Thirty-eight people were injured but there was no major damage from the pair of quakes that alerted seismic officials after striking within just five hours of each other in western Japan and off the coast of the central Tokai region on Sunday.

The tremors caused some panic, however, with hundreds of residents fleeing buildings after hitting Japan's west and centre measuring a revised 6.9 and 7.4 on the Richter scale respectively.

The meteorological agency warned of waves of up to one metre (3.3 feet) for coastal areas in western and central Japan, prompting some municipal governments to order residents to evacuate the area.

At least 3,600 people were temporarily evacuated to higher areas in Wakayama and Mie prefectures, which were hardest hit by the quakes, but they all returned to their homes early Monday, officials said.

Post-quake tsunami waves were observed in western and central regions.

Tsunami waves capsized 15 fishing boats and damaged three other boats in Mie prefecture, while roads were flooded in Osaka after water pipes there burst.

But the waves caused no major damage, and the agency lifted all its warnings in the early hours of Monday.

Hours after the quakes, officials said that they received no reports of major damage in the regions hit be the quakes.

"Many of the injuries were bruises that people suffered because they were startled by the quakes and fell," a Mie prefecture official said.

The meteorological agency's earthquakes division said it was analysing the two quakes to see if they were related.

Division head Masahiro Yamamoto said the agency had never before recorded two large quakes happening within such a short time frame and was investigating the phenomenon.

He said analysing the data could help the agency judge the likely timing of a large quake that seismologists believe is due to strike the Tokai region.

The size of Sunday's second earthquake, whose epicentre was in the Pacific Ocean off the Tokai region, was larger than the Kobe quake that measured 7.2 on the Richter scale and killed more than 6,000 people in January 1995.

Japan held disaster drills across the nation last week to mark the anniversary of the deadly Great Kanto Earthquake in 1923 and to prepare for the next big one.

The Kanto quake, the worst in Japan's recorded history, left more than 140,000 people dead or unaccounted for in and around Tokyo.

The most frequently forecast scenario for another major earthquake in Japan is one that could devastate the Tokai region from around Mount Fuji in the east to Mie prefecture in the west.

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