The Japan Meteorological Agency upgraded Monday’s earthquake off Iwate Prefecture to magnitude 7.7 and issued a rare mega-quake alert, warning residents in seven prefectures to prepare for a larger follow-on event. The government ordered 171,957 residents in Hokkaido, Aomori, Iwate, Miyagi and Fukushima prefectures to evacuate as tsunamis began striking the coast.
The quake, initially reported at 7.4 and later revised to 7.5 and then 7.7, struck at 4:52 pm local time off the coast of Sanriku, Iwate Prefecture, at a depth of 19 kilometres. JMA officials said there is an increased probability of a mega-quake along two deep-sea trenches in the Pacific Ocean. The alert covers 182 cities and towns stretching from Hokkaido to Chiba.
An 80-centimetre tsunami struck Kuji Port in Iwate Prefecture, with the water still rising, the agency said. Smaller 40-centimetre waves hit Miyako Port in Iwate, Urakawa Town in Hokkaido and Hachinohe Port in Aomori. Tsunami warnings remain in effect for Iwate Prefecture and the Pacific coasts of Hokkaido and Aomori, with waves up to three metres forecast. Advisories were extended to Miyagi and Fukushima.
Weather officials said the second and third waves could be higher than the first and urged residents under tsunami warnings not to return until warnings are lifted.
Class 3 long-period ground motion — strong enough to topple furniture and rock high-rise buildings — was recorded in Wakuya Town, Miyagi, and Yokote City, Akita. Shaking was felt as far as Tokyo, where buildings swayed for several minutes. The Tohoku Shinkansen suspended services between Tokyo and Shin-Aomori.
Public broadcaster NHK urged residents to move to higher ground immediately, invoking the March 2011 tsunami that killed more than 18,000 people. “Tsunami! Evacuate!” flashed across screens in English. “Don’t turn back,” the broadcaster warned. An anchor told residents along rivers and coastlines to “remember the 3/11 disaster.”
The government set up a task force at the crisis management centre of the Prime Minister’s Office. The 2011 Tōhoku earthquake also struck off Iwate’s coast and triggered the Fukushima Daiichi nuclear disaster.
