Region rocking and rolling

In seismological terms, a moderate scale earthquake which rattled Waipukurau and was felt across a wide area of Hawke's Bay on Tuesday night was business as usual.

It was the third earthquake recorded in the Waipukurau region over the week - there were two "weak" shakes on July 20 and July 24 leading up to Tuesday's magnitude 4.3 shake which was recorded right on 8pm.

"It is not unusual and they do tend to happen in clusters and then, for a while, nothing," GeoNet seismologist John Ristau said. Which effectively meant there were likely to be more.

During the same period between July 19 and July 26, there were six earthquakes across the whole of the Bay and 24 across the whole country - the strongest being a magnitude 5 just northwest of Haast in the South Island which was also felt on Tuesday, just after 7.40am.

The other minor shakes were recorded 30km east of Napier, 10km south of Porangahau and 15km north of Pongaroa.

The latest Waipukurau shake resulted in 1297 "felt it" reports to GeoNet, although it was too small on the scale to cause damage.

Mr Ristau said the latest series of earthquakes reflected the fact that Hawke's Bay, as a whole, was one of the most seismically active regions in the country.

The latest earthquake centres were not on faultlines but were a result of the Pacific plate to the east pushing under the Australian plate to the west.

The earthquakes were occurring within the plates and were tagged as "slab" earthquakes.
While there was movement, the plates were effectively locked up and, at some stage, a more severe movement was likely to occur.

"It will happen," Mr Ristau said.

The theory that strings of small shakes took the pressure off was not entirely correct, he said.

"They will always move, regardless."

Tina Kennedy, owner-operator of Waipukurau New World Supermarket, said the shake was not enough to move anything, except the heart rate of her and her husband's dog.

"Oh, he knew; he started running around."

The earthquake lasted only a few seconds and was felt as a rolling motion.

A light earthquake was felt in Napier and Hastings at 1.15pm yesterday.

Geonet NZ reported the shake was magnitude 3.6 at a depth of 22km, 15km southwest of Hastings.