Waikato Riverbed reveals active faults, University of Waikato researchers say

There may be more faults under Hamilton than previously thought. Photo / Google Earth

The bed of the Waikato River has revealed 25 potential fault lines and as many as four are active, University of Waikato researchers have found.

That meant there could be more shaking and more damage to infrastructure such as sewage pipes, roads, and other services, which would have implications for recovery after a serious earthquake.

Earlier studies found evidence for deep faults within the Hamilton Basin, and excavation in 2015 uncovered a potentially active fault at the surface within Hamilton City.

Since then Dr Vicki Moon and Dr Willem de Lange have examined the bed of the Waikato River between Cambridge and Taupiri using specialised echo sounders, finding 25 potential fault zones.

They believe at least four may be active.

Some of the faults could be linked to "low grade geothermal activity" between Templeview and Orini, and at Horotiu, as well as a patch of basalt volcanoes at Koromatua.

The four identified potentially active faults are Osborne Rd, Kukutaruhe Fault and two in the Te Tatua o Wairere Fault Zone.

The initial results indicate that the maximum earthquake magnitude for Hamilton remains the same, at 6.8. De Lange says the probability of an earthquake remains at the same low level, but their research indicates it is more likely to be localised.

De Lange said the Waikato Expressway uncovered several fault zones during excavation, and data is also being collected from those sites to better assess the possible magnitude and frequencies of earthquakes near the city.