Active Planet: Queensland sufferes 5.2 mag. 'quake

An earthquake of 5.2 on the Richter scale in North Queensland happened in a rural area some 50km outside the small cattle town of Bowen. It is important that it is classified as "an earthquake" because that defines it as a new event.

But not too far, in global terms, away a similar size event occurred in Christchurch, New Zealand. There a huge earthquake late last year was followed up by an another event in February. That one, a 6.3 magnitude event, caused more damage than the previous one - not because of its strength, but because it was at a much shallower depth. The February event was classified as an aftershock - there have been many hundreds since the 2010 earthquake - and later as an earthquake. Yesterday's 5.3 event is also being classified as an aftershock.

But not long afterwards, a 5.9 magnitude shock hit the same part of Japan as the 11 March event that caused such widespread devastation - and terminal damage to a nuclear plant. At 5.9, the event is itself serious but it is just the latest in a series of serious shocks to affect the region.

Whether this latest shock is responsible for the increased radiation levels found in the sea off the coast of the failed reactors earlier today remains to be seen.