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8/6/2018 — Education, Science and Technology
Quake swarms in Rotorua-Taupo area

Earthquake swarms are typical of the earthquake activity in the Rotorua-Taupo area - the Taupo Volcanic Zone.

GeoNet reported that in the last week they have occurred near Kawerau and Taupo. There have been two swarms of small earthquakes located near geothermal systems - A small one near Taupo (Rotokawa geothermal system) and a slightly larger one at Kawerau. Both are large geothermal systems and local earthquakes are common.

On May May 31 GeoNet located nine earthquakes near the Rotokawa geothermal area. Their magnitudes ranged from about M 1.5 to M 2.5, while the depths ranged between 6 and 9 kilometres.

The swarm in the Kawerau area is larger and also started around May 31, with more events on June 2 and 5. The magnitudes ranged from about M 1.5 to M 1.9, while the depths ranged between 5 and 6 km for the events on May 31 and June 2.

Then, overnight June 5 two further phases of swarm activity occurred at Kawerau. In the first phase from 6 to 10 pm GeoNet located 54 events, the depths ranged 4 to 12 km and the magnitudes from 0.9 to 3.8.

The largest was at 7.22 pm. The second phase after 10 pm consisted of 41 events. The depths ranged 2 to 8 km and the magnitudes from 1.8 to 4.1.

GeoNet said the quakes are likely to be related to the long-term tectonic stretching of the Taupo Volcanic Zone.

“Swarms are often characterised by no one main or large event, with many of the events being about the same size. Currently, there are no indications that the earthquakes are related to volcanic activity,” GeoNet added.

Source: geonet.org.nz

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Seismic record showing the two phases of swarm activity near Kawearu. Source: GeoNet.