Minor volcanic unrest continues at Taupō Volcano, with ongoing earthquakes and ground deformation.

The Volcanic Alert Level for Taupō Volcano remains at 1 (minor volcanic unrest).

The earthquakes and deformation at Lake Taupō have continued since the last bulletin on September 28, says GNZ duty volcanologist Agnes Mazot.

"The rate of earthquake activity has varied since May, peaking with over 80 events in a week in early September.

"The currently weekly rate has dropped noticeably from a plateau of about 20-40 events a week from June to September.

"Meanwhile our GNSS (GPS) instruments around the lake continue to observe uplift since May at a site on Horomatangi Reef in the centre of the lake."

Agnes says they have now located 746 earthquakes, mainly at a depth of 4 to 13 km beneath the centre of Lake Taupō since the activity began in May 2022.

The earthquakes in the last two weeks have been concentrated in the eastern part of the lake.

The largest was magnitude 3.3 on October 3.

In addition to seismic activity, GeoNet continuously monitors ground deformation (land movement) around Lake Taupō, says Agnes.

"Our GNSS (GPS) instruments around the lake continue to observe uplift at a rate of approximately 60 ± 20 mm per year since May 2022 at a site on Horomatangi Reef in the centre of the lake.

"An independent survey of vertical ground movement around the lake shore on 28 September shows that the Horomatangi Reef area had risen 24 mm since February 2022.

"This independent verification of analysis of GNSS data gives us a lot of confidence in our ground deformation results.

"We interpret the ground uplift and earthquake activity to be caused by the movement of magma and the hydrothermal fluids inside the volcano."

Agnes says this activity could continue for the coming weeks or months at varying rates or intensities.

"While some of the earthquakes may be felt in areas around Lake Taupō, the deformation is currently only detectable by our sensitive ground-based monitoring instruments."

Volcanic unrest is when magma or magma-heated hot water and steam forces its way through the ground beneath a volcano, producing earthquakes and ground movement.

There have been 17 previous episodes of unrest at Taupō over the past 150 years and none have ended in an eruption.

Check out more about this in our recent Q&A about Taupō volcano.