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 addition, officials issued an advisory for areas from Gualala Point, Calif., about 80 miles northwest of San Francisco, to the Douglas-Lane county line in Oregon, about 10 miles southwest of Florence.
The U.S. Coast Guard in Alaska said it was warning warn everyone with a boat on the water to prepare for a potential tsunami.
A tsunami warning means an area is likely to be hit by a wave, while an advisory means an area could be hit.
The first wave hit Craig about two hours after the earthquake.
“It started off where it might be a 3-foot wave, and it kept getting downgraded,” Craig Mayor Dennis Watson said. “And the last time we heard, it was less than 1 foot.”
It actually was recorded at 4 inches. Watson said he was downtown on the waterfront, and had his car lights shining on pylons.
“I didn’t even see the surge. I watched the pylons. And the tides came in about four or five inches. The surge would leave a wet spot as it would go back out, and we never did see that,” he said.
There could be subsequent waves in Craig, but an official with the tsunami warning center didn’t think it would amount to much.
The first wave “typically is not the largest but nevertheless we don’t expect the maximum wave height to be large,” said Bill Knight.
The state Department of Homeland Security and Emergency Management activated its emergency operations center and notified officials in southeast Alaska communities.
Lt. Bernard Auth of the Juneau Command Center said the Coast Guard was also working with local authorities to alert people in coastal towns to take precautions.
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.
In Craig, officials implement an emergency plan, and took fire trucks, ambulances and heavy equipment to higher ground.
“If nothing else it was a good exercise in determining how well our disaster plan works. I thought it came off quite well, really,” he said.
Watson said he did receive calls from townspeople about the tsunami.
“There’s supposed to be a big Halloween party downtown. People are calling, `Did the wave hit yet so we can go to the party?'” he said.
AP reporter Chris Weber in Los Angeles contributed to this report.