'Moderate' 6.1m earthquake reported off east coast
Saturday, 6 March 2021
Earthquakes are continuing to rattle the North Island’s east coast on Saturday.
A magnitude 6.1 shake was reported at 1.16pm on Saturday. GeoNet said the earthquake struck 140km east of Te Araroa at a depth of 33km, and called it “moderate”.
A number of smaller shakes, with magnitudes ranging from 5.4 to 3.4, occurred on Friday night and throughout Saturday, to the east of Te Araroa.
Some seismic activity in the country's north-east is to be expected after Aotearoa was rattled by three large earthquakes on Friday, which struck near the Kermadec Islands, and triggered tsunami warnings and evacuations in Northland and coastal Bay of Plenty towns.
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On Friday, more than 50,000 people reported the first large shake which happened 100km east of Te Araroa. Two other quakes that followed were well to the north of Aotearoa in the vicinity of the Kermedec Islands, reaching magnitudes of 7.4 and 8.1.
By Friday afternoon however, the risks were downgraded with evacuees allowed to return to their homes. Minimal damage has been reported so far.
On Saturday, more than 1050 people reported feeling the 6.1m shake to the east of Te Araroa. In the hour afterwards, a number of “weak” earthquakes were also reported by GeoNet, ranging from magnitude 5-4.6.
It's expected there will be further seismic activity over the next coming weeks. Speaking on Friday, University of Otago earthquake science chairman Mark Stirling explained while the three significant earthquakes were along the Hikurangi Subduction Zone, the earlier quake off the East Cape was part of a separate event.
“I think there will be aftershocks, but they’ll be a lot smaller than the main shock. They won’t be as significant or as ground-shaking.”
He said they would probably only be short-lived and last for a matter of weeks, whereas other fault lines could cause aftershocks lasting years – like what happened in Canterbury.
“People just need to remember we live in the Shaky Isles,” Stirling said.
In a forecast published online on Friday night, GeoNet said that while no-one can scientifically predict earthquakes, it can provide forecasts of future earthquakes using computer models that are updated as an earthquake sequence continues.
GeoNet forecasts that for the surrounding area of the 7.1m East Cape earthquake, there is a 69-85 per cent chance that one or more 6.0-6.9m earthquakes could occur within the next 30 days.
Following the Kermadec events, GeoNet also developed three scenarios for what earthquakes may happen over the next 30 days based on forecast models.
The most likely scenario is that further earthquakes of a smaller magnitude will decrease in frequency over the next 30 days.
This includes the potential for earthquakes in the 7.0-7.9m range (more than 80 per cent probability within the next 30 days).
“We expect there to be more felt earthquakes, particularly in the East Cape.”
Although the main warnings have been cancelled, officials still recommend people remain vigilant and take extra precautions with beach and ocean activities due to possible strong unusual currents and unpredictable surges.