Even as many people along Hawaii’s coast rushed to higher ground, officials downgraded a tsunami warning to an advisory for southern Alaska and British Columbia. They also issued an advisory for areas of northern California and southern Oregon.
A small tsunami created by the magnitude 7.7 quake was barely noticeable in Craig, Alaska, where the first wave or surge was recorded Saturday night.
In Hawaii, Governor Neil Abercrombie proclaimed an emergency, mobilising extra safety measures.
Warning sirens blared while residents drove away from coasts and tourists were evacuated from lower floors of beachside hotels. Incoming bus routes were shut off into Waikiki and police shut down a Halloween block party in Honolulu.
The centre said the first tsunami wave could hit the islands by about 10:30 pm local time (0930 GMT).
At first, officials said the islands weren’t in any danger of a tsunami, but they later issued a warning, saying there had been a change in sea readings.
In Alaska, the wave or surge was recorded at 4 inches (100 millimetres), much smaller than forecast, said Jeremy Zidek, a spokesman for the Alaska Department of Homeland Security and Emergency Management.
The US Geological Survey said the 7.7-magnitude earthquake hit in the Queen Charlotte Islands area, followed by a 5.8-magnitude aftershock several minutes later. The quake was felt in Craig and other southeast Alaska communities, but Zidek said there were no immediate reports of damage.
The West Coast and Alaska Tsunami Warning Centre issued a warning for coastal areas of southeast Alaska, down the western Canadian coast to the tip of Vancouver Island.
Later Saturday evening, the warning for those areas was downgraded to an advisory, while a warning was issued for Hawaii. Early Sunday, the advisory was canceled entirely for Alaska.
Lucy Jones, a USGS seismologist, said the earthquake likely would not generate a large tsunami.
“This isn’t that big of an earthquake on tsunami scales,” she said. “The really big tsunamis are usually up in the high 8s and 9s.”
She said the earthquake occurred along a “fairly long” fault – “a plate 200 kilometers long” in a subduction zone, where one plate slips underneath another. Such quakes lift the sea floor and tend to cause tsunamis, she said.