Hardly any Japanese felt the earthquake in the distant north Pacific this week, but anyone watching television saw a tsunami warning almost instantly and thousands evacuated to higher ground within minutes.
While the waves that later rolled ashore on the northernmost main island of Hokkaido were only about 40cm high and claimed no lives nor caused much damage, a complex and high-tech network built up over decades has made possible swift dissemination of information vital to saving lives.
”We need to evacuate people before the tsunami strikes,” said Osamu Kamigaichi, an official at Japan Meteorological Agency’s (JMA) Earthquake and Tsunami Observations Division.
”It’s meaningless if it’s not speedy,” he said, adding that the agency aims to issue tsunami alerts within three to five minutes after a quake that occurs in or near Japan.
It took the agency longer after Wednesday’s estimated 8,1 magnitude earthquake as its epicentre was off Russia’s Kurile Islands, outside Japan’s monitoring range, but the first alert was out after 14 minutes.
This was in stark contrast to what happened on the Indonesian island of Java in July when over 600 people were killed by a tsunami as authorities failed to warn residents of the approaching waves triggered by an offshore earthquake.
At the heart of the Japanese network is JMA’s computerised Earthquake and Tsunami Observation System (ETOS) that monitors signals from 180 seismic stations across Japan and about 80 water-borne sensors 24 hours a day, 365 days a year.
Officials at the JMA’s central monitoring room in Tokyo sit in front of numerous computers and large flat-screen displays, some showing a map of Japan indicating where tsunamis have been recorded and others graphs of seismic activity.
But Kamigaichi said the monitoring and the warnings would be useless if they did not reach the public.
The weather agency and media have developed a system to superimpose alerts on TV screens as soon as they are issued, and in some areas, there is even a system that automatically turns on TVs in the event of an evacuation order.
”Everything is online. We’re not living in an age of phones or faxes any more,” Kamigaichi said.
In addition, warnings are sent to local governments via a satellite system in case land-based communications fail, and officials then activate sirens and loudspeaker systems if an evacuation advisory is needed.
Japan has offered its expertise to an international effort to create a warning system in the Indian Ocean following the December 26 2004 tsunami that left up to 232 000 people dead or missing in a dozen Indian Ocean nations.
And after the July earthquake off Java, Japanese officials warned their Indonesian counterparts of an likely tsunami, but the information was never passed on to the public.
Kamigaichi, who has visited Indonesia numerous times to share Japan’s skills, said building a warning system there would be a lengthy process given the lack of communications infrastructure and the various languages spoken throughout the large archipelago.
The word tsunami itself is Japanese — meaning ”harbour wave” — and reflects the long and often tragic battle with the phenomenon in the country that accounts for about 20% of the world’s earthquakes of magnitude 6 or greater.
In 1896, a magnitude 8,5 earthquake and tsunami left more than 22 000 dead in north-eastern Japan, and still vivid in many people’s memory is the 7,8 magnitude quake in 1993.
JMA’s warning system has been upgraded several times since its inception in 1952, including after the 1993 tsunami which struck a small island off Hokkaido even before warnings could be issued.
”It’s been a challenge for Japan all along,” said Kamigaichi. – Reuters