Inadequate Warning System Left Asia at the Mercy of Tsunami
Nature

Reviewed by Hitoshi URABE

Article:
Inadequate Warning System Left Asia at the Mercy of Tsunami
Nature
http://www.nature.com/news/2005/050103/full/433003a.html

Comments:

The term tsunami is one of few Japanese expressions that became an internationally recognized word to specify a phenomenon. And it deserves to be so.

Facing the Pacific Ocean, which is a huge mass of water covering large and complicated crustal structure of earth, Japan has been prone to tsunami since before history. There are countless number of historical tales and stories in various parts of Japan depicting horrors of tsunami.

Tsunami is not a meteorological phenomenon, such as a storm where high waves are caused by winds. It is originally triggered by a tectonic activity, a cause of an earthquake. While earthquakes could exert tremendous destructive power, the area affected by it is, in relative terms, limited. But when such a tectonic activity occur in seabed, the energy is transferred to the water covering it, effectively creating an energy-charged mass of liquid, spreading out in all directions.

Tectonic activities in ocean beds are difficult to identify. Moreover, as earthquakes in the deep bottoms of the sea are not easy to detect and direct damages to human livelihood is rare, they tend not attract peoples' attention, except of geoscientists and planetologists.

Another factor is that tsunami, while conveying a tremendous amount of energy handed over from the earth's crust, is virtually indiscernible in the open sea. As was seen in the attack this time, vessels and boats traveling in the Indian Ocean were not able to even notice the tsunami energy passing right beneath them. It would raise the level of water a few centimeters at most in open sea. Tsunami becomes noticeable only when as it reaches the shallow waters and the waves, often described as a wall of water, begin to build up, then hitting the land, exerting all the energy it acquired far offshore.

As such, tsunami was considered an unpredictable hazard, an evil from the sea, an act of God - in a naive Christianity sense of the term.

It was well into the 20th century before a good understanding of the mechanism of tsunami was gained, and even then, it was considered impossible to formulate an effective system to avoid the damage. The only realistic means were to keep on maintaining and upgrading the dikes and coastal embankments - for tsunami that may attack someday in the unknown future - an often politically controversial agenda. And, of course, run to the hills when a bubbly line of water is observed in the horizon - as there may be a few minutes left to escape.

Then it was on May 22, 1960, when a large destructive earthquake off the coast of South Central Chile along the Peru-Chile Trench generated one of the most destructive tsunamis to hit Hawaii and the rest of the Pacific in 20th century. The earthquake itself was the largest in the century for the southern hemisphere. The earthquake and the tsunami were extremely destructive in Chile, where the casualty was estimated to range anywhere from 330 to 2000 people.

The Pacific-wide tsunami triggered by this earthquake raced across the ocean causing extensive destruction along its path. The tsunami traveled 17,000 kilometers in 22.5 hours to attack Japan. The fatality in Japan was 142, and left more than 30,000 people homeless, and over 160,000 people incurred some sort of damage.

This attack occurred when Japan was at the verge of the high-speed economic growth, finally recovering from the ashes of WWII. At the same time, backed by the recovery of economic health, growing was the people's aspiration for a modern society, where people's lives and rights would be respected. People turned their eyes to the hostile aspects of nature, and began to plan and implement means to dampen the potential damage. Experience of a similar, albeit somewhat smaller, earthquake and tsunami originated off Alaska coast in 1964 expedited the process.

While the traditional measures of improving dikes and coastal embankments continued, a system was devised and implemented to warn for tsunami. A network of seismometer was placed along the coast, to monitor the seismic activities beneath the Pacific Ocean. It was s significant step in coping with earthquakes in nearby seabed, but as evident in the case of the Chile quake, needed further enhancement. The system began cooperating with the similar facility in the U.S., and eventually grew to become an international network called International Tsunami Warning System (ITWS), which currently 26 states and regions subscribe.

Of course, no system can be perfect in terms of avoiding damage completely. In 1993, a tsunami struck the northern island of Hokkaido, killing 239 people. But very many more were saved because of the warning system and the messages conveyed by TV, radio, and other means, which were then received and reacted to by the people with sufficient understanding and recognition of the danger.

Such is the knowledge and experience Japan is offering to extend to those people living in the perimeter of the Indian Ocean, which should significantly, but unnoticeably in ordinary times, increase the safety of the people in the region.

One perhaps sarcastic comment being town-talked about in Japan. As the cost to establish and maintain such a system being tremendous, it was lucky for Japan that it could spend such money for such purpose, when many other countries had to devote their wealth to enhance military powers. Also, it was lucky for Japan to be surrounded (mostly) by friendly countries which allowed for productive exchange of knowledge and information, when in other regions the neighbors were often the enemies.