Hauraki Gulf Earthquakes Shake Up Aucklanders

NEWS RELEASE from GNS Science
22 February 2007
Hauraki Gulf Earthquakes Shake Up Aucklanders

Aucklanders were shaken by three tremors last night. The largest of these was a magnitude 4.5 earthquake that struck at 9pm, and was felt from Warkworth in the north right through to Waihi at the base of Coromandel Peninsula.

No reports of damage have been received, apart from minor issues such as a few items falling from shelves. The two smaller earthquakes occurred at 8:24pm and 11:23pm, and were of magnitude 3.7 and 3.8 respectively. All three quakes were centred 30km east of Orewa.

GNS Science Duty Officer Bryan Field said that due to their shallow depth, the earthquakes would have really shaken people up.

“The earthquakes, while not having a particularly large magnitude, were only seven to fifteen kilometres deep. This means they would’ve been felt intensely locally, with the potential to rattle and move a few small household items. Their size would’ve been too small to do more than give people a nasty fright,” Mr Field said.

It is unusual for Auckland to experience this level of earthquake shaking. The last time this occurred was on March 1, 1974 at 2am, when an earthquake of magnitude 6.5 occurred 200km east of Auckland, well out to sea in 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 to fragile items and plasterwork.

Last night’s earthquakes occurred in the same area as two tiny tremors on January 30, 2007. All of these have been well north of the Auckland volcanic field and are not indicators of possible volcanism. Due to their infrequent nature, the shakes have generated huge public interest in the Auckland region.

More than 1400 public responses were received through the GeoNet web site www.geonet.org.nz, as people described their experiences of the quakes. The results of these questionnaires enable scientists to better understand how future earthquakes may affect people.

ENDS

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