KEY POINTS:
Another quake like the one that rocked Auckland on Wednesday night is unlikely in the near future, say geologists.
The series of three tremors, the largest of which measured 4.5 on the Richter scale, was reported to be felt by residents as far north as Leigh, and as
far south as Waihi.
All three quakes were 30km east of Orewa in the Hauraki Gulf.
The Earthquake Commission has received 26 claims from Auckland homeowners so far, with more expected. Eleven were for homes in the Auckland city area, six were from the North Shore and four in Waitakere. The remainder were in the more outlying areas of the region.
Commission insurance manager Lance Dixon said most claims were for cosmetic damage such as cracks as a result of joints and plaster boards being jolted out of place.
"It's the sort of thing we'd [expect to] receive for an event of this size."
People have up to three months to lodge a claim, he said.
Bryan Field, duty seismologist at GNS Science, said the three earthquakes occurred in the same area as two tiny tremors recorded on January 30.
Because they were shallow, the earthquakes would have really shaken people up.
"The earthquakes, while not having a particularly large magnitude, were only 7km to 15km deep. This means they would have been felt intensely locally, with the potential to rattle and move a few small household items.
"You sometimes get earthquakes up to 300km deep, but definitely not under Auckland."
Quakes originating deeper in the Earth had lost much of their energy by the time they reached the surface, he said.
"It's kind of like being punched through a piece of paper, and being punched through a phone book. It just spreads out the shock a bit."
The quakes were not a portent.
"Our previous experience would suggest that they'll die down."
Nor were the quakes an indicator of possible volcanic activity, as they were well north of the Auckland volcanic field.
"Earthquakes happen from time to time and they can happen anywhere in the country. As to why it was centred off Orewa, there was obviously a knot of stress in the Earth's crust [as a result of two tectonic plates pushing together] and it got released as a series of small earthquakes."
More than 1500 people reported to the GeoNet website that they had felt the earthquake. They were far away as Waihi at the base of the Coromandel Peninsula.
Although Auckland is in one of the quietest parts of the country for earthquakes, small, mostly unnoticed earthquakes of less than magnitude 3 occur several times a year.
The last quake of note occurred on March 1, 1974, at 2am, when a magnitude 6.5 quake occurred 200km east of Auckland, in the sea off the Bay of Plenty.
The largest earthquake known to have affected the Auckland region was a magnitude 6 jolt centred near the mouth of the Waikato River on June 24, 1891. It brought down a chimney in Onehunga, but otherwise caused only minor damage.
During an earthquake
* Move no more than a few steps to a safe place, such as under a sturdy table or next to an interior wall.
* Drop, cover and hold on.
* Do not attempt to run outside.
* If outside, move no more than a few steps to a safe place, drop, cover, and hold.
* If in a lift, stop at the nearest floor and get out.
* If driving, pull over to the side of the road. Stay in the vehicle until the shaking stops.
* If near the coast, drop, cover and hold during an earthquake, and then move immediately to higher ground when the shaking stops.
* Expect aftershocks.
Source: Ministry of Civil Defence and Emergency Management
Watch the volcanoes, but don't forget those fault lines
An erupting volcano is considered Auckland's most likely natural catastrophe, but an active quake faultline, the Wairoa North Fault, runs to the south of the region into Clevedon.
Un-named inactive faults also exist in the Hauraki Gulf. The series of quakes on Wednesday night occurred immediately to the west of these faults.
GNS Science duty seismologist Bryan Field said the three quakes on Wednesday followed a build-up of pressure in the earth's crust caused by two tectonic plates pushing together.
"We live at the interface between two tectonic plates that runs right down the country, and earthquakes can happen anywhere," he said.
"There are areas where they are more frequent than others, like Wellington and Fiordland, but they can happen anywhere."
GNS Science geologist Steve Edbrooke said the faults in the gulf would create noticeable irregularities on the sea floor if they were active.
"You'd pick that up because a lot of survey work has been done on the seabed."
