Moon and rain could mean quakes

A full moon may have triggered the Indian Ocean earthquake that caused the tsunami on 26 December 2004, a new study concludes.

Between October 2004 and August 2005 Robin Crockett from the University of Northampton, UK, and his colleagues monitored tremors and collected tidal data along the Java/Sumatra trench. They found that major quakes were 86 per cent more likely around new and full moons, when tides are at their greatest.

"At new and full moons the biggest mass of water is being loaded and unloaded at the plate boundary," Crockett says. That might be the final push that initiates a quake.

Meanwhile Sebastian Hainzl from the University of Potsdam, Germany, and his colleagues have noticed that rain can also trigger quakes. In 2002 they monitored tremors, rainfall and groundwater pressure in south-east Germany.

They found that water from a heavy rainstorm can reach spots underground where masses of rock are trying to move past each other but are stuck together by friction. The water can ease the friction, releasing pent-up tension so that the rocks jerk past each other and initiate tremors as deep as 4 kilometres