The South Island's 7.1 magnitude earthquake last week triggered more than 200 landslides in Fiordland National Park, geologists said today.
Staff from the Institute of Geological and Nuclear Sciences (GNS) have flown over about 70 per cent of central and western Fiordland since last Friday's quake, mapping its effects.
According to the United States Geological Survey website, the quake ranks as the fifth-equal biggest in the world this year.
"It is inevitable that an impressively big shake and steep country will combine to produce landsliding on a large scale," GNS spokesman Ian Turnbull said in a statement.
The landslide tally could exceed 220 as there were several valleys yet to be checked.
The most northerly slides found so far were on the Milford Track, 50km northeast of the quake's epicentre at Secretary Island, at the entrance to Doubtful Sound.
The most southerly landslide was at Breaksea Sound, about 25km south of the epicentre.
A landslide at the head of Lake Te Anau, about 65km from the epicentre, was the most distant from the epicentre, Dr Turnbull said.
The geologists had recorded at least seven major summit-to-valley floor slides covering vertical distances of up to 1500m.
They saw large numbers of trees and vegetation floating in the fiords, particularly Doubtful Sound, making a hazard for boating, and there was minor damage right around the shore of Lake Te Anau.
Landslides were a natural landscape-forming process that had been occurring in Fiordland for millions of years, Dr Turnbull said.
Information on them and the quake and aftershocks could help calculate which valleys, rivers and roads in the South Island had a high probability of being blocked when the Alpine Fault next ruptured.
The Alpine Fault runs almost the length of the South Island between Milford Sound and Marlborough. It ruptures every 250 to 300 years, producing an earthquake of about magnitude 8 and last ruptured in 1717.
GNS seismologist Warwick Smith is scheduled to speak on the Fiordland earthquake at a public meeting in Te Anau tomorrow.
The Earthquake Commission's insurance manager, Lance Dixon, will also attend the meeting organised by Southland District Council in response to requests from the public.
- NZPA
Quake triggers over 200 Fiordland landslides
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