What averted disaster was the fact that the epicenter was 36 miles deep, under the ocean, reports CBS News Correspondent Barry Petersen.
Two fishermen were missing after the pre-dawn magnitude-8 quake, and police suspected they may have been swept away by tsunami, or ocean waves, that followed.
It was strong enough to knock books off shelves and plaster off the sides of buildings, reports Petersen, but most injuries were minor and damage relatively light.
Most of the injured on the northern island of Hokkaido suffered minor scrapes caused by broken glass and falling objects.
The 4:50 a.m. temblor also cracked roads, capsized fishing boats, and caved in part of the roof of the airport in Obihiro, a city of 200,000. Kushiro, 560 miles northeast of Tokyo, was believed to be the hardest hit.
It forced the evacuation of 41,000 people and left some 16,000 homes blacked out. But by evening, power had been restored to all but 2,000 homes and only 1,400 evacuees remained in shelters, said Hiroyuki Nakao, a local government spokesman.
Experts said the damage was surprisingly light.
"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.
It was the strongest earthquake in 2½ years, the U.S. Geological Survey said. On June 23, 2001, an 8.4 magnitude quake struck near the coast of Peru, killing 74 people, said Waverly Person of the USGS in Golden, Colo.
This earthquake was far strong than the earthquake that rocked Kobe, Japan, in 1995 and killed more than 6,000. Eighty years ago this month, a 8.3 temblor rocked Tokyo and killed at least 140,000.
Hokkaido government official Hidenori Hoshino said 323 people were confirmed injured as of 5 p.m., about 12 hours after the quake. Police said 24 were seriously hurt, mostly with broken bones.
Japan's public broadcaster, NHK, put the injury toll at 479.
Police were searching for a 69-year old man and a 66-year old man who were fishing near the mouth of a river on the eastern coast of Hokkaido, said spokesman Akihiro Ishikawa. Authorities believe they may have been washed away by the waves. Their cars remained parked near the river.
Black plumes of smoke and flames leapt from an oil tank in the city of Tomakomai. The fire was contained within three hours and no injuries were reported. Officials said 188,700 barrels of crude oil were lost.
Umeda cited a pair of "fortunate coincidences" concerning where — and how — the quake struck as reasons why the country fared so well.
Unlike the magnitude-7.2 earthquake that devastated Kobe in 1995 and was centered directly below that port city, the epicenter Friday was relatively remote: 26 miles under the seabed, 60 miles off the coast.
That may explain in part why tsunami waves that surged to shore were smaller than had been feared, he said. The government had warned residents to avoid coastal areas, but the highest waves recorded were only about four feet.
The earthquake also produced horizontal shaking rather than a vertical jolt. Umeda said such swaying is typically felt across a wider area but is less violent than an up-and-down thudding.
Several observers credited the preparedness of the region, whose residents have lived through several magnitude-7-plus earthquakes in recent decades, most recently in 1993.
"If a major earthquake hit somewhere without that kind of experience, there could be a panic," Umeda said.
Living in one of the world's most seismically active nations, Japanese are drilled from childhood on what to do in case of earthquakes — including turning off the gas, staying away from windows and knowing the location of evacuation areas.
Many people secure their furniture and keep emergency provisions, and building codes have been revised several times over the last few decades.
The last major earthquake struck in 1923, killing more than 140,000 people in a city then made mostly of wood.