Tsunami

Wairarapa earthquake tsunamis, 1855
On 23 January 1855, a magnitude 8.1–8.2 earthquake, the most powerful to strike New Zealand since European settlement, shook the lower North Island. It generated not one, but several types of tsunami.

During the earthquake, the entire region west of the Wairarapa fault lurched abruptly north-east. Like soup in a bowl that is jostled, the water of Wellington Harbour slopped onto the adjacent land. The next movement of water occurred because the entire Wellington region had tilted – the eastern side of the harbour was now about 80 centimetres higher than the western side. The harbour waters ponderously moved off downhill, towards central Wellington. Houses and shops were flooded along Lambton Quay, which at that time was along the shore.
The greatest tsunami, however, was generated in Cook Strait. The Rimutaka Range rose as much as 6 metres, and part of the floor of the strait was probably uplifted. The tsunami destroyed sheds more than 8 metres above the sea at Te Kopi, on the southern Wairarapa coast. It moved along the strait and up the Kapiti coast – stranding fish as far north as Ōtaki – and spread across to the South Island.
Many turns of the tide
The sloop Pandora was anchored in Wellington Harbour at the time of the 1855 earthquake. Her commander, Byron Drury, reported: ‘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.
About 20 minutes after the earthquake, tsunami waves surged into Wellington Harbour through its narrow entrance, then for many hours bounced repeatedly back and forth, reflected off the harbour sides. Water also flooded into Lyall Bay from Cook Strait and Evans Bay from Wellington Harbour, putting the low isthmus between them (the site of Wellington Airport) under nearly a metre of water.