A group of scientists is mapping a section of the lower North Island to get a clear picture of what's going on beneath Wellington.
Scientists from Victoria University, GNS Science, Tokyo and California are placing 900 seismic devices from Wairarapa to Kapiti Coast.
Professor Tim Stern of Victoria University says the images could give the scale of friction between tectonic plates in this region.
He says old volcanoes under ground can jam some plates - causing large earthquakes.
Once the testing is complete, Professor Stern says the results could take a year to collate.
