A powerful earthquake shook northwestern Pacific on Saturday at around 1:30 p.m. (0430 GMT), leading to tidal changes at Japan's northeast coast. A wave of 40 centimeters was observed at Ogasawara chain of islands.

At 4:56 p.m. (0756 GMT), a wave of some 40 centimeters was observed at Chichi island of the Ogasawara chain of islands in the Pacific, the NHK public television said. The subtropical island chain is around 1,000 Kilometers south of metropolitan Tokyo.

Tidal changes up to 20 centimeters were also observed at Nemuro and several other places along the coast of Japan's northern island of Hokkaido from 3:28 p.m. (0628 GMT) to 4:33 p.m. (0733 GMT). There were no immediate reports of casualty or damages.

The quake, which measured a magnitude of 8.3 degrees on the Richter scale, occurred at around 1:24 p.m. (0424 GMT). Its epicenter was 30 kilometers underground at 46.1 degrees northern latitude and 154.2 degrees eastern longitude, the agency said.

Under the Japanese seismic classification system, which measures the intensity of tremors on the Earth surface, the quake measured 3 degrees on some parts of Hokkaido including Kushiro, Hakodate and Nemuro, as well as at some places of Amori, Iwate and Miyagi prefectures.

According to a renewed tsunami warning issued at 3:28 p.m. (0628 GMT), waves as high as two meters could hit the northeastern coast of Japan's northern island of Hokkaido later in the day. Besides, a wave of around 50 centimeters will likely hit a large part of Japan's Pacific coastal areas from central Hokkaido to Wakayama prefecture in western Japan.

An evacuation advisory has been issued in 22 municipalities around the region, targeting a total of some 37,000 households, Kyodo News said. The Japanese government has set up a liaison office at the prime minister's office in Tokyo following the tsunami warning. Japan's coastal security authority has also issued sailing warnings.

On Nov. 15, 2006, a strong earthquake with a preliminary magnitude of 8.1 hit the disputed Etorofu Island off Hokkaido, which was not far from the epicenter of Saturday's quake and caused tides of 40 centimeters at Nemuro on Hokkaido's east coast.

Editor: Yan