Tsunamis affect New Zealand's coastline reasonably frequently and tend to be caused by earthquakes on the Pacific plate both locally and as far away as South America, Japan, and Alaska. Some have been attributed to undersea landslides, volcanoes, and at least one meteor strike. New Zealand is affected by at least one tsunami with the a wave height greater than one metre every ten years on average.Willem de Lange and Eileen McSaveney. 'Tsunamis – Tsunamis – New Zealand's underrated hazard', Te Ara – the Encyclopedia of New Zealand, updated 13-Jul-12 The history of tsunamis is limited by the country's written history only dating from the early to mid-1800s with Māori oral traditions and paleotsunami research prior to that time. Studies are also being carried out into possible tsunamis on the larger inland lakes, particularly from landslides.Lake Tekapo chosen to probe risk to tsunamis on New Zealand lakes, One News, retrieved 30 March 2016

Significant tsunamis (greater than 1 metre)

New Zealand's proximity to the Pacific ring of fire means that it is subject tsunamis from numerous earthquakes. Those causing the largest impact on New Zealand tend to come from megaquakes in the Hikurangi Margin, a significant subduction zone.The clear and present danger of a devastating tsunami in Wellington, Charlie Mitchell05:00, Stuff.co.nz, 6 August 2022, retrieved 8 August 2022

Earthquake

880–800 yrs B.P. southern Hikurangi margin Research indicates a tsunami at least 3.3 metres high struck Big Lagoon, near Blenheim, 880–800 yrs Before Present from a megathrust earthquake on the southern Hikurangi Margin of the Pacific plate.

1820s Southland tsunami According to Māori history, several hundred Kāti Māmoe Māori were killed by a tsunami while walking along the beach near Orepuki in the 1820s. They had been gathering fish at the Waiau River mouth in autumn as provisions for the winter period. The beach runs between the sea and a line of cliffs meaning that only a moderate tsunami of 2–4 metres high would have been needed to cause so many deaths. The likely source of the tsunami could have been an earthquake on the Fiordland or Puysegur faults. There are questions around the exact date of this event as it is reliant entirely on unverified unnamed sources.EQC Project 03/490 – Understanding local source tsunami: 1820s Southland tsunami, G Downes et al, Institute of Geological & Nuclear Sciences client report 2005/153 – Project Number: 410W1034 and National Institute for Water and Atmospheric Research Consultancy report HAM2005-135 – Project Number: EQC04201, November 2005

1826 Fiordland earthquake and tsunami In 1826, sealers in Dusky Sound experienced a large earthquake that had aftershocks that went into the following year. The earthquake descriptions are considered consistent with a 7.6 to 8 magnitude quake given the extent of landslides and uplift. A tsunami or seiche caused by the uplift impacted the area where the sealers were. Its size has not been determined but it must have been significant (greater than 1 metre) to concern the sealers. They thought the small island on which they were residing was going to be swamped. There are questions around the accuracy of the year this event occurred. Given that the earthquake responsible for this tsunami was felt as being violent by the sealers, it is unlikely to be the same tsunami as in the previous section, since in the earlier event was not foreshadowed by noticeable ground shaking.

1855 West Wairarapa

The uplift from the earthquake on 23 January 1855 tilted the Wellington Region and with it Wellington Harbour. The eastern side of the harbour moved 80 centimetres higher than the western side displacing the water into the shoreline along Lambton Quay and flooding its houses and shops.Editorial, Taranaki Herald, volume=III, issue=133, 14 February 1855, Page 2

In Cook Strait, there was a much greater displacement. The Remutaka Range had risen about 6 metres and with it, the floor of the strait had been uplifted. The exact maximum height of the tsunami was not known but sheds at Te Kopi, South Wairarapa, which were 8 metres above sea level were destroyed.Editorial, Taranaki Herald, volume=III, issue=134, 21 February 1855, Page 3 The area impacted by the tsunami was as far north as Otaki and the upper South Island.The late earthquake, Nelson Examiner and New Zealand Chronicle| volume=712| issue=712, 21 February 1855, Page 2

About 20 minutes after the earthquake, a 3-4-metre high tsunami entered Wellington harbour through its narrow entrance and also across the Lyall Bay to Kilbirnie area.Editorial, Daily Southern Cross| volume=XII| issue=804, 13 March 1855, Page 2 The water was about 1 metre deep across the area. Captain Byron Drury, Commander of the sloop HMS Pandora reported:Earthquake at Wellington, Nelson Examiner and New Zealand Chronicle| volume=XIII| issue=705, 27 January 1855, Page 2 For eight hours subsequent to the first and great shock, the tide approached and receded from the shore every 20 minutes, rising from eight to ten feet and receding four feet lower than at spring tides. One ship, I heard, was aground at her anchorage four times. The action of the earthquake and its tsunami destroyed the bridge across the Hutt River.Wellington, Otago Witness| volume=06| issue=182, 17 February 1855, Page 3 Coasters entering Wellington harbour after the tsunami reported sailing through a large quantity of dead fish – principally ling.

1868 Chile

The 1868 Arica earthquake occurred on 13 August 1868, near Arica, then part of Peru, now part of Chile, at 21:30 UTC. The tsunami created by the quake reached New Zealand 15 hours later and caused substantial damage on the Chatham Islands and Banks Peninsula. It also affected many areas along New Zealand's eastern coastline from Great Barrier Island to Bluff.Earthquake wave in the sea, Lyttelton Times, volume XXX, issue 2387, 17 August 1868, Page 2The earthquakes and tidal phenomena, Daily Southern Cross, volume XXIV, issue 3467, 26 August 1868, Page 3 The tide at Wellington and Port Chalmers was reported as rising and falling by over a metre for a space of about 2 hours.Editorial, Star, issue 80, 15 August 1868, Page 2

The first area affected was the Chatham Islands, where the tsunami struck at about 1am (New Zealand time) on 15 August. News of the effect on the Chathams did not reach the mainland until 27 August, when the schooner Rifleman reached Port Chalmers. The Māori village of Tupuangi was totally destroyed, with only sand and seaweed marking its location. Fortunately, the first wave was small enough to awaken the sleeping villagers, enabling them to make it to safety. Subsequent waves carried out the destruction. Captain Anderson lost his house, which was about four miles from Tupuangi, but he and his family were able to reach safety. A Māori drowned while trying to save Captain Anderson's boat, which had come adrift. Thomas Hay, a sheep farmer, lost all he had. Buildings at Waitangi were damaged, including Beamish's accommodation house and the Government store.Arrival of the schooner Rifleman from the Chatham Islands, Otago Daily Times, issue 2048, 28 August 1868, Page 3

At about 4am, Mr Webb, a Canterbury railway night watchman at Lyttelton, noticed the barque John Knox was lying on her broadside and nearly touching the jetty she was discharging her cargo on. He woke her captain, Jenkins, who noticed that Lyttelton Harbour between the wharf and Officers Point was dry. Minutes later, there was a thundering noise from the direction of Officers Point, and they saw an enormous wave powering along the harbour. The power and ferocity of the wave snapped a number of boats warps, snapped the John Knox'''s mooring chain and drove her into the jetty, dragged the ketch Margaret into the harbour where she fouled the schooner Annie Brown, damaged the schooner Jeanie Duncan and the steamer Novelty. The tide kept rising and falling in the harbour for some hours after the initial wave.Extraordinary tidal wave, Star, issue 80, 15 August 1868, Page 3 The tsunami that entered the harbour has been estimated at 7 metres high but Captain Jenkins had referred to the wave as being 8 feet (2.5 metres) high when he saw it.

The bays around Banks Peninsula were also impacted by the tsunami, which penetrated far inland along valleys, damaging homes and carrying away bridges and fences. The ketch Georgina was wrecked at Rhodes Bay. At Pigeon Bay a succession of waves reaching up to two metres above the highest high water mark between 3am and 1pm carried away two jetties, 40,000 feet of sawn timber, a boat house, fencing, and the ketch Courier.Earthquake wave in the sea, Star, issue 81, 17 August 1868, Page 3

A 1.5-metre-high wave washed up the Waimakariri River at about 3am, snapping the stern line on the SS Gazelle, which caused her to swing around. The schooner Challenge broke away from her wharf and collided with the Gazelle. The William and Julia were lifted onto the riverbank and the Nora and Dart broke free from their wharf.

After the tsunami, Ferdinand von Hochstetter undertook a detailed analysis of the tsunami. He charted its progress across the Pacific Ocean, determining wave speeds and the ocean depth along several paths. It was the first detailed scientific analysis of a major tsunami. Julius von Haast, a friend of von Hochstetter and fellow geologist, writing to the Star two days after the tsunami reached New Zealand, pointed out that such waves travel at great speed and travel thousands of miles in a day.Julius von Haast. Untitled letter, Star, issue 81, 17 August 1868, Page 3

In 1912, the Evening Post carried a letter that suggested Westport had been submerged under a 10-metre-high wave, with the old township now lying metres under the sea. This story was later modified in the Colonist by its writer to being associated with the Arica earthquake with the sea at Westport receding some 7–8 metres and a returning wave of much less significance.The tidal wave of 1868, Nelson Evening Mail, volume XLVIII, 13 January 1914, Page 3Interesting reminiscences, Evening Post, volume LXXXIV, issue 37, 12 August 1912, Page 2 The original claims were repeated in a 2015 paper by Professor James Goff, of the University of New South Wales.West coast is tsunami 'blind spot' – new study, Ian Steward, Last updated 05:00, 23 March 2015 The Westport Times made no mention of the event in August 1868, other than the impact on other parts of New Zealand.

1868 east of New Zealand A few days after the Arica tidal wave arrived on 17 August 1868, there was a sharp earthquake, felt at both Nelson and Wellington at 9:57 and 9:56am respectively. Both harbours reported tidal waves with the one at Nelson over-topping the Boulder Bank. The wave was estimated to be just over a metre in height. The paper also reported that the tidal wave had impacted numerous South Island ports. The earthquake was felt at Christchurch at 10:01am.Earthquakes and tidal waves in New Zealand, Colonist| volume=XI| issue=1142, 4 September 1868, Page 3 Later reports indicated that the quake was felt almost simultaneously from Napier to Port Chalmers.Remarkable tidal waves, Nelson Examiner and New Zealand Chronicle| volume=XXVII, 5 September 1868, Page 2

1877 Iquique

On 10 May 1877 at 0:59 UTC, a magnitude 8.5 earthquake occurred near Iquique, Peru (now Chile). The resulting tsunami reached New Zealand's eastern coastline between 7 and 8am NZDT on 11 May. The wave had a reported 1–2-metre height in most places and impacted the coast from the Bay of Islands to Bluff. It also reached Westport on the West Coast at 2:30pm.(Per Press Agency)], Evening Post| volume=XV| issue=111, 12 May 1877, Page 2 At Akaroa and Gisborne the wave was in the 2–3-metre range. The waves at Port Charles on the Coromandel Peninsula were reported to be over 3 metres high.The tidal wave at Port Charles Auckland Star| volume=VIII| issue=2244, 16 May 1877, Page 2