Earthquake swarm rattles Central Volcanic Region of New Zealand

Located in the Central Volcanic Region, the town of Kawerau in New Zealand has been hit by a series of earthquakes since March 17, 2023, with a tally of over 780 quakes. Of these, six earthquakes have registered magnitudes above M4.0. The seismic activity has caused noticeable shaking in the region, with the most substantial earthquake having a magnitude of M4.8, while the majority of the quakes have been rated between M2.0 and M2.9.

• While earthquake swarms are a common feature of the Central Volcanic Region in New Zealand, swarms with this number of M4 events are relatively infrequent.

Although the earthquakes are disruptive and disconcerting for the people in the area, it is a common occurrence in the Central Volcanic Region of New Zealand, with previous swarms happening in 2018 and 2019.

GeoNet stated that these quakes are in keeping with historical activity in the region, with the most likely scenario being for the swarm activity to continue decreasing over the next few days.

Experts believe that the swarm is tectonic in nature given the tectonic setting, history of swarm activity, and the normal-faulting mechanisms identified for some of the larger events.

The location of the swarm is outside a volcanic area, so there is no indication of volcanic unrest and no relation to the recent unrest at Taupō or Ruapehu, but there has been some landslide activity in the area related to these earthquakes, including rockfalls. This extent of landsliding is typical for M4-5 earthquakes, GeoNet said.

Landslides can be triggered by heavy rain or earthquakes and can occur with little or no warning, making homes near hills or steep slopes and cliffs most at risk. The ground is likely more vulnerable to landslides now due to the recent cyclone and rain, and many landslides from Cyclone Gabrielle are still visible. It is important to watch out for cracks or movements that could be warning signs and get quickly to safety.

Civil Defence has advised the public on what warning signs to look out for, and to contact 111 if in immediate danger or to call the local council. Despite the high number of quakes, the most likely scenario is for the level of seismic activity to decrease over the coming days to weeks.

References:

¹ Kawerau Earthquake Swarm – GeoNet – March 19, 2023

Featured image credit: GeoNet