Magnitude 8.1 quake near Kermadecs caused over 300 landslides on Raoul Island

March 26, 2021

The 8.1 earthquake near the Kermadec Islands on March 5 caused over 300 new landslides on Raoul Island, GeoNet and NZ Defence Force teams have discovered during flights over the island.

The quake struck at a depth of 28.9km near the Kermadec Islands, of which the unoccupied Raoul is the largest. It prompted a tsunami warning for parts of the North Island and caused small tsunami and surges.

Department of Conservation staff had manned Raoul Island up until March last year when they were being evacuated as New Zealand went into Covid-19 Alert Level 4. They have not returned since and it is under review whether they will return.

The ground shaking from the March 5 quake was estimated by ShakeMap NZ software to be between 0.15g and 0.75g.

Most of the landslides were relatively small, between 100 and 200 cubic metres of rock and soil avalanches and falls.

There were some larger ones up to about 20,000 cubic metres along the north-east coast near Hutchison Bluff, and around the crater of Blue Lake, approximately the areas of two rugby fields neck-deep, GeoNet said.

The most spectacular landslides were around the island’s Blue Lake, and along the coastline.

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