Japan's system should give advance warning of tsunamis
Japan’s seismic experts said Monday the country has a warning system in place that could outrace even lethal tsunamis like the ones that slammed southeast Asia on Sunday.
If everything goes as planned.
Fumio Imamura, a tsunami engineering expert and professor at Tohoku University Graduate School, said an offshore temblor similar to Sunday’s quake would cause a major disaster in Japan.
“Far worse causalities would be expected because most of the major cities in Japan are located along the shorelines,” he said — as are U.S. Naval bases Yokosuka and Sasebo and Marine and Air Force facilities on Okinawa.
“But, on the other hand,” Imamura said, “a disaster prevention system has been established in Japan.”
The country carefully calibrates the location and strength of earthquakes, to be able to give advance warning of the lethal, giant waves they trigger, called tsunami.
“As long as the system works as it should, the damage could be largely reduced,” Imamura said. “Should one step go wrong, however, the casualties could be far worse” than the Indonesian disaster.
The epicenter of Sunday’s 9.0 quake, among the strongest ever recorded, was west of Sumatra in the Indian Ocean. It was estimated to be from 310 miles to 621 miles long, said Assistant Professor Nobuyoshi Tsuji, University of Tokyo Earthquake Research Institute.
“If it happened in Japan, the seismic center would stretch from Tokyo … all the way to Aomori,” Tsuji said. He likened the earthquake’s impact to two major quakes striking Japan at the same time.
Japanese seismic experts estimate chances of a major earthquake striking along Japan’s Nankai and Tonankai fault lines sometime within the next 50 years at 80 percent, according to the Central Disaster Prevention Council of the Cabinet Office.
An earthquake along the Nankai fault could produce tsunami waves that would reach the Kansai district’s Kii Peninsula within 10 minutes, Tsuji said.
He said tsunami waves travel about 434 mph, as fast as a jet plane, at a depth of about 2.5 miles, the average depth of water in the world’s oceans.
“The Meteorological Agency monitors earthquake and tsunami activity at 300 points throughout the country,” Tsuji said, adding that once a tremor is registered, the agency immediately calculates whether a tsunami is expected to follow.
Imamura said the projected death toll for a major quake along the Nankai fault line is 7,000 to 8,000 people.
He said any earthquake stronger than a 6.5 magnitude on the Richter scale, with a seismic center less than 24 miles below the surface, could produce tsunami waves. The power of tsunami “is like a huge truck, which is running at 30 to 40 kph (up to 25 mph) when it hits you,” Imamura said.
“There is no way any house, not to mention a human being, can sustain the impact,” he said.
The Japan Meteorological Agency said a tsunami warning can be broadcast in less than five minutes.
“We can issue the warning or caution within three to five minutes should any tsunami be forecast to hit Japan,” said an official at the agency’s Disaster Prevention Information Center.
The information would be given simultaneously to major media, prefectural and municipal governments, he said.
“In Sanriku district, where tsunamis are frequent, water gates at every port will be closed when a warning is issued,” the official said. “It may not be possible to completely eliminate any casualties, but it is possible to largely reduce them.”