical Research Letters, ).
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This tidal signal may help to identify areas that are likely to experience a huge earthquake in coming years, says at Columbia University in New York City.