Story: Historic earthquakes
Page 5 – The 1929 Arthur’s Pass and Murchison earthquakes
Arthur’s Pass earthquake
At 10.50 p.m. on 9 March 1929 a magnitude 7.1 earthquake shook the mountain region near Arthur’s Pass for four minutes. Nearly continuous tremors followed for an hour, and aftershocks continued for days. Chimneys and water tanks collapsed, and rocks thundered down the nearby mountain slopes. Railway lines were damaged and slips closed the highway to the West Coast for several months. Despite the damage to houses, no one was injured. Two years later trampers discovered that a mountainside had collapsed during the earthquake, creating a huge landslide that swept 5 kilometres down the Otehake River. The earthquake is believed to have been caused by up to 4 metres of land movement along the Poulter Fault.
Shake, rattle and roll
Saturday night, 9 March 1929, found many people at a dance at the social hall in Arthur’s Pass. J. L. Spiers, a railway porter, commented: ‘The first indication of the shock was the middle of the roof descending about 18 inches, and the walls bulging out. Then the walls came in again and the floor went up and down.’ The lights went out, but there was no panic. When matches were struck, some of the people were found lying on the floor. 1
On 17 June 1929, at 10.17 a.m., a magnitude 7.8 earthquake struck the northern South Island. It was felt in cities and towns all over New Zealand. Nelson, Westport and Greymouth reported damage, but it was half a day before authorities realised that the worst hit region was Murchison.
For days preceding the earthquake, booming noises had been heard in the hills around Murchison. The earthquake itself was exceptionally noisy: rumblings were heard in New Plymouth, over 250 kilometres away. It was caused by movement along the White Creek Fault west of Murchison. Land moved upward as much as 4.5 metres along the fault.
When the main shock struck, wooden homes warped, twisted and shifted from their piles, and chimneys and water tanks collapsed. People scrambled outdoors, but once there found they were unable to stand.
A slip at school
Bob White, a pupil at Whale’s Flat school during the 1929 Murchison earthquake recalled:
‘We managed to get out near the gate and were thrown to the ground, which was rocking and heaving like a boat on huge waves by this time. After I suppose a minute … I saw a huge slip hurtling towards us. I yelled and we got to our feet and endeavoured to run back toward the building but the slip overtook us and went straight through the school, leaving the roof perched on top. We were saved by some poplars and a chestnut tree.’ 2
The shaking triggered dozens of huge slips on the steep mountain slopes, which were waterlogged from winter rain. Landslides blocked many rivers, including the Matiri, Maruia, Mōkihinui and Buller. The landslide dam on the Mōkihinui River later burst; the resulting flood seriously damaged Seddonville.
A massive landslide swept over the Busch and Morel homes, killing four people and damming the Mātakitaki River. In the Maruia valley a landslide pushed the Gibson home across a road and into a gorge, killing three people. Another swept the Holman home into the river, killing two. Of the 17 people who died in the earthquake, 14 were killed by landslides, and 2 in coal mine collapses.
With their homes uninhabitable and aftershocks continuing, residents camped in the open, or in sheds and tents. Communal kitchens were set up, but food supplies ran low. The landslide-dammed rivers posed a danger of flooding, so over several days most people left Murchison. They travelled part of the way in cars, then continued on foot, negotiating slips and streams. They eventually reached Glenhope, where they caught trains to Nelson.
Nelson, Greymouth and Westport had many damaged chimneys and brick buildings – the tower of Nelson Boys’ College collapsed, injuring two boys. In Karamea, damage was minor but numerous slips blocked the coastal road and food ran short. No outside help arrived until an aviator landed a Tiger Moth plane on the beach two weeks later. Vehicles could not reach the town for several months.
In 1936 the Danish seismologist Inge Lehmann used records taken from around the world of the Murchison earthquake to demonstrate that the earth has a solid inner core. It was an important breakthrough in understanding the nature of the earth's interior.
In an era when road work was carried out with pick and shovel, many roads buried by slips in the Buller region did not re-open for months. The Westport to Reefton road was closed for 18 months.