article: Jan 1 2007 - Principal Earthquakes of New Zealand in 2006

A summary of New Zealand's earthquake activity in 2006.

Felt earthquakes in 2006. Green are likely to have been felt, yellow had the potential to cause contents damage, red had the potential to cause structural damage.

The year 2006 was a relatively quiet year for earthquakes in New Zealand, with a total of 26 events of magnitude 5.0 or greater. Of these, 17 occurred at depths greater than 100 km and the largest had a magnitude of 6.0. A total of 301 events, including four located outside the New Zealand region, were reported by the public as having been felt through the GeoNet website's questionnaire (www.geonet.org.nz).

The largest event occurred on the morning of February 16 and was centred offshore, 120 km north of Nelson. The magnitude 6.0 earthquake was at a depth of 180 km and was felt widely, from Hamilton to Christchurch, but because it was deep, the most serious damage reported was goods falling from shelves.

On August 13, the largest earthquake at a depth of less than 100 km occurred in the South Island, 30 km east of Murchison. With a depth of 95 km, the magnitude 5.9 event was reported felt from Auckland to Dunedin. Once again, because it was not shallow, there was no serious damage caused, although reports of goods falling from shelves were received from many localities.

The most widely felt earthquake for the year was actually centred beyond the New Zealand region, 800 km north-east of Auckland. It occurred on May 16 and was at a depth of 150 km with a magnitude of 7.6. Over 1500 felt reports were submitted for this event, which was felt widely from Auckland to Dunedin, and on the Chatham Islands. Reports of goods falling from shelves were received from many locations throughout the North Island.

A relatively shallow (47 km) magnitude 5.0 earthquake centred 40 km north-west of Wellington occurred on September 15. Because of its proximity to a major centre, close to 1400 reports were received. Goods off shelves were reported throughout the Wellington, Kapiti Coast and Marlborough regions. Another magnitude 5.0 event on May 15, at a depth of 60 km and centred 50 km north-west of Wellington, had a very similar pattern of felt responses, with nearly 800 reports received. On November 18, a magnitude 5.6 event at 70 km depth and centred 40 km north-west of Wellington was reported felt from the central North Island through to Christchurch. A total of 630 felt reports were received for this.

On July 8 the central Hawke's Bay region was shaken by a magnitude 5.4 earthquake centred 40 km north of Napier at a depth of 30 km. Close to 300 felt reports were received from throughout the central North Island. Three notable swarms of earthquakes occurred during the year. In the period from March 11 to 13, a sequence of eight events centred 30 km south-west of Wanganui, all at about 30 km depth and ranging in magnitude from 3.1 to 4.5, were reported felt. Five of these were over magnitude 4.0, and the largest was felt from New Plymouth to Wellington.

Over the period September 17 to 20, an unusual swarm of six small earthquakes were reported felt in the Bay of Islands area. These were centred close to Takou Bay at a depth of 5 km, with magnitudes ranging from 2.4 to 3.5. And on October 4, centred near Fox Glacier, a swarm of eight shallow earthquakes occurred over about three hours, the biggest having a magnitude of 4.6.