There are significantly more fault lines under Hamilton than previously thought.
Researchers from the University of Waikato have discovered 25 potential fault zones in the Waikato River bed between Cambridge and Taupiri, four of which may still be active.
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Earlier research indicated just three or four fault lines in the area.
Dr Willem de Lange, who carried out the research along with Dr Vicki Moon, told Newshub that the faulting under Hamilton splits off "like a head of broccoli" near the surface, sending many smaller fault splays off in different directions.
This means it's more difficult to predict where the fault lines could rupture and plan city layouts accordingly.
Because the fault segments are shorter than previously believed (earlier research assumed they spanned the length of the Hamilton Basin), the amount of energy they can release is reduced.
The new findings indicate earthquakes are more likely to be localised and less life-threatening, but shaking might be more intense resulting in greater damage to infrastructure like sewerage pipes and roads.
Dr de Lange says the next phase of the university's research will be "trying to unravel the tectonic structure of the North Island".
"Something significant is happening in the deep structure somewhere between Auckland and Hamilton," he says, citing how fault lines split under Auckland.
"Something funny is happening."
He says the research into fault lines is "another piece of the puzzle" and hopes it can be used to answer questions about the island's earthquakes.
Initial research results show that despite the discovery of the fault lines, Hamilton's maximum earthquake magnitude remains the same.