Chathams took brunt of tsunami

A massive earthquake off Peru

150 years ago ruptured

600 kilometres of seafloor, causing a tsunami that churned across the Pacific Ocean, crashing into the Chatham Islands and causing a 10 metrehigh wave that may have killed

20 people.

Thought to be the only deadly tsunami in New Zealand’s recorded history, the killer wave, which struck soon after midnight, is being marked at an event at the Chathams tomorrow.

A few hours after hitting the Chathams, the 1868 tsunami smashed into Banks Peninsula.

The following day, the sea rose and fell rapidly along the east coast from Mangonui in the north to Bluff in the south, and in a few places along the West Coast.

Known as the Arica Earthquake, the 1868 event is estimated to have had a magnitude of between 8.5 and 9.0. It killed an estimated 25,000 people in Chile and Peru, and took 15 hours to get to the Chathams, where there were three destructive waves.

At first there was a faint rumble, then a roar, which turned into water rushing up the beach and through the village of Tupuangi on Chatham Island’s northwest coast.

‘‘Ten minutes later a larger surge arrives, and after five minutes another. Whare, made of ponga, kopi/karaka and wood from old shipwrecks, are smashed to pieces, and dragged out to sea,’’ GNS Science science communicator Helen Jack said.

‘‘The land is stripped of trees and shrubs, and only sand, boulders and seaweed are left behind. Three families are washed away with their whare; those who survive scramble to higher ground and are left with nothing. Nearby, at Waitangi West, a man named Makere is drowned by an incoming wave while trying to save a whaling boat that had been washed along the coast.

‘‘There and elsewhere on the island, wooden houses, whare, sheds, stores, bridges and roads, some more than 10m above the high tide mark, are washed away or damaged,’’ Jack said.

Two hours later the sea rushed into homes on Banks Peninsula.

The third of three waves arriving 15 minutes apart was the largest and most violent.

The tide was half out in Lyttelton Harbour when the sea was suddenly sucked out of the port.

Then the nightwatchman heard an immense wave thundering up the harbour through the darkness. Boats were smashed as the water rose 5m in 20 minutes. A bridge 3km inland was destroyed.

GNS geologist and paleontologist Dr Hamish Campbell, who will be at the Chathams for the memorial event, said a similar event could strike at any time.

Nowadays, the sophisticated tsunami warning system in the Pacific would give New Zealand about 12 hours warning of a huge wave crossing the Pacific.

But there would be little warning of a tsunami generated by a rupture of the plate boundary close to New Zealand.