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The only warning the Samoan people would have had of yesterday's tsunami was the earthquake that struck just a few minutes before.
Despite a forewarned New Zealand having the luxury of a few hours to prepare for what eventually was little more than a ripple around coastlines here, the warning systems meant little with a locally-generated tsunami.
"What you can't do anything for by way of a warning system is a locally-generated tsunami and the earthquake itself has to be the warning ... for many people in Samoa it was," said GNS senior seismologist Warwick Smith.
Tsunamis, which are barely noticeable out at sea, can travel at speeds of up to 600km/h depending on water depth.
This would have left the people in Apia, which was 205km from the epicentre of yesterday's 8.3 earthquake, about 20 minutes to ready themselves for the disaster.
Unlike a normal wave, the driving energy of a tsunami moves through the water as opposed to on top of it and is barely noticeable above the waterline.
A tsunami is typically no more than a metre high until it gets close to shore
"In deep oceans they travel at something like 600km/h ... it's not like a wave at that speed it's just like a gradual raising of the ocean surface," said Mr Smith.
"If you think of a wave coming into shallowing water the front starts travelling slower while the back starts travelling fast so it bunches up and builds in height, this is where the real problems start."
Mr Smith said the Pacific Tsunami Warning Centre in Hawaii would have alerted Civil Defence that a large earthquake had occurred under the ocean.
He said computer models predicting arrival times for tsunamis were based on the fastest possible track for tsunami waves
"But, in fact, most of the energy that produces the biggest waves may not go along the track and may come in a bit later - at Raoul Island I think it was an hour later they got the first significant waves in there."
Volcano geophysicist Steve Sherburn said only large earthquakes were likely to displace the seafloor causing an imbalance in the water resulting in a powerful wave rushing in all directions.
"If there was an earthquake 200km down there wouldn't be a tsunami," he said.
"But this was something like 30km down so it was close enough to the surface for the sea floor to move."
- ADDITIONAL REPORTING: AGENCIES
How you can help
Pacific Cooperation Foundation
Deposits can be made at at any Westpac branch. All the money raised will go to the Samoan Government
Red Cross
- Make a secure online donation at www.redcross.org.nz
- Send cheques to the Samoan Red Cross Fund, PO Box 12140, Thorndon, Wellington 6144
- Call 0900 31 100 to make an automatic $20 donation
- Make a donation at any NZ Red Cross office
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