GNS: Volcanoes keep quiet amid earthquakes

Scientists have observed little effect on New Zealand's volcanoes following the quakes. Photo / File

Did the Kaikoura earthquake and its aftershocks disturb our volcanoes?

GNS Science volcanologists say no, although monitoring equipment has picked up a recent series of seemingly unrelated tremors.

Volcanologist Brad Scott said there was a "brief bit of activity" at the submarine Monowai volcano north of Auckland over 24 hours on November 11 and 12 - a spate typically seen each month.

Levels of volcanic tremors also remained low at Raoul Island and White Island.

On land, the Okataina Volcanic Centre appeared quiet, with just a few small shallow earthquakes near Kawerau and a half dozen to the south in Waikite Valley, a place no stranger to small earthquake swarms.

There were also a couple of earthquakes near the Wairakei geothermal system, Scott said.

The Taupo Volcanic Centre remained quiet, with just two quakes this week.

"However, it is a very different story north of Kuratau [near Turangi], which experienced a sequence of earthquakes between the 10th and 13th of November."

The sequence came in four parts: the first, which included the largest earthquakes, started on November 10 and appeared as a typical main-shock after-shock sequence.

The largest of the 27 earthquakes was a magnitude 3.3.

After what Scott called a "geological power nap" - of about 21 hours, the second sequence started.

"It behaved much more like a typical Taupo Volcanic Zone swarm and included 52 earthquakes," he said.

The third part of the sequence started about 11 hours after the second and was also swarm-like, with 32 separate earthquakes.

"The fourth part included three magnitude 3 earthquakes and an isolated magnitude 3.2 earthquake on the eastern side of the lake."

This part dropped off before midnight Sunday and Monday and so far had not notably reactivated following the 7.5 Kaikoura quake.

The earthquakes ranged in magnitude from a little less than 1.0 to 3.3, and were between 5 and 11km deep. Most were 7-8km deep.

"Small shallow earthquakes like these will be well felt by local residents and we have received many felt reports from the area."

It was not clear if the sequence has finished yet, and prolonged earthquake swarms were a regular feature of the Taupo Volcanic Zone.

One near Matata in the mid-2000's lasted several years.

Further south, the Tongariro-Ngauruhoe area was "very quiet", with just a couple of small earthquakes, and the volcanic tremor at Ruapehu was slowly declining towards normal background levels.

"The lake temperature is now 31C, slowly declining from the recent maximum of 39C."

Mt Taranaki continued its silent watch over the West Coast of the North Island, he said.