The megaquake connection: Are huge earthquakes linked?

The recent cluster of huge quakes around the Pacific Ocean has fuelled speculation that they are seismically linked. New Scientist examines the evidence

AT 2.46 pm local time on Friday last week, Japan shook like never before. The magnitude 9.0 earthquake wrenched the main island of Honshu 2.5 metres closer to the US and nudged the tilt of Earth's axis by 16 centimetres. At the epicentre, 130 kilometres offshore, the Pacific tectonic plate lurched westwards, and a 10-metre-high tsunami sped towards the coastal city of Sendai and the surrounding region.

The devastation caused by the events is difficult to exaggerate - estimates suggest the number of fatalities could top 10,000. One of the few consolations is that quakes of magnitude 8.5 and above are rare: the Sendai earthquake is in the top 10 of the highest-magnitude quakes of the last 100 years.

Yet three of these - the December 2004 Sumatra quake, the February 2010 Chile quake, and now Sendai - have struck in just over six years. This presents a horrifying possibility: that there is a link between these megaquakes and that, as a result, more could strike.