The US West Coast and Alaska Tsunami Warning Centre said that any tsunami generated by the earthquake off the coast of Japan would hit Hawaii at around 2.45am (12.45pm GMT) and the US West Coast at 7.45am (3.45pm GMT).
Sky News US correspondent Robert Nisbet in the Hawaii resort of Wakiki said that some people were being told to move inland and others urged to move to the upper floor of buildings in case a tsunami hits.
"We understand that on Oahu there are 30,000 people in unsafe areas who are being told to move half a mile inland," he said.
"But what are talking about here in Wakiki is a vertical evacuation. There are a lot of skyscrapers here, a lot of hotels that sit along the Pacific coast. They are asking people who are below the third floor to move above the third floor and listen to the radio and TV for instructions.
"We have just been down to the shops ourselves to pick up some water and supplies and there are a lot of people down there."
Civil defence sirens were sounded statewide shortly before 10pm local time to alert residents. The tsunami warning said that all islands in the Hawaiian chain were in the path of potential damage.
Heavy traffic and long lines at petrol stations were reported on Oahu as residents tried to begin their journeys inland.
As residents prepared for the possible tsunami, a 4.5 magnitude quake hit Hawaii's Big Island, about 30 miles southeast of Hilo.
Indonesia, Australia, New Zealand and the entire Pacific coast of Central and South America were also on alert. Tsunami waves were due to make landfall at the following times:
:: 9am - Northern Mariana Islands - no large waves hit
:: 9.17am - Guam - initially appears unaffected
:: 10.02am - Philippines
:: 11:32am - Papua New Guinea
:: 11.35am - Indonesia
:: 1.10pm - Hawaii
:: 2.16pm - Vanuatu
:: 2.53 - Samoa
:: 3.35pm - Australia
:: 4.12pm - US west coast
:: 5.23pm - New Zealand
:: 11.00pm - Easter Island
Oceanographer Dr Simon Boxhall said: "The fact that a 10m wave has hit Japan implies that there is the scope for a wave to go right across the Pacific.
"The wave moves very quickly - it moves in the deep ocean at about the speed of a jumbo jet. The advantage is that we get plenty of warning as you head further away from the epicentre," he said.
"When we had a similar earthquake off the Chilean coast last year they tracked that tsunami for about 12 hours in total. It caused a lot damage around Chile but had largely fizzled out before Hawaii.
"But in this case you never know. It is happening in relatively deep water, it's propagating out across an open Pacific and so there is potential for damage to be caused all around the Pacific coast."
The Red Cross has warned that the tsunami waves could wash right over some Pacific islands as the wave is curently higher than some of them.
"Our biggest concern is the Asia and Pacific region, where developing countries are far more vulnerable to this type of unfolding disaster. The tsunami is a major threat," spokesman Paul Conneally said.
Ocean waves up to two metres above normal sea level were detected by deep-ocean gauges near Wake island, Midway and Guam in the North Pacific, the Pacific Tsunami Warning Center said.
Residents of the US territory of Guam were urged to move at least 15m above sea level and 30m inland.
Disaster management expert Geoff Williams: "The key thing in these areas that could be affected is that the companies like petrochemical companies, electric companies, will be assessing if they should shut down.
"Equally, old folks' homes, hospitals, schools they can start to make sure these are closed and they can start evacuating areas."
Taiwan's central weather bureau said minor tsunamis had reached the island's coastline without causing any damage.
Russian authorities on the far eastern Sakhalin Island and nearby territories have evacuated some 11,000 residents from coastal areas in anticipation that tsunami waves could hit several villages.
Residents on the eastern coast of the Philippines were also ordered to leave their homes.