2013 Cook Strait and Lake Grassmere earthquakes
At 5.09 p.m. on Sunday 21 July 2013, a magnitude 6.5 earthquake rocked central New Zealand, causing minor damage. The earthquake was centred in Cook Strait, about 20 kilometres east of Seddon. In Wellington, plate glass fell from some downtown buildings. The following day much of the central city was closed for business as buildings were assessed for structural damage.
The period of seismic activity continued with a 6.6 magnitude quake at 2.31 p.m. on Friday 16 August. Centred near Lake Grassmere, the quake damaged buildings in Seddon and nearby towns and some buildings in Wellington.
2016 Kaikōura earthquake
At 12.02 a.m. on Monday 14 November 2016, a magnitude 7.8 earthquake, the second strongest quake since European settlement, shook the eastern coast of the northern South Island. Lasting for nearly two minutes, the complex earthquake started near Culverden, then moved north-east, jumping between at least 21 faults, both onshore and offshore, along 180 kilometres of the Marlborough coast.
The shaking brought down tens of thousands of landslides from the mountains. Two people died, one in the collapse of a homestead near Kaikōura and one from a head injury.
Damage to urban areas
Blenheim, Ward, Kaikōura, Waiau, Hanmer Springs, Cheviot, Culverden and other small towns in the region had substantial damage.
Strong shaking in the Wellington area damaged port facilities and many office buildings. Thousands of workers had to work from home or relocate to new offices as damaged buildings were inspected, and either demolished or closed for repairs.
Landslides and damage to roads and railways
Between 80,000 and 100,000 landslides were triggered by the earthquake and aftershocks, burying sections of State Highway 1 and the main trunk railway line and isolating the town of Kaikōura. Some landslides blocked rivers and streams, creating about 200 landslide-dammed lakes. The earthquake damage disrupted overland transport between Picton and Christchurch, halting train travel and necessitating detours of nearly 140 kilometres for road traffic.
More than 600 tourists were stranded at Kaikōura. Some 450 were evacuated to Lyttelton aboard HMNZS Canterbury and 165 on New Zealand Defence Force helicopters. The military also delivered food, water and other supplies to the town. State Highway 1 reopened between Kaikōura and Christchurch in December 2016, and between Kaikōura and Blenheim a year later.
A changed coast
During the Kaikōura earthquake, large areas of the South Island’s northeastern coast shifted upward and northward. Cape Campbell moved 5 metres closer to the North Island. The greatest amount of uplift measured was 8 metres, while the largest horizontal movement was 12 metres.
The Marlborough coast generally was raised between 0.5 and 2 metres from about 20 kilometres south of Kaikōura to Cape Campbell. Uplift of large swaths of the seabed left marine life such as pāua and crayfish exposed.
Several submarine faults ruptured, triggering minor tsunami. Hundreds of people moved to higher ground in Kaikōura and cities such as Wellington and Christchurch.
Because of uplift of long stretches of the coast and the fact that it was low tide in the area, the effects were minor. The maximum tsunami height, 6–7 metres, was at Goose Bay, with 2.5-metre waves at Kaikōura and 1.6 metres at Wellington. At Little Pigeon Bay on Banks Peninsula, a 3-metre wave pushed a holiday house off its foundations.