Tsunami from South America
Posted 1 March 2010 // Simon Nathan
The impact of the 1868 Tsunami on Banks Peninsula
The tsunami alert resulting from the Chilean earthquake of 27 February 2010 is a reminder of the hazard that tsunamis pose to coastal areas around New Zealand.
In the early 21st century we have instant communication around the world. It was very different in August 1868, when one or more large earthquakes close to the Chile–Peru border caused a huge tsunami that spread around the Pacific Ocean. The first anyone in New Zealand knew was when the first wave arrived soon after 3 a.m. on 15 August. Sea-level fluctuations continued for over 12 hours, causing considerable damage, for example around Banks Peninsula.
James Hector, then in charge of the Geological Survey and the Colonial Museum, collected observations from around New Zealand. He wrote three separate reports, as more information came to hand.
On 25 August 1868 Hector was able to produce a graph of sea level changes from New Zealand ports, showing when the first wave arrived and how long the sea level continued to fluctuate. Although the cause of the sea level fluctuation was uncertain, in his first report Hector correctly deduced that it was probably caused by a distant earthquake.
By 1st September 1868 Hector had more information, including reports from the Chatham Islands, where one man was drowned trying to rescue a boat.
In his final report on 1st October 1868 Hector was able to confirm that the tsunami originated from South America, and also had compiled newspaper reports of the tsunami from around New Zealand and Australia.
The 1868 tsunami has considerable historic importance, as it was documented by Ferdinand von Hochstetter, an Austrian scientist who had visited New Zealand in 1859. He charted the progress of the tsunami across the Pacific. It is the first detailed scientific analysis of a major tsunami, but the results are not too different from what is being reported 140 years later.
Were you affected by the tsunami on Sunday?
It’s interesting to me that this big earthquake was at Concepcion, where Darwin also experienced a huge earthquake during his Beagle voyage. The land rose there several feet and Darwin used this as support for Lyell’s theories of land elevation and subsidence.
The sea-level rise in Australia was only 20 cm at the maximum this time. No damage. Some people were even a bit disappointed there was no more excitement!
David Oldroyd
I live in Cheltenham, midway between Waitemata Harbour and Cheltenham Beach, a few metres above sealevel. When I first heard a tsunami warning (c9.40am) I thought of photographs of the Indian Ocean tsunami, and decided that Cheltenham might not be safe. I immediately warned my neighbour to take her baby up Mount Victoria, and found that she was already preparing to do that.
I packed some food and drink plus a
portable radio (and a book), and reached the summit of Mt Victoria by 10.25, and was then joined by my neighbour with her baby. We admired the view and listened to the National Radio reports on the tsunami. We could not see any unusual waves, and at 11.30 we decided to return home.
On May 23 of 1960 I experienced (in a dinghy)in the Lyttelton Inner Harbour, the effects of the tsunami caused by the Great Valdivian earthquake in Chile. It was weird, without any sea surface effects I went down and then up several times. I understand that the maximum sea surface rise was 5M and some water slopped over the gate to the Graving Dock which had a ship under repair in it at the time. The behaviour of the public during this event in 1960 was EXACTLY the same as their reaction to the 2010 tsunami from Chile.
In 1958, I published a brief note drawing attention to European reports of a submarine volcanic eruption off East Cape, NZ, on 1 December 1877 (NZ Journal of Geology and Geophysics Vol. 1, No 3, pp 459-460). I attributed the reports to a tsunami resulting from an earthquake felt at Gisborne. Colin Laing, now living in Brisbane, had previously reported on tsunami resulting from earthquakes on the east coast of the North Island and other places (NZ Journal of Science and Technology, Vol B35, pp 470-472, 1954). I would be interested to know whether, after 50 years, my speculation is accepted that the 1877 event was a tsunami.
Don Gregg in Tasmania