From correspondents in Tokyo

TWO small tsunamis hit coastal areas of Japan's northernmost main island of Hokkaido following a powerful earthquake with a preliminary magnitude of 8.1 near Etorofu Island, the Japan Meteorological Agency said.

A 40cm tsunami hit Nemuro, on the east coast of Hokkaido, 11.29pm (AEDT) last night.

About 20 minutes later, a 20cm tsunami struck Kushiro, a city down the coast from Nemuro. There are no immediate reports of injuries or damage.

The two tsunamis came after the agency issued a tsunami warning covering a wide area of Japan's Pacific coast on the main island of Honshu and coastal areas of Hokkaido.

The town of Kushiro in Hokkaido registered an earthquake with an intensity of 2 on the Japanese seismic scale of 7.

The agency said a tsunami of 50cm is expected to hit wide areas of the Pacific coast of Honshu between the Tohoku and Tokai regions.

Local governments in Hokkaido and other prefectures ordered residents of coastal areas to evacuate to higher ground.

The Japanese Government set up an emergency liaison office to deal with the situation.

The quake occurred about 390km off Etorofu at around 10.15pm.

Etorofu is one of the four islands off Hokkaido, known in Japan as the Northern Territories and in Russia as the southern part of the Kuril Islands, which both countries claim as their own.

The islands were occupied by Soviet troops shortly after World War II.

News.com.au

Relief as Pacific tsunami fizzles out

Tokyo - Coastal residents voiced relief Thursday as one of the biggest earthquakes in recent times did little more than flip over boats in a scare that demonstrated Japan's quick-moving tsunami alert system.

The earthquake, with a magnitude of at least 8.1, struck late Wednesday in the northern Pacific Ocean northeast of Japan, triggering alerts stretching from Indonesia to California.

In Japan, authorities urged some 130,000 people to evacuate to higher ground in fear of the seismic waves. With memories of the devastating 2004 Indian Ocean tsunami still fresh, hundreds of cars rushed to the hills.

The Japan Meteorological Agency had warned of waves up to two metres (six and a half feet), but the biggest of a series of tsunamis to hit northern Japan was just 40 centimetres (16 inches).

"We all felt relieved when the tsunami warning was lifted," said Takeshi Tanaka, an official of the Fishermen's Association of Nemuro, which faces the Kuril chain -- the closest land to the quake's epicentre.

"Some of our fishermen scrambled to sail offshore while others harbored at safer areas of the port," Tanaka said.

"We are glad to hear that there was no damage to any boats, the most important means for our livelihoods," he said, adding that fishermen sailed out before dawn on Thursday and were catching fish as usual.

The US Geological Survey put the quake at 8.3 on the Richter scale, making it the 19th most powerful tremor ever recorded.

The underwater earthquake that triggered the December 2004 tsunami measured 9.1, the third strongest in recorded history. The disaster killed 220,000 people around the Indian Ocean coast, many of them struck without warning.

Japan, home to 20 per cent of the world's major earthquakes, prides itself on having one of the world's more accurate systems for predicting tsunamis.

The meteorological agency issued the tsunami warning 14 minutes after the earthquake occurred at 8:15 pm (1115 GMT) -- and eight minutes before it reported the quake itself, owing to the remote location.

"Tsunami information has priority as it has a sense of urgency in terms of disaster prevention," said an agency official.

"Our expected waves were higher than the actual ones because we needed to issue it as quickly as possible even if some calculation errors may be included in the data," he said.

Last month, the meteorological agency further upgraded its tsunami warning system, which can technically provide data less than two minutes after a big jolt.

"But it took us longer time than usual because the epicentre was far from our seismic intensity gauges," the agency official said.

Japanese and US seismologists released tsunami data through international channels including to Russia, which disputes some of the Kuril island chain with Japan.

No damage or casualties were immediately reported from the Kuril islands, according to Russian officials.

Across the Pacific in California, two docks were damaged and several boats were tossed onto dry land from the force of the tsunami.

"It was a tidal surge, about two or three feet of water, it kept coming and going for 20 minutes, it was very violent," said Paul McAndrews, harbor facility manager in Crescent City, around 560 kilometres (355 miles) north of San Francisco.

Three small fishing boats were also overturned in Miyagi on Japan's main island of Honshu, a prefectural government official said.

In Nemuro, the Japanese city facing the disputed Kuril islands, all residents who were evacuated have returned home "and are full of relief," said Yasukazu Imai, a city official.

"There was anxiety among residents following the tsunami warning but at the same time there was no chaos or confusion as we delivered the warning to our residents smoothly in line with our disaster relief manual," Imai said.

The Nation