One of the causes of unusually violent shaking in the Canterbury earthquakes could be present as far south as Dunedin, a GNS seismologist says.
Dr Martin Reyners, of Wellington, received a $717,391 grant through this year's Marsden Fund for research to find the southern boundary of the Hikurangi Plateau and whether the plateau affected Otago tectonics.
Dr Reyners said finding the southern boundary of the plateau was important because it had an effect on how violent shaking was in earthquakes.
''Research we have done on the Canterbury quakes shows that one of the reasons the shaking of the earthquakes was so strong ... was that this plateau ... underlies that area at about 10km depth,'' he said.
If the plateau was also underneath Otago, a large quake in the region could cause more damage than would normally be expected.
''What we would like to do for the engineers, say for engineers working in Dunedin for example, is to tell them if we had an earthquake what type of shaking we would expect.
''At the end of the day, we try to inform better building codes,'' he said.
The study involved installing 20 portable seismographs in locations from Dunedin to South Canterbury.
The seismographs would be used to record activity for a year and GNS would then spend the next two years analysing what was recorded.
Dr Reyners said there was already evidence the plateau went as far south as Oamaru.
''In 1876, there was a sequence of two earthquakes near Oamaru ... and they were both just under magnitude 6. They have a very uncanny resemblance ... to what happened in Canterbury,'' he said.
For their magnitudes, the earthquakes caused an unusual amount of damage to buildings.
The plateau resulted in more violent earthquakes because it was made up of strong rock.
''Earthquakes are all about strain building up in the crust and then being released in an earthquake, and because these rocks are very strong they can actually store more strain before they break,'' Dr Reyners said.
This meant earthquakes in areas where the plateau was present were likely to be less frequent, but when they did happen they had ''a lot more energy'' than in places where the crust was weaker.
Dr Reyners said the research would also reveal more about the geological history of Otago, including why gold was abundant in parts of the region.
