Hundreds of little earthquakes are causing ground deformation at Lake Taupō, GeoNet says.
The movement under the active volcano has caused the ground to uplift and distort.
Scientists found a swarm of small earthquakes causing tremors underneath Lake Taupō at a rate of 30 quakes per week.
They have been monitoring the spate of earthquakes in the volcano which has been seismically active since 2000, with more than 5000 earthquakes recorded.
Since the start of May, there have been more than 490 earthquakes shallower than 30km below the surface.
The greater Rotorua-Taupō area (Ahi Tupua) is an active volcanic environment, with the quakes mainly located around the Karangahape Cliffs and northeast of Horomatangi Reef.
The earthquakes have ranged in size from about magnitude 1.0 up to 3.6 with many people in the area not feeling the tremors.
GeoNet observations in June showed 12mm of uplift from the ground and recent measurements have indicated a horizontal deformation on the lake.
GeoNet Volcano Science Operations Specialist Yannik Behr said they believe the earthquakes and ground deformation are similar to swarms of small earthquakes in 2008-2009 and 2019 and therefore have kept the Volcanic Alert Level at Level zero.
"While the observations beneath Lake Taupō to date represent an increase to the normal background activity, they do not stand out with respect to previous periods of unrest in 2008-2009 and 2019," Behr said.
Because the volcano is active, GeoNet said uplift or sinking of the ground in the area will continue to occur in the future.
