Aftershocks have continued overnight from Wednesday night's 5.6 earthquake at Taupō.
Dozens of quakes have been recorded since midnight on Thursday with a 3.9 tremor the largest. The shallow quake 20km south-west of Taupō hit at 5.37am.
Most of the aftershocks were too weak to be felt.
The initial 5.6 tremor was the biggest in the Lake Taupō region since a 5.0 earthquake in 2019.
It followed an increase of earthquakes in the region since May 2022 when current current period of unrest at the Taupō volcano began, GeoNet says.
Activity associated with magma and hydrothermal fluids inside the volcano is believed to be causing the recent seismic activity which could continue for weeks or months, GeoNet said.
GeoNet experts were still looking into the evidence of a potential seiche or small tsunami on the shorelines around Lake Taupō resulting from the earthquakes.
It was unclear whether signs of lake water being pushed onshore was due to a seiche, where the lake moves back and forth and sloshes, or a tsunami caused by a landslide, or a combination of both, GeoNet said.
Tsunami-type waves in lakes can be caused by earthquakes, landslides, or even weather conditions, and records showed they had occurred in the past at Lake Taupō.
In response to the increase in volcanic unrest GeoNet had raised the volcanic alert level from 0 to 1.
RNZ
