The northern part of New Zealand has been shaken by a strong earthquake this morning.
The 5.1 magnitude quake hit at a depth of 7km about 5km south of Te Aroha in the Waikato region at 5.39am.
More than 20,000 people reported feeling a shake in the areas nearby, including Hamilton, Tauranga, Auckland, and Rotorua.
"When an earthquake occurs there is always a small possibility that a larger earthquake will follow," GeoNet said on its website. "However the most likely scenario is that there will be a number of smaller aftershocks which will taper off with time."
The early morning quake was followed by nine aftershocks in the same area, with the biggest being a moderate 3.9 magnitude at 11.21am.
A shallow M3.9 aftershock was felt by >2.9k folks across Waikato and Coromandel. This was likely on the same fault system as this morning’s M5.1 and the M3.9 last week.— GeoNet (@geonet) January 3, 2023
We expect aftershocks like this to occur over the next hours and days, with frequency and size tapering off. pic.twitter.com/pQZn4ODifm
About 8000 people reported feeling the first aftershock, and about 4000 reported feeling the second.
Lana from Tauranga told Summer Times she thought it was oddly quiet this morning, when there would usually be birdsong coming from her garden.
"Then suddenly, there was this enormous shake and I thought 'oh, I'll just ride this one through', but then I could hear everything rattling in the house and then it got a little bit stronger it seemed and my crystal in china cabinet started to rattle madly.
"There was a kind of a twist and a rock to the quake and I thought this is getting serious, I thought I've got to get out and get under the door frame and as soon as I leapt out, it stopped."
It felt similar to the 1987 Edgecumbe 6.5 magnitude earthquake, which struck Bay of Plenty, she said.
"I was getting concerned because it was getting that kind of roll, that kind of twist going to it."
Truck driver Darryn Phayer said his 25-tonne truck swayed sharply in the first earthquake.
"The truck started violently shaking and I thought 'oh what's going on here', but literally, prior to that, in the farm across the road from the yard, a bunch of dogs started barking and I thought 'oh what's upset them' and within a couple of minutes, it was up on GeoNet.
"[It] scared the living daylights out of me, to be honest."
On the east coast, Pauanui resident Christine Harrison said it was the strongest quake she had ever felt.
"It was a strong jolt in that it made me grab the edge of the bed to really hold on but as quickly as it started, it stopped."
It comes after a 3.9 magnitude quake in the same area last week.
GeoNet said they were likely on the same fault system, near the Kerepehi Fault which is part of the Hauraki rift zone.
It said this was a good reminder to always be prepared for a large earthquake.
Only six earthquakes larger than a 3.0 magnitude occurred between Tauranga and Hamilton in the last ten years, GeoNet said.
But there has been strong shaking in the past with a 4.9 magnitude earthquake in Te Aroha in 1972, GeoNet said.
A 1972 bulletin, published by the New Zealand Society for Earthquake Engineering, reports a '5.1 magnitude' quake in the area, with damage confined to the region but also felt as far as Mangakino and Whakatāne.
There was also said to be numerous aftershocks the next month.
The quakes are likely on the same fault system, the area last having a strong quake in 1972 with the M4.9 Te Aroha earthquake, and a reminder that earthquakes can occur anywhere in New Zealand at any time. In the event of a large earthquake: Drop, Cover and Hold. pic.twitter.com/vnuJgo5k9C— GeoNet (@geonet) January 3, 2023