Earth Sciences NZ monitors cluster of earthquakes along eastern side of North Island

Earth Sciences New Zealand recorded 34 earthquakes this week 15km west of Castlepoint in the lower North Island. Photo / GeoNet

Seismologists at Earth Sciences New Zealand (formerly Niwa and GNS Science) have been monitoring a cluster of earthquakes off the country’s east coast.

The Government agency recorded 34 earthquakes this week 15km west of Castlepoint in the lower North Island.

Earth Sciences New Zealand seismic duty officer Sam Taylor-Offord said the largest was measured at magnitude 4.2 early Monday morning.

“This earthquake followed less than 10 minutes after a magnitude 4.1 in the same sequence,” he said.

“Of the 34 earthquakes, 31 have been less than magnitude 3. The sequence is playing out at around 20km depth.”

Taylor-Offord said more analysis was required to determine the specific drivers of the earthquakes.

“However, we can say the occurrence and behaviour of this sequence are normal for this area.”

Earth Sciences New Zealand recorded 34 earthquakes this week 15km west of Castlepoint in the lower North Island. Photo / GeoNet

He said the earthquake cluster was located in an area of subduction.

“An area where the Pacific Plate is actively subducting beneath the overlying Australian Plate.

“This collision and sliding loads stress into the plates and earthquake sequences like this are an expression of some of that stress being released,” Taylor-Offord said.

“Unfortunately, earthquakes like these aren’t releasing the stress of ‘the big one’. They are best thought of as a gentle – and sometimes not so gentle – reminder of the active tectonic environment we live in.”

A 4.7 earthquake rattled the Bay of Plenty in the North Island yesterday afternoon.

GeoNet registered the shake 25km north of Whakatāne at 4.56pm and at a depth of 127km.

According to GeoNet’s earthquake map, a flurry of quakes occurred east of Ruatōria on the North Island’s East Coast last week, with the strongest registered at 4.6 magnitude and a depth of 8km on Monday afternoon.

David Williams is an Auckland-based Multimedia Journalist who joined the Herald in 2023. He covers breaking news and general topics.