In the early morning of 1 September 1888, an earthquake with an estimated magnitude of 7.0–7.3 struck the Amuri district of North Canterbury, about 100 kilometres north-west of Christchurch. Felt from New Plymouth to Invercargill, the quake caused damage to buildings over a wide area, including Christchurch.
Although many major earthquakes have struck without warning, this one was heralded by three weeks of noisy foreshocks, which people in Amuri heard as distant rumblings. On 30 August tremors were felt in the Hope Valley from 6.20 p.m. onward, gaining in intensity until an earthquake at 10 p.m. stopped clocks and rang church bells in Canterbury and Westland. More tremors followed the next day. In the late evening they increased in strength and frequency, growing louder until they became deafening before the main earthquake struck at 4.10 a.m. on 1 September.
The heavy shaking lasted 40 to 50 seconds in Christchurch, and there were many aftershocks, several of them felt in Christchurch in the first quarter-hour after the main quake. Aftershocks continued beneath the Hanmer Plains for more than a month.
In North Canterbury, especially in the Hope valley and Hanmer areas, many farm buildings were badly damaged or destroyed, including cob structures (made of rammed earth) and brick and stone buildings. Wooden buildings shifted off their foundations or were badly warped. The earthquake caused landslides in loose sediment, and fissures up to 30 centimetres wide appeared along terraces of the Percival River and in the Hanmer Plains.
In Christchurch, the most notable damage was to Christchurch Cathedral. The top 7.8 metres of the stone spire collapsed, in part because of the sway of the heavy iron cross secured to its top. The Durham Street Wesleyan Church lost some stonework, and the Normal School in Cranmer Square had cracked ceilings and damaged chimneys. Many homes also had broken chimneys and windows. There was more damage in the northern and north-western suburbs, probably due to the peaty subsoils underlying the buildings there. At Lyttelton, boats swung at their moorings, and 10-ton blocks of rock tumbled from bluffs along the Sumner road.
Lamenting a landmark
This report appeared in the Lyttelton Times on 5 September 1888:
‘[T]he spire of the Cathedral has come to grief. Its tapering, graceful outline, a landmark for every dweller on the plains within thirty miles, and a beacon for the mariner crossing Pegasus Bay, no longer cuts the sky. Twenty-six feet of the upper spire have given way, and the melancholy appearance of the wreck strikes every eye.’
Strong shaking was reported from the Ōtira Gorge, where new hot springs were observed. Households in Hokitika and Greymouth had damaged chimneys and broken crockery.
The earthquakes were caused by movement along a 30-kilometre section of the Hope Fault, from the junction of the Hope and Boyle valleys to the Hanmer Plain. This major fault crosses the South Island from the Alpine Fault at the Taramakau River to the coast north of Kaikōura. In the Hope valley west of the Hanmer basin, geologist Alexander McKay discovered that farm fences had been offset horizontally by 1.5 to 2.6 metres along the fault. He was the first in the world to show that horizontal movement could occur along faults during earthquakes.