Experts believe quakes will ease

Senior Emergency Management Officer Shane Briggs monitors seismic activity around Taranaki.
Senior Emergency Management Officer Shane Briggs monitors seismic activity around Taranaki.

As the land in Taranaki continues to shake, so too are many of its residents.

Sunday evening's 3.0 magnitude earthquake five kilometres southwest of New Plymouth, followed by a 2.4 magnitude quake, took the region's total to 18 since a big jolt early on January 1.

An online poll run by the Taranaki Daily News yesterday suggested the constant shaking was of concern to slightly more than half the voters.

Of the 466 who voted, 51 per cent said they were "scared" or "a little bit jittery" about the quakes.

The remainder of people who voted had either not felt the earthquakes, or were not scared.

However, scientists have said there is nothing to worry about.

The majority of the quakes, including the severe 5.0 magnitude on January 1, have occurred off the Opunake coast.

GNS Science vulcanologist Steve Sherburn said while he initially thought the quakes would die down days after the January 1 event, he was not surprised they had continued.

"What we sometimes see are things called earthquake swarms.

"They're most common in the volcanic region in the central North Island, but they do also occur in the Cape Egmont fault zone." Mr Sherburn said that historically, the Cape Egmont fault did not produce large earthquakes, however, about 100 to 200 occurred in the area each year.

"Faults in Taranaki do have the potential to produce larger earthquakes, but in terms of their ranking in the country, they're not near the top.

"Then again, we know Christchurch wasn't near the top either," he said.

However, the most powerful earthquake felt in New Zealand last year was a magnitude 7 quake on July 3, about 60km south of Opunake at a depth of 230km.

It was felt from Northland to Southland and caused minor damage in Whanganui, on the Kapiti Coast and in Lower Hutt.

While question marks hang over the process of fracking and its possible impact on seismic activity, a report prepared by GNS last year showed no evidence that hydraulic fracturing in Taranaki between 2000 and 2011 had triggered earthquake activity.

The report also showed there were no fracking locations west of Mt Taranaki, where the Cape Egmont fault zone lies.

In the July 2011 to June 2012 period, there were 276 recorded earthquakes in the region.

That included a small cluster near Pukeiti and several earthquakes beneath the western and southwestern parts of Mt Taranaki.

All earthquakes near the mountain were deemed insignificant to the mountain's volcanic activity, which was also the case with the recent shakes, Mr Sherburn said.

"We don't see many earthquakes under the mountain.

"There are some, but any that we do see don't seem to be linked in any way to things out near Opunake at all," he said.

The offshore fault zone did not run near Mt Taranaki and while it was an obvious question to ask, Mr Sherburn said volcanic activity had not increased.

"Based on what we see fairly regularly, I don't think there's any reason for people to be concerned.

"If you look at the past 10 or 20 years, what we've seen in the last two weeks isn't unusual, but it certainly doesn't happen every year."

Comments written on Taranaki Daily News' Facebook page yesterday differed between those who were troubled by the recent shakes and those who were unconcerned.

One person wrote: "It has me on edge every time I hear a rumble starting", while another said: "Maybe Taranaki will break away from the rest of New Zealand and become an island on its own".

Another comment said: "Not concerned at all. After a stint down in CHCH the ones here are nothing."

Civil Defence senior emergency management officer Shane Briggs said while the recent quakes were of no major concern, it was a good reminder that people needed to be prepared.

"It's a reminder that events of any size can happen at any time throughout New Zealand," he said.

"As GNS has said, these ones are related to January 1.

"They're not under the mountain and we're not worried about an eruption which is often people's immediate concern."

Mr Briggs said GNS would continue to monitor the mountain and if any pivotal or unexpected trends came about, people would be notified.

"At this point in time it's just doing what we would expect after that 5.0 magnitude quake," he said.

Taranaki Daily News