NEWS RELEASE from GNS Science
JANUARY 1 2006,
MORE THAN A QUAKE A DAY MAKES 2005 AVERAGE-SEISMOLOGISTS SAY
Seismologists today described 2005 as an average year for earthquakes in New Zealand, with two quakes bigger than magnitude 6.0, and 24 between magnitude 5.0 and 5.9.
The public reported 390 quakes through the GeoNet website during 2005. This is about 2 percent of the total number of quakes recorded during the year by the GeoNet national network of instruments. The majority were either too small or too deep to be felt.
The most damaging quake of 2005 occurred on the morning of January 21 and was centred just north of Upper Hutt. The magnitude 5.5 quake had a depth of 32km and was felt between New Plymouth and Christchurch. It produced 1077 property damage claims, resulting in a cost of $2.13 million to the Earthquake Commission.
The year's biggest quake was a magnitude 6.4 on March 14 centred 80km south of Opunake at a depth of 154km.
It was felt widely between Auckland and Christchurch, but was too deep to cause any serious damage.
Three notable swarms of earthquakes occurred during the year. The longest-running swarm at Matata in Bay of Plenty started in early February and lasted for much of the year. It consisted of several hundred quakes, some of which were felt widely in Bay of Plenty. They were all at a depth of 5km with the largest a magnitude 4.1 quake on June 13.
There were shorter-lived swarms at Te Aroha and Seddon in Marlborough. The biggest quake in the Seddon swarm, a magnitude 4.8 event in early November, caused some property damage in Marlborough.
A cluster of six small quakes under Waiheke Island, east of Auckland, in late November startled some island residents, but there was no damage. Earthquakes in the Auckland region are rare, and six in one day is even more unusual. Seismologists attributed the quakes to the release of tension in the earth's crust.