KUSHIRO, Japan -- The violent jolt threw Sachiko Katsuta back into bed when she tried to go downstairs to her restaurant, where dozens of rice bowls had crashed to the floor.

Yet within hours of Friday's pre-dawn earthquake -- the world's most powerful in 2 1/2 years -- she and other residents of Japan's northern island of Hokkaido were counting themselves lucky and resuming life as usual. Aftershocks rocked the island again today. There were no reports of injuries or damage.

Damage from the magnitude-8 quake was relatively light, not only because it struck deep under the ocean but also because people in this quake-prone region were prepared. Power and water resumed after several hours.

And of more than 400 injuries, most were minor.

"I thought for sure this was the Big One," said Katsuta. "But it looks like we got by with just a few broken dishes and windows."

There were no reports of deaths directly caused by the temblor, which struck at 4:50 a.m. Two fishermen were missing, and police suspected they may have been swept away by tsunami, or ocean waves, that followed.

A wide swath of the island suffered damage: The quake buckled roads, capsized fishing boats, and caved in part of the ceiling of the airport in Kushiro, 560 miles northeast of Tokyo. The city of 190,000 people was believed to be one of the hardest hit, with power outages reported.

In the nearby city of Tomakomai, black smoke and flames rose into the sky from an oil tank fire. There were no injuries, and the fire was contained within hours. Officials said 188,700 barrels of crude were lost.

Still, experts said damage was moderate considering the size of the quake. It had an epicenter 26 miles beneath the ocean floor off Hokkaido's coast, and produced horizontal shaking rather than a vertical bounce.

"My first reaction was that the damage was much smaller than what earthquakes of that magnitude are capable of doing," said Yasuhiro Umeda, a seismologist at the Disaster Prevention Research Institute at Kyoto University.

Umeda said the swaying Friday was less violent that would have been expected but was felt across a wider area. He also credited the region's experience with strong temblors as helping to prevent a disaster.

Residents were shaken but stayed calm despite some 25 aftershocks -- at least one registering 7.1-magnitude -- that hit intermittently throughout the day. A few scattered buildings collapsed, but most buildings were constructed to withstand the rocking.

"We've had earthquakes here for as long as I can remember. For this one, I stayed in bed and put the covers over my head," said Kaori Maeda, 53, who cares for the elderly. "You're better off not trying to run around."

The quake -- centered in the Pacific about 60 miles off Hokkaido's eastern shore -- was the strongest since an 8.4-magnitude temblor June 23, 2001. That quake, near the coast of Peru, killed 74 people, the U.S. Geological Survey said.

Hokkaido government official Takeshi Matsumura said 455 people were confirmed injured late Friday. Most suffered minor scrapes caused by broken glass and falling objects or hurt themselves trying to flee. As many as 28 were seriously hurt, mostly with broken bones.

Japan's public broadcaster, NHK, put the injury toll at 479.

Though not listed as a quake-caused fatality, a 61-year-old man cleaning up broken bottles after the earthquake was struck by a car and died, police said. A 58-year-old man died while trying to sail to calm waters. Officials said he had heart problems and tsunami didn't appear to be the cause.

About 41,000 people were evacuated to shelters, but by evening, only 1,400 evacuees had not returned home, said Hiroyuki Nakao, a government spokesman.

Located along the Pacific "Ring of Fire," Japan is one of the world's most earthquake-prone countries. A magnitude 8 quake can cause tremendous damage in populated areas.

Earlier this month, Tokyo marked the 80th anniversary of a magnitude 8.3 quake that devastated the city and neighboring Yokohama, killing at least 140,000 people. In 1995, a magnitude 7.2 temblor in Kobe killed more than 6,000 people.

Hokkaido is the northernmost and most sparsely populated of Japan's major islands. A quake and tsunami on the western side of Hokkaido killed 230 people in 1993.

Though earthquake prediction is a nascent science, Japanese experts forecast Friday's quake six months ago, according to the San Francisco Chronicle. They estimated a 60 percent probability an 8.1 magnitude quake in the area over the next 30 years, the newspaper reported.