By TAKURO YAMANO/ Staff Writer
April 7, 2022 at 07:00 JST
Pieces of a collapsed wall block part of a street in Oita after a strong earthquake hit Jan. 22. (Shoma Fujiwaki)
It’s not just Tokyo that faces the risk of being struck by a powerful earthquake with a magnitude of 7 or higher within 30 years. The same goes for the nation’s southern islands of Kyushu and Okinawa, experts say.
The government’s Headquarters for Earthquake Research Promotion said March 25 there is a roughly 80-percent probability of a quake in the range of magnitude of 7 to 7.5 hitting the Hyuganada Sea off Miyazaki Prefecture and a 90-percent or higher likelihood of such a temblor occurring around Yonagunijima island in Okinawa Prefecture.
The experts also said quakes with a magnitude of around 8 could occur in Hyuganada as well as around the southwestern Nansei Islands including Yonagunijima.
“Data available for these sea areas are limited compared with inland areas,” said Naoshi Hirata, head of the headquarters’ Earthquake Research Committee. “A large uncertainty remains, and even stronger earthquakes and tsunami could strike.”
Since 1919, magnitude 7-class quakes have struck Hyuganada and around Yonagunijima five and 12 times, respectively.
The risk of a magnitude 7 to 7.5 quake is estimated at around 60 percent for areas northwest of the Nansei Islands, which lie north of Okinawa’s main island. The probability of a magnitude 6.7 to 7.4 temblor occurring in a plate sinking in the Akinada, Iyonada and Bungo Suido waters was put at 40 percent.
The headquarters said a temblor that hit Hyuganada in 1662 might have been a megaquake and a magnitude 8 earthquake occurred around the Nansei Islands in 1911, an earthquake with a magnitude of around 8 could occur in these two areas in the future.
The headquarters also released the results of its first long-term assessment of possible quakes along offshore active fault lines.
The possibility of an earthquake with a magnitude of 7 or higher is estimated at 8 to 13 percent in waters off Tottori Prefecture through Kyushu in the southwestern part of the Sea of Japan.
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