The simulations shocked this sleepy community nestled on the tip of Japan’s Shikoku island: A huge undersea earthquake could bring a tsunami as high as 34m, a government-appointed expert panel said. The waves could arrive in minutes and engulf most of the town, swallowing up even the foothills that the residents had counted on for high ground.
“We’d never make it if such big waves came,” said Hachiro Okumoto, 70, a fisherman who has worked off the Kuroshio coast for half a century. “It would be a wall of water. It would block out the sun.”
Just a year after a tsunami destroyed much of Japan’s northern Pacific coast, an updated hazard map detailing the damage that could be unleashed by another earthquake of a similar magnitude has been met with alarm across the country.
The new simulations take into account the lessons learned from the magnitude 9.0 earthquake that hit off the Japanese archipelago in March last year. The fault lines in this seismically volatile region could cause far bigger earthquakes than previously thought possible, spawning tsunamis affecting a far wider — and far more populous — area than the one last year.
According to the new study, released by the panel of seismic experts a week and a half ago, a magnitude 9.1 earthquake in the Nankai Trough off Japan would trigger intense shaking and tsunamis along a wide stretch of Japan, from Tokyo southward, an area many times longer than the Tohoku coastline that was ravaged last year.
According to the report, Niijima, an island about 160km south of Tokyo, could be hit by waves reaching 30m, overrunning most of the island’s inhabited areas. Shimoda, a popular beach town about 177km southwest of the capital, could be swamped by waves reaching 25m.
Waves higher than 9m could hit the historic capital of Kamakura, the industrial hub of Toyohashi, the dolphin-hunting town of Taiji and almost 50 other coastal cities and towns. Even central Tokyo could be hit by 3m waves, the study says.
About 70 percent of Japan’s population, and much of Japan’s industry and infrastructure, is concentrated along the Pacific coast, from the top of the main island of Honshu south to Shikoku and Kyushu islands.
The doomsday projections have worsened the frayed nerves of a country still uneasy after last year’s disaster, which killed almost 20,000 people along the Pacific coast and set off multiple meltdowns at the Fukushima Dai-ichi nuclear power plant.
“After a disaster of such unprecedented scale, there was a need to update our thinking to include previously unforeseen possibilities,” said Fumihiko Imamura, a tsunami specialist at Tohoku University in northeastern Japan and a member of the panel that drafted the hazard map. “These simulations highlight the need for communities to bolster their evacuation plans.”
Nowhere has the anxiety been more pronounced than Kuroshio, a popular surfing spot and whale-watching town of 13,000 on the southwest corner of Shikoku, Japan’s smallest main island. At an emergency local council meeting on March 31, when the simulations were announced, Mayor Katsuya Onishi declared the future of the town “in peril.”
The scale of the possible tsunami trumps all previous notions of the risks facing the town. Deadly tsunamis have been rare — the last few waves to reach Kuroshio, including one in 1946, did little damage.