A powerful 7.7-magnitude earthquake shook northern Japan. The tsunami warning has now been canceled, but several areas remain under watch. Meanwhile, authorities have warned of the risk of a major "Mega-quake" to follow, ordering the evacuation of 171,000 people.
On 20 Apr 2026 GMT+7, NHK reported a strong 7.7-magnitude earthquake off northern Japan’s coast. This triggered tsunami warnings for several prefectures, which were later canceled. However, tsunami monitoring continues in many areas as the Japanese Meteorological Agency issued a warning about a possible "Mega-quake," a large earthquake with a magnitude estimated between 8.0 and 9.0, potentially to follow.
The Japan Meteorological Agency stated the earthquake occurred at 16:52 local time near the Sanriku coast of Iwate Prefecture, at a depth of about 19 kilometers. The magnitude was revised upward from 7.5 to 7.7. Following the quake, tsunami warnings were issued for Iwate’s coast, as well as the Pacific coastlines of Hokkaido and Aomori, with waves expected up to 3 meters, though these warnings were later lifted.
Nevertheless, tsunami watches remain in place for parts of Hokkaido, Aomori, Iwate, Miyagi, and Fukushima, where waves up to 1 meter high are possible. Reports indicated an 80-centimeter tsunami wave at Kuji Port in Iwate Prefecture with rising water levels. Waves of 40 centimeters were observed at ports in Miyako, Urakawa in Hokkaido, and Hachinohe in Aomori Prefecture.
The Japan Meteorological Agency also issued warnings about the risk of a very large earthquake or "Mega-quake" along two deep-sea trenches in the Pacific Ocean. This risk covers 182 cities from Hokkaido to Chiba Prefecture. Officials urged residents in seven prefectures to prepare for potential disasters, closely follow news updates, and monitor for potentially strong aftershocks up to magnitude 5 in the coming days.
The Japanese government disclosed that as of 18:45 local time, evacuation orders have been issued for at least 171,957 people across Hokkaido, Aomori, Iwate, Miyagi, and Fukushima Prefectures. An emergency operations center was immediately established at the Prime Minister’s Office following the quake.
Transportation systems were partly affected. The Tohoku Shinkansen train service was suspended between Tokyo and Shin-Aomori, while some segments of the Yamagata and Akita lines also halted service. The Tokai Shinkansen line continued to operate normally.
Reports indicate that Shin-Chitose and Sendai airports remain open and operational. Meanwhile, energy companies confirmed no abnormalities at the Fukushima Daiichi, Fukushima Daini, Higashidori, and Onagawa nuclear power plants, with no changes detected in radiation levels in surrounding areas.
Sources: NHK, BBC