Landslides triggered around the crater rim of Blue Lake on Raoul Island.
The March 5 magnitude 8.1 earthquake in the Kermadec Islands triggered more than 300 landslides on the steep forested slopes and rugged coastal cliffs of Raoul Island, GeoNet says.
The most spectacular landslides were around Blue Lake, and along the rugged coastline. There was a significant slip at Bells Beach, where about 400 metres of coastal cliffs collapsed, leaving a plume of sediment in the ocean.
Most of the landslides were relatively small rock and soil avalanches and falls of about 100-200 cubic metres, but there were some larger ones up to about 20,000m³ – about two rugby fields neck-deep in rocks, GeoNet said.
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Coastal landslides and rockfalls near Ngaio Bluff on Raoul Island, with Blue Lake in the background
As predicted by a tool for forecasting earthquake-induced landslides, most of the landslides were on coastal coasts, while some of the larger landslides were on the volcanic crater rim.
ShakeMap NZ software estimated ground shaking from the earthquake to be between 0.15g and 0.75g, GeoNet said.
GEONET/NZDF
Cliff collapse along Bells Beach, on the north coast of Raoul Island
The landslides were mapped using photos taken by GeoNet and NZ Defence Force teams who visited Raoul Island after the earthquake, and by using an image taken by the Pleiades satellite.
GNS Science staff went ashore on Raoul Island to restore a data communications link that was lost during March 5 event.
The major earthquake activity started with a 7.3 magnitude event off East Cape about 2.30am. That was followed by a 7.4 magnitude quake under the seabed near Raoul Island about 6.40am.
GEONET/NZDF
A closer look at the Blue Lake landslides
Then about 8.30am there was an 8.1 magnitude earthquake, also near Raoul Island, which is the largest and most northernmost of the main Kermadec Islands.
GNS, MetService and the Department of Conservation all have facilities on Raoul Island. After the earthquakes, the Navy ship Canterbury headed to the island, which is about 1000km north-northeast of New Zealand, with small teams from GNS and MetService on board.
DOC said there was no significant damage to its buildings on the island.
Source: Stuff New Zealand
