A series of powerful earthquakes shook the northern Japanese island of Hokkaido early on Friday, killing one, injuring more than?479 people, causing widespread damage and blackouts and prompting officials to issue tidal wave warnings.

Japan's Meteorological Agency measured the initial quake at 8.0 on the Richter scale -- powerful enough to cause significant damage -- and warned residents of aftershocks.

Some quake-generated waves measuring about one meter (three feet) in height struck the eastern Hokkaido coast, washing away some empty cars, but no major wave damage was reported.

The focus of the first quake was 26 miles below the seabed in the Pacific Ocean near the port of Erimo, about 600 miles north of Tokyo.

A second quake measuring 5.8 on the Richter scale jolted Hokkaido about an hour later followed by another measuring 7.0.

The first quake struck at 4.50 a.m. local time as most of the population were sleeping.

NHK television said at least 479 people had been injured in the relatively lightly populated region.

Hiroaki Tanaka, a fire official in Kushiro on Hokkaido's east coast, said?that 47 people were being treated for injuries at hospitals in the city.

"The situation seems to be settling down. Aftershocks seem to be lessening. Injuries could rise though, if people head to hospitals in their own cars," he said by telephone. "We felt it shake for a very long time," he said of the quake.

Television pictures showed boats heading out to sea after the warning of a tsunami -- large waves caused by seismic activity.

"We want everyone to exercise care for a while," a meteorological agency official told a news conference, referring to the tsunami warning.

Minoru Kasahara, seismologist at Hokkaido University, said on television: "We should be alert for tsunami for a day or two."

Television pictures showed video of a fire and smoke billowing near an Idemitsu Kosan Co oil storage facility at a refinery in Tomakomai, a coastal city in southern Hokkaido.

The unlisted refiner later said it had closed the plant for safety reasons.

Other footage showed cracks in buildings and fallen tiles as well as items spilled from supermarket shelves.

Jiji news agency said the airport in the city of Kushiro had been closed after the ceiling of the control tower collapsed.

Highways were closed and rail services halted in many areas. A passenger train derailed, injuring one person, reports said.

Tsunami warning

The meteorological agency issued a tsunami warning for the coastal areas in eastern and central Hokkaido and a tsunami alert for the coastal areas in western Hokkaido as well as the northern Japanese prefectures of Aomori, Iwate, Miyagi and Fukushima.

The "warning" was later downgraded to an "alert."

In 1993, a tsunami caused by a quake measuring 7.8 killed about 200 people on the island of Okushiri, off western Hokkaido.

The US National Oceanic and Atmospheric Administration (NOAA) issued a tsunami warning for Russia as well as Japan. It also issued a lower-level tsunami watch for the Philippines, Taiwan, Guam, and a number of islands in the Pacific Ocean.

Hideki Watanabe, an official in the town of Erimo, said the quakes caused a power outage to an unspecified number of homes.

Shugeyuki Takagi, an official in the town of Urakawa near Erimo, said at least 11 people were injured there, all slightly.

The Hokkaido Electric Power Co said the quake triggered an automatic shutdown of its Tomato-Atsuma thermal power station in Atsuma and caused a blackout in nearby communities.

Operation of Hokkaido Electric's Tomari nuclear power station was not affected, NHK said.

Hokkaido, about the size of Austria, is the second largest of Japan's four main islands and has a population of more than five million. The capital, Sapporo, hosted the 1972 Winter Olympics.

Ring of fire

Memories are still vivid in Japan of the earthquake in the western city of Kobe that killed more than 6,400 people eight years ago. That quake measured 7.2 on the Richter scale.

The Great Kanto earthquake of September 1, 1923 measured 7.9 on the Richter scale and killed more than 140,000 people in Tokyo and the neighboring port city of Yokohama.

Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Ring of Fire, a zone of frequent earthquakes and volcanic eruptions and the location of the top 10 earthquakes in the world since 1900.

All of the top 10 measured an 8.5 magnitude or above.

The largest recorded earthquake in the world was a magnitude 9.5 in Chile on May 22, 1960.

The US Geological Survey rates earthquakes of 8.0 magnitude and higher as "great" and says there is an average of one per year in the world.

Until the Japan quake, none of 8.0 or higher had been recorded in 2003. There was none of that magnitude in 2002.

(China Daily September 26, 2003)