A swarm of small earthquakes continues around Whakaari/White Island, but so far there’s no indication the quakes are connected to the volcano. Since Thursday, GeoNet has recorded more than 300 earthquakes, centred 20km deep or less, under the sea surrounding the Bay of Plenty island. Most have been to the west and south, and the largest had a magnitude of 3.9. GNS Science volcano information specialist Brad Scott said scientists were not aware of anything in particular that had set the swarm off.
It wasn’t known whether the location of the swarm close to the island was just coincidence, or whether there was some sort of relationship.
For now there was no indication of any volcanic activity on Whakaari/White Island, Scott said. “We’re not seeing any response from the volcano.“
The type of earthquakes in the swarm were of the tectonic type, where cold, brittle rock was being broken.
Earthquake swarm processes were not fully understood. In this case, sequences of a main shock followed by aftershocks were being repeated.
About half a dozen of the quakes had been of magnitude 3.5 or more. “As earthquakes they’re still very small,” Scott said.
Whakaari/White Island was part of the Taupō Volcanic Zone – which also included Mt Ruapehu, Taupō and Rotorua – where earthquakes were very common.
GeoNet has warned that the swarm could increase the risk of landslides on the island, as the earthquakes are shallow and local material is relatively weak.
On Monday morning, the volcanic alert level at the island remained at 1, indicating minor volcanic unrest.