Earthquake swarm south-west of Kawerau

Published: Wed Mar 13 2019 11:00 AM

Early this morning, GeoNet began registering an earthquake swarm south-west of Kawerau in Bay of Plenty.

The swarm started around 5am on Wednesday 13 March and is still occurring. We have located 46 earthquakes at the time of publication, although more have occurred that are too small to be reliably located. The swarm earthquakes range in magnitude from 1.2 to 3.7 and all occur in the upper 20 km of the crust, with some events being in the upper 5 km.

Map showing the location of the earthquake swarm south-west of Kawerau

Map showing the location of the earthquake swarm south-west of Kawerau

The larger events in the swarm have been felt locally. The largest event, which occurred at 6:21am, was reported ‘felt’ by 173 people, with most reporting it as weak-to-light shaking.

Swarm activity like this is typical in the Taupo Volcanic Zone, and this swarm is akin to previous swarms in the greater Rotorua-Kawerau area.

“While this swarm is occurring in an area of active volcanism, the characteristics of its earthquakes are similar to those of a tectonic swarm, leading us to hypothesise that the swarm is not volcanically-driven”, says GNS Science Duty Seismologist Sam Taylor-Offord.

Mt Tarawera drum plot showing swarm activity

Mt Tarawera drum plot showing swarm activity

Often earthquake activity in the Taupo Volcanic Zone occurs as short-lived clusters that are known as ‘swarms’. They are very common in the Rotorua-Taupo area and larger swarms have lasted weeks-to-months and have included many hundreds of earthquakes.

So, what is a “swarm”?

Swarms are clusters of earthquakes that are often characterised by no one main or large earthquake. Many of the earthquakes in a swarm are usually about the same size. Swarms are common in New Zealand, especially in volcanic regions.

Here are some links to GeoNet news stories on recent New Zealand swarms:

Northland

Turangi

Kawerau and Taupo

Science information – Brad Scott and Sam Taylor-Offord.

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