A 4.9 quake that rattled New Plymouth this afternoon struck in an area where big shakes are rare – just a dozen over 4.0 have been recorded there in 100 years.
Seismologists also say there's no direct link between the shallow, 2.35pm jolt and a series of quakes recorded off the coast of Levin last week, which included a 5.8 mainshock and a 5.2 aftershock.
Today's quake struck just 10km deep, about 35km north of the city, GeoNet reports.
Some residents said the shake was strong enough to knock objects off the wall.
New Plymouth-based Herald reporter Jamie Morton described the quake as a short, sharp and violent shake.
"Rather than the rolling quakes we've had over the last week, emanating from the lower North Island, this one struck very strongly – we felt our house move."
Dogs could also be heard barking across city suburbs after the quake, Morton said.
One young local, Daisy Marshall Kirkwood, 10, said: "My bedhead started shaking and the walls started jiggling."
One Twitter user said the earthquake caused "quite a lot" of photos to fall over.
Elsewhere, another user said there were two short but strong jolts which made items in the room they were in rattle.
Another person said they were watching the 1979 film Apocalypse Now when the earthquake struck, commenting: "Coincidence? I think not."
More than 3800 people have posted on Geonet saying they felt the earthquake. While most described it as being weak to moderate, six described it as "extreme".
• Widely felt 5.4 earthquake breaks GeoNet record
• More shaking: Magnitude 3.6 earthquake near Levin
• South Island earthquakes: 3.4 magnitude near Christchurch, 5.0 magnitude in Fiordland
• 4.7 magnitude earthquake jolts lower, central North Island including Wellington
It appeared the quake was the result of "strike-slip" faulting, where each block side slides past the other without uplift and down-thrust.
GNS Science duty officer Jonathan Hanson said it wasn't yet known whether the quake had hit on a known fault, of which there were a few in the area.
But Hanson said, in the past century, only 12 over 4.0 had been recorded there.
"So it's relatively uncommon, but not an unknown."
Hanson also said there were no geological links between today's quake and those which had been unfolding off the Lower North Island's West Coast over the past week.
"We are always looking for potential physical links, but I think this was more of a quirk of probability, that they happened at the same time."
More broadly, the New Plymouth quake struck within the Australian tectonic plate, where shallow, crustal faulting was constantly taking place, and its strength and proximity to the closeness to the surface explained why it was so widely felt.
The quakes off Levin, meanwhile, hit near the top of the subducting Pacific plate – something we could visualise as a huge inclined slab descending beneath the North Island.
This old, cold and rigid Pacific slab acted as a funnel that sent seismic waves across a wider area when a quake happened.
While quakes big enough to be felt are a relatively uncommon occurrence in Taranaki, several hundred quakes are recorded in the region each year – most of them in a region west of Mt Taranaki, called the Cape Egmont Fault Zone.
One new research programme, being led by GNS Science structural geologist Dr Hannu Seebeck, will use the Cape Egmont Fault Zone to test the ability in mapping complex active fault systems to depths up to 15km below the surface.
Three-dimensional modelling of this fault zone – developed from surface and sub-surface data – will ultimately show how faults rupturing at depth propagate to the surface over many earthquake cycles.
Earlier today a quake also struck in the lower North Island, this time a magnitude 3.6, which is predominantly being classed as weak by New Zealanders.
It comes after the region was rocked by a 4.7 magnitude earthquake at 10.56pm yesterday, which was felt by more than 10,000 people.
This morning's earthquake was located 35km northwest of Levin, at a depth of 26km, according to GeoNet.
About 180 people reported feeling the earthquake on the website; 140 reported weak shaking and 41 reported light shaking.