© NOAAA GNS plot of the energy dispersal from the 7.6 magnitude earthquake.
Thursday morning's submarine earthquake near the Kermadec trench sent most of its energy east and west, rather than south towards New Zealand say GNS scientists.
The earthquake was magnitude 7.6 and occurred in the Pacific tectonic plate close to the Kermadecs. The epicentre was 160km from Raoul Island and 920km from Tonga.
The orientation of the earthquake's fault rupture was north-south and most of the tsunami energy radiated perpendicular to the fault plane.
The largest observed peak-to-trough wave-height caused by this was 1.9 metres at the two tsunami gauges at Raoul Island, operated by GeoNet. This puts the top of the wave at about one metre above the normal tide level.
GNS Science tsunami scientist Dr William Power says small tsunami arrivals, not much larger than normal 'sea noise', were subsequently observed on tsunami gauges at Great Barrier Island and East Cape.
"The mechanism of the rupture was that of a normal fault, rather than a subduction thrust event, but both can produce a large vertical movement of the seafloor."