Shaky Isles shown in new video

BY ANNA CHALMERS

New Zealand has been shaken by more than 16,000 earthquakes this year with a new video showing exactly where the country's hotspots are.

The video was information researcher Chris McDowall's first attempt at animating ten months worth of New Zealand earthquake data, which is collected by Geonet. It shows exactly where the 16,655 earthquakes occurred between March 1 to December 12.

Visualising New Zealand Earthquake Data from Chris McDowall on Vimeo.

Not surprisingly it showed Fiordland, where the world's second biggest quake so far this year occurred - the  Samoan quake measured magnitude 8, - was a major hotspot with a massive surge in July when the 7.8 earthquake and its aftershocks struck.

The North Island's central plateau, where there is considerable volcanic activity, along with the lower North Island off the Otaki coast and the Bay of Plenty's White Island, also featured highly for seismic activity this year.

Dr McDowall said most of the 16,655 earthquakes were tiny and would not have been felt. "They are not really quakes in a way. They're well under two [on the Richter Scale] and they are very small and very deep."

The Landcare Research employee said he was not an expert in earthquakes, but had an interest in opening such data-up to the public.

In Dr McDowall's video blue circles represent seismic activity, while each tremor leaves a small red dot to show the overall clusters of earthquakes. "The bigger the blue circles are, the bigger the quake."

Geonet duty seismologist Lara Bland said the video nicely illustrated where the country's faultlines sat with the areas of red dots, virtually mirroring tectonic plate boundaries.

Parts of the country with virtually no activity, including Northland and Otago, where not located near any major faultlines.

According to Geonet the Fiordland quake on July 15 was the biggest since the Buller and Hawke's Bay earthquakes of 1929 and 1931.

Despite its size there was little damage, which Geonet says relates to the quake's upwards rupture at a depth of about 30 kilometres. "The motion was more like a lurch than a snap." This meant the energy was released more slowly, creating lower frequency shaking and "rolling" rather than the sharp movements that cause building damage.

Ms Bland said aside from the Fiordland quake, 2009 had been a typical year for seismic activity and there appeared to be no more quakes than in other years.

- © Fairfax NZ News