Jan 1 2009 - Principal earthquakes of New Zealand in 2008

Felt earthquakes in 2008.

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

The most destructive earthquake in 2008 occurred on the night of August 25 and was centred 10 km south-west of Hastings at a depth of 30 km. The magnitude 5.9 earthquake was widely felt from Waikato to the upper South Island, with close to 1,300 reports submitted on the GeoNet felt earthquake reporting system. The region around Hastings and Napier reported damaged chimneys, broken windows and cracked walls. The falling of items from shelves was widespread, and an office building in Taradale was deemed unsafe for a short time. It was the most damaging earthquake in Hawke’s Bay since 1990. The aftershock activity was light, which is usual for earthquakes at this depth and located within the subducted Pacific plate.

The largest earthquake in the New Zealand region was of magnitude 6.0. It occurred on July 12 and was centred in south-west Fiordland. Because it was at a depth of just over 100 km and located in a sparsely populated area, damage reported was limited to a few instances of items falling from shelves in Central Otago and Southland. On January 21, a shallow earthquake of magnitude 5.5 in the same region produced a similar felt pattern, apart from an isolated report of cracked walls and toppled furniture in Te Anau.

In September two moderately-sized earthquakes, both at depths of about 90 km, were felt widely in the North Island. The first, a magnitude 5.8 on September 1, was centred 50 km south of Taupo. It was felt mainly from the Bay of Plenty to Marlborough and most strongly in Hawke’s Bay and Manawatu, where there were reports of items falling from shelves. On September 14, a magnitude 5.1 earthquake centred offshore, 60 km south-west of Wanganui, was felt mainly throughout the western side of the North Island and in Nelson and Marlborough. Over 1,600 reports were received, the most for any earthquake in 2008, with several of those from south-west coastal North Island regions and Marlborough reporting items falling from shelves.

On September 25 and 26 the northern South Island was shaken by two earthquakes of magnitudes 5.1 and 5.2 centred about 20 km north-west of Kaikoura. Both were felt widely from Wellington to Christchurch, with minor damage reported around Kaikoura. And on December 18, a magnitude 4.9 earthquake centred close to Hanmer Springs was felt throughout the upper South Island.

The most widely felt deep earthquake occurred on December 19 and was located 20 km south-west of Rotorua at a depth of 180 km with a magnitude of 5.8. It was felt mainly throughout the eastern side of the North Island.

Throughout the year a total of seven earthquakes located outside the New Zealand region were felt. The most widely felt of these occurred on March 28 and was a magnitude 6.2 event centred about 650 km north-east of Auckland at a depth of 400 km. This was felt in the Bay of Plenty and along the east coast of the North Island.

Seismic swarm activity near Matata in the central Bay of Plenty, which began in January 2005, continued at a reduced level in 2008 with a total of 60 felt earthquakes throughout the year. The two biggest of these, one on January 24 and the other on November 2, had magnitudes of 4.3 and were felt widely throughout the Bay of Plenty. The busiest month for this activity was January, during which 17 of these events were felt. The area continues to be monitored closely, and about 1,000 events were located in the region in 2008.

The last widely felt earthquake for the year was on December 27 and centred in the Wanganui Basin, 30 km offshore from Otaki, at a depth of 50 km and with a magnitude of 5.1. It was felt mainly around the south-west coast of the North Island and in Nelson and Marlborough. The only damage reported was a few instances of items falling from shelves.