The massive onshore surges of seawater from tsunamis triggered by the mega-earthquake that struck off northwestern Indonesia on Sunday have caused heavy damage across southern Asia. They are a deadly reminder of how vulnerable humanity is to the destructive forces of nature.

The world’s fourth-largest outbreak of tsunamis in a century has left more than 20,000 dead and millions homeless in countries facing the Indian Ocean, including Sri Lanka, Indonesia, India, Malaysia and Thailand. Japan, which is no stranger to tsunami disasters, should provide long-term financial and technical assistance, not just emergency relief. At the same time, the nation should step up its own efforts to prepare for tsunamis spawned by earthquakes that are predicted to occur off the Pacific coast of central and western Japan.

There are always lessons and warnings to be drawn from a natural catastrophe. One flag raised in the latest tragedy is that there is no full-scale tsunami warning system in the Indian Ocean. Another is that coastal towns and villages in the region are almost defenseless against tidal waves in general. In particular, popular resort spots, such as Phuket, Thailand, have no tide embankments along their coastlines.

In the Pacific Ocean, a tsunami warning center was created in Hawaii following the 1960 Chilean earthquake. Warnings are issued on the basis of seismic waves recorded in Pacific Rim countries, which maintain an extensive observation network.

By contrast, countries facing the Indian Ocean are ill-prepared for tsunamis. They probably have observation facilities, but none appears to have any working network for transmitting tsunami information to residents, such as disaster hot lines. Nor do they appear to have adequate programs, including ready-to-use guidelines for evacuation, to enhance public awareness of tsunamis.

A tsunami travels very fast. The waves generated by the Chilean quake reached Japanese shores in just 24 hours, leaving 142 people dead or missing. Simple arithmetic shows that the tsunami raced a distance of about 17,000 km at 700 kph — about the same speed as a jetliner. The latest tsunami, unleashed by a 9.0-magnitude temblor that occurred off Aceh Province on the Indonesian island of Sumatra, is estimated to have reached Sri Lanka in about two hours. The lesson is obvious: If residents and visitors had been properly warned, much of the tragedy would have been prevented.

Japan should do everything it can to help build a tsunami warning system in the Indian Ocean, one that extends from southern Asia all the way to eastern Africa. For now, though, efforts should be focused on emergency assistance, especially medical supplies and sanitation aid to prevent the spread of infectious diseases.

This is also the time to examine our own efforts to cope with future tsunamis. According to the government’s Central Disaster Prevention Council, big earthquakes are likely to occur off the Pacific coast of central and western Japan (Tokai, Tonankai and Nankai regions). Such quakes, it says, will generate powerful tsunamis because, like the one Sunday, they will originate from tectonic movements in the seabed plates.

The maximum death toll in a tsunami from a Tokai temblor is estimated at 2,200. The number is expected to reach 8,600 if quakes hit the Tonankai and Nankai regions at the same time. To minimize damage, the government is promoting a program to make buildings more quake-resistant.

The first step in anti-tsunami efforts is to check and, if necessary, reinforce embankments. Beyond that, it is necessary to prepare “tsunami hazard maps” showing in detail how far the waves would advance beyond shorelines. Based on these maps, specific evacuation plans should be drawn up.

It is especially important to maintain an effective information system. The government plans to install wireless hot lines in all cities, towns and villages in fiscal 2005. The national average for prefecture-wide coverage by a disaster-prevention radio network was 68 percent, according to a March 2004 survey by the Fire and Disaster Management Agency. In the 23 prefectures likely to be hit by Tokai and Tonankai quakes, coverage ranged from 100 percent to 39 percent. In 10 prefectures it was below the national average.

The sobering thought is that there are limits to physical measures, such as building embankments, against tsunamis. A tsunami cannot be stopped in its tracks. Perhaps the best way to minimize casualties would be to evacuate early. A government study shows that the death toll from an early-morning Tokai quake would drop from a maximum of 2,200 to 700 if people were quickly evacuated.

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