KUROSHIO, Japan — The simulations shocked this sleepy community on the tip of Japan’s Shikoku island: a huge undersea quake could bring a tsunami as high as 112 feet here, 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 quake of a similar magnitude has been met with alarm across the country.

The new simulations take into account the lessons learned from the 9.0-magnitude temblor 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 far wider — and far more populous — areas than the one last year.