The first waves of the tsunami triggered by the earthquake in Chile have hit New Zealand's eastern Chatham Islands and officials have warned bigger waves are to follow.
"It is expected that the greatest wave heights will occur between six and 12 hours after the initial arrivals," the Ministry of Civil Defence and Emergency Management said in a statement.
Residents on the Chatham Islands were moved to higher ground several hours before the first wave struck and residents in low-lying areas of Banks Peninsula had been told to be prepared to evacuate.
The biggest tsunami warning in history was marked by alarm sirens, panic buying and mass evacuations across the Pacific, eastern Asia, Australia and New Zealand.
The Chilean earthquake triggered a tsunami that radiated across the Pacific basin and swamped the island chain that inspired the story of Robinson Crusoe.
The warnings came barely five years after the 2004 Asian tsunami sparked by an underwater quake off Indonesia inundated coastal communities with waves up to 100 ft high, claiming an estimated 230,000 lives.
Chile's Juan Fernandez islands, about 400 miles off the coast, were the first to feel the full force of the tsunami and "serious damage" was reported.
The chain includes Robinson Crusoe island, named after Daniel Defoe's protagonist, and another named after Alexander Selkirk, the Scottish sailor on whose real life experiences the novel is said to be based.
Michelle Bachelet, the Chilean President, said an evacuation of coastal areas on Easter Island, the Chilean territory famous for its monumental statues, was launched as the tsunami approached.
Unlike during the devastating Dec 2004 tsunami, emergency officials across much of the Pacific had several hours to prepare for the impact and arrange evacuations.
"We've got a lot of things going for us," said Charles McCreery, director of the Pacific Tsunami Warning Centre (PTWC) in Hawaii. "We have a reasonable lead time. We should be able to alert everyone in harm's way to move out of evacuation zones."
In Hawaii, supermarkets were packed during pre-dawn hours as people stripped the shelves of bottled water, basic foodstuffs and other essentials such as water. Cars lined up 15 deep at petrol stations.
Locals and tourists began to evacuate beachfront communities and hotels as the first warning sirens were sounded at 6am local time, five hours before waves of up to six feet were expected to hit.
Boaters at the quay in Honolulu loaded up with supplies and sailed their vessels offshore where they would be better able to ride out the waves rather than risk being battered at shore.
Nervous cruise ship passengers were also assured that while tsunamis can turn into colossal waves near land, their impact out at sea is limited.
The PTWC issued a tsunami warning, its highest alert, for the entire Pacific region, including countries as far away as Russia and Japan.
California and Alaska were issued a separate tsunami advisory.
New Zealand also issued a tsunami alert, warning of a wall of water up to 10 feet high. The National Crisis Management Centre warning said the greatest wave heights were expected between six and 12 hours after the initial arrivals.
Waves up to six ft high struck parts of French Polynesia and residents were warned to remain vigilant as tsunamis can consist of several surges and the first is usually not the strongest.
Several Chilean coastal towns were pounded by waves up to nine feet high during a holiday weekend when many people are on holiday at the beach for the official end of summer.
Residents and tourists on Ecuador's Galapagos archipelago - where Charles Darwin conducted research that led to his theory of evolution - were moved to high ground before unusually strong waves struck the shore.
Dr Brian Baptie, British Geological Survey's Head of Seismology, explained why most of the Pacific region would have time to prepare. "Tsunami waves in the deep ocean travel at about the same speed as a jet plane and would take about 15 hours to reach Hawaii and about 20 hours to reach the other side of the Pacific," he said.
Dr David Rothery of the Department of Earth and Environmental Sciences at the Open University, said: "A magnitude 8 quake is a rare event. On average there is only about one of these per year, globally. This one was caused by the floor of the Pacific Ocean being pushed below South America. Because the epicentre was under the sea, the sudden jerking of the sea-floor displaced water and triggered a tsumani."
Additional reporting by Fiona Govan in Madrid and David Barrett in London