Geologists analysing Tuesday’s devastating earthquake say it is probably related to the one which rocked the city on September 4.

The 6.3 magnitude quake was significantly lower on the Richter scale than last year’s, but far closer to the earth’s surface and centred nearer Christchurch city.

Hazard management lecturer Tom Wilson from Canterbury University says because of the different nature of the quake, the impact affects completely different areas.

"The reason this time the damage has been so bad is that it was much shallower - only 5kms from the surface.

"So the energy radiating out from the rupture would have been much stronger when it reached the surface."

Tom Wilson says the two earthquakes are well within the seismic ‘zone of relativity’ and are therefore probably linked.

"The problem is that it was a very large event in it's own right.

"It's highly likey to be related to the September Earthquake, it's well within the sphere of influence of the crush movemeny the previous earthquake caused.

"But, because it's so large, it will set off its own set of artershocks, which we are seeing now and will do for the next few weeks."

Russ van der Sant, a Geologist at GNS, says his team has been flat out since the quake trying to get more details on the actual event.

"The earthquake that happened probably released 20 times less energy than the September shock but because it was so much closer it actually gave Christchurch a much bigger jolt.

"It’s like light a light bulb...if your close to it, it can be very bright and that’s what happened.

"It was so much closer to Christchurch that it gave it a really big kick and that's what sent most of those buildings over the edge."

GNS says it’s still gathering data from their strong motion sites around the South Island.

For more info on the size and locations of the quakes, plus aftershock data, head to the GNS site, here.