Japanese scientists say they have developed a system that can detect quake-induced tsunami even when the temblor in question is of low magnitude and not considered serious enough to issue a warning.
Researchers with the Geographical Survey Institute (GSI) said they plan to announce the technology at the U.N. World Conference on Disaster Reduction, in Kobe.
The tsunami early warning system now operated by the Japan Meteorological Agency comprises a network of seismographs. Warnings or advisories are issued only after experts decide a tsunami could occur or is imminent. This requires officials to study the Richter scale magnitude of the earthquake as well as the location and depth of the epicenter.
But the seismographs cannot detect seismic waves that last for long periods, for example, for tens of seconds. This means the equipment may calculate a low magnitude for seismic waves not thought strong enough to cause earthquake damage but which could still lead to tsunami. As a result, a tsunami warning or advisory may not be issued in time, or at all.
But now, GSI researchers say they have overcome technological problems by developing a system that is more sensitive to slower moving seismic waves that are prolonged. They did this by utilizing the GPS set up at about 1,200 observation points around Japan.
Improvements in communications technology and better analytical methods mean that quake-induced tsunami can be observed instantaneously.
Because of current limitations on assessing likely impact, only about 30 observation points can now conduct instantaneous observations. By using more computers, however, the new technology can be applied to all observation points, researchers said.
Combining this approach with the early warning system used by the Japan Meteorological Agency, a more exact tsunami early warning system could be constructed, sources said.
As the world learned Dec. 26, quake-induced tsunami can be devastating. Just because a temblor is weak, it doesn’t mean it won’t generate considerable tidal waves. The problem is that evacuation orders frequently are not issued when an offshore earthquake is considered modest.
The death toll from the disaster in the Indian Ocean has already climbed above 160,000. The Meiji Sanriku tsunami in 1896 took about 20,000 lives.
Experts are keen to have a better system in place because of the probability that devastating Tonankai and Nankai quakes will hit within the next four decades.
The earthquake off Sumatra that led to the catastrophic tsunami in late December involved the slow slippage of faults. The seismic-wave period was analyzed to be about 100 seconds by scientists at the Building Research Institute here.