Sunday's quake-triggered tsunami underscored how vulnerable--and perhaps helpless--Japan would be if a similar-sized temblor struck off its coast.

The disaster in South Asia has prompted Japanese authorities to review their warning and evacuation programs, with fresh attention to tourists.

Japan has learned from experience that speedy evacuation is key to minimizing casualties from a tidal wave.

But one grim figure remains--10 minutes.

Experts say some people have less than that to reach safety before a tsunami triggered by a quake off the Pacific coast reaches shore.

Should such a huge earthquake strike, the first tsunami of a meter high could hit shore in a few minutes, quickly followed by ones 10 meters high.

It took two to three hours before Sunday's tsunami pounded the Sri Lankan and Indian coasts, but there were apparently no evacuation warnings in those countries.

``In Japan, where tsunami will reach shore in a far shorter time, the warning system is even more important,'' says Masataka Ando, a professor at the Research Center for Seismology, Volcanology and Disaster Mitigation of Nagoya University.

The magnitude of the Indonesian quake was 9.0 on the Richter scale. In Japan, a Tokai earthquake, which experts warn could hit anytime, is expected to mark 8.0. If the Tonankai and Nankai quakes, which experts say could strike in the first half of this century, should occur simultaneously, the magnitude would be 8.6.

If all three hit at the same time, the magnitude would be 8.7, killing up to 28,000 people, including 12,700 who would perish in tsunami, according to estimates by the Central Disaster Management Council.

``Should they occur during the sea-bathing season or where waves become higher due to complex coastal geological features, the damage would be even greater,'' Ando said.

The Japan Meteorological Agency plans to issue a tsunami warning within three minutes after a temblor. But that could still be too late to enable coastal residents to evacuate to safety.

Other problems exist.

In some cases, municipalities failed to issue evacuation instructions in response to the agency's tsunami warning; in others, residents simply ignored an evacuation call.

Nobuo Shuto, a professor of tsunami engineering at Iwate Prefectural University, said residents in this quake-prone land should use their common sense.

``Even if a meteorological agency warning fails to reach them, the quake jolts are a natural tsunami warning,'' Shuto said. ``In low-lying areas with tsunami risks, people should know how they should react in such an eventuality.''

In Iwate and neighboring prefectures, the Sanriku Tsunami of 1896 and of 1933, triggered by quakes off the jagged Sanriku coast, killed about 22,000 and 3,000 people, respectively.

Fumio Yamashita, 81, of Ofunato, Iwate Prefecture, who has studied quake and tsunami damage, stressed the importance of handing down experiences of disasters.

``Memories of a disaster could be lost as many years often pass before the next one,'' said Yamashita, who survived the 1933 tsunami.

The Indian Ocean tragedy also awakened officials of Miyagi Prefecture and elsewhere to the need to properly warn tourists, who may not be familiar with the region.

Shizuoka Prefecture is taking other anti-tsunami steps, designating 258 tall, quake-resistant structures along coastlines as shelter from tidal waves. A huge floodgate that could block a tsunami of 5.8 meters was also completed in Numazu port in September to protect about 9,000 residents.(IHT/Asahi: December 29,2004)