People in Opito Bay, at the eastern end of Kerikeri Inlet, reported feeling some of this week's cluster of quakes. Photo / Supplied
Northland isn’t known for earthquakes, but now and then the region reminds scientists it still contributes to this country’s reputation as the Shaky Isles – as it did this week.
Northlanders have been active on social media since Sunday, swapping their accounts of strange jolts and sudden bangs they suspected – though weren’t sure – might have been earthquakes.
Yesterday GNS confirmed there had been six small quakes in Northland, five of them between March 1 and March 4, centred in the Kerikeri inlet, about 60km northwest of Whangārei as the crow flies; the other near Moerewa, about 55km northwest of Whangārei.
Earth Sciences New Zealand (ESNZ) seismic duty officer Sam Taylor-Offord said since the service expanded its earthquake monitoring network in 2022, it had recorded a total of 10 earthquakes in Northland – about three per year.
The most notable – ironically because of its small magnitude – was the 1.6-magnitude tremor near Peria last September.
In the last month, the network had not “detected” any earthquakes in the region. However, ESNZ scientists manually recorded six earthquakes this week. All were about 5km deep.
Two of the Kerikeri Inlet quakes were recorded on Tuesday, March 3. The larger was magnitude 2.1, at 5.05pm. Another at 8.59pm measured magnitude 1.8.
Two more in the inlet on March 2 measured magnitude 1 (at 3.38am) and magnitude 1.3 (at 8.40am).
On March 1, there was a magnitude 2 earthquake in the inlet.
The quake near Moerewa struck on March 2, measuring 1.4.
Taylor-Offord said it was “not unusual” that these earthquakes, although felt in Northland, were not automatically recorded by GeoNet. They were small in magnitude and occurred at the margins of the monitoring network.
“While GeoNet didn’t detect the recent events this week automatically, they were recorded in high-fidelity on the local network. From that data, our team at the 24/7 National Geohazard Monitoring Centre has precisely located where they occurred and has manually added five earthquakes near Kerikeri to our catalogue.
“These events correspond to reported times of shaking around Opito and Doves Bay in recent days. We are now looking to see if there are more earthquakes in the sequence.
“We are grateful for the direct reports we have received from the region. Feedback like this helps us update our catalogue more accurately around these margins.
“Northland is far from the active plate boundary, where the Pacific plate is subducting [moving] under the Australian plate. For that reason, there isn’t much stress accumulating in the crust, which is what we expect for a tectonically stable region like Northland.
“However, these recent events are a reminder that earthquakes can happen in the region. In fact, the most significant events recorded in Northland occurred between 1963-1964 when a period of seismicity produced a magnitude 4.8 and many smaller earthquakes in the same area,” Taylor-Offord said.
A similar reminder came last year when a rare magnitude‑1.6 quake near Kaitāia – the first in that area since the 1960s – prompted fresh curiosity about Northland’s dormant faults. At the time, ESNZ scientists said the micro‑quake highlighted how even in a tectonically “quiet” region, small amounts of stress can still build in the crust, and that more sporadic, low‑level quakes are likely as old faults occasionally release energy.
Taylor-Offord said earthquakes had been recorded in Northland between 1964 and 2022. The challenge for GeoNet, the business arm of ESNZ, was that while the region gained a few more seismometers in 2022, the national monitoring system was still tailored to detect large or impactful earthquakes, with denser coverage in high-seismic regions like volcanic zones.
“These events are a good reminder that we should expect earthquakes everywhere in New Zealand,” he said.
Recent research has also revealed how much remains unknown about seismic hazards in the upper North Island. A major Auckland study has identified dozens of previously unmapped faultlines beneath the city, prompting trenching investigations to determine whether any have moved in the past 125,000 years – the threshold for being considered active.
Sarah Curtis is a news reporter for theNorthern Advocate, focusing on a wide range of issues. She has nearly 20 years’ experience in journalism, most of which she spent court reporting in Gisborne and on the East Coast.