Residents of western Japan were warned of possible aftershocks yesterday after two strong earthquakes the previous day but authorities said the tremors were not directly linked to a cycle of major seismic activity that hits the region every century or so.

An earthquake measuring 7.4 on the open-ended Richter scale shook western Japan just before midnight on Sunday, forcing thousands to be temporarily evacuated as tsunami waves approached.

Public broadcaster NHK said more than 40 people were injured by the two earthquakes, which struck within five hours of each other. The first, early on Sunday evening, measured 6.9 on the Richter scale. Tsunamis measuring up to 90 cm (35 inches) hit some areas.

More than 5,000 people in Wakayama, Mie and other prefectures were temporarily evacuated, media reports said. Many of those who were injured had fallen or had been hit by falling objects.

Officials said there was a danger that the two earthquakes, measuring five on the Japanese intensity scale of seven, could be followed by strong aftershocks of a similar intensity.

“It’s possible that earthquakes with an intensity of around five could be detected from now on,” Junpei Uratani, an official at the Japan Meteorological Agency, told Reuters. Uratani said the quakes were not thought to be directly related to the Tonankai earthquake, a major recurring quake that has struck the area roughly every century for the past 500 years.

Last time it struck, in 1944 off the Kii Peninsula, near where Sunday’s quakes occurred, it killed about 1 000 people. Uratani said the government’s Earthquake Research Committee would convene yesterday to study the quakes.

<B>Masayuki Kitano</B>