Japanese authorities issued a tsunami warning after a powerful earthquake struck off the Sanriku coast on Monday, triggering coastal alerts, transport disruption, and safety checks at nuclear facilities. Officials later measured the quake at magnitude 7.4, while AP, citing the Japan Meteorological Agency, reported a preliminary magnitude of 7.5 at a depth of about 10 kilometres.
The earthquake struck northeastern Japan at 4:53 p.m. local time. Authorities warned that tsunami waves could reach up to 3 metres along parts of the northern coastline. They also urged residents in affected areas to move away from the coast and rivers and seek higher ground.
Officials located the epicentre off the Sanriku coast at 39.8° N and 143.2° E. The quake registered an upper 5 on Japan’s seismic intensity scale, indicating strong shaking that could make movement difficult and topple unsecured furniture.
AP later reported that tsunami waves of about 80 centimetres reached Kuji port in Iwate Prefecture, while a smaller wave was also recorded elsewhere in the prefecture. At that stage, authorities kept the tsunami alert and advisory in place, although the Pacific Tsunami Warning Centre later said the broader tsunami threat had passed.
Officials also temporarily halted Tohoku Shinkansen services between Tokyo and Shin-Aomori after the quake. They took the precaution while assessing the impact of the shaking on infrastructure.
BREAKING: An earthquake with a magnitude of 7.5 has struck off the coast of Japanhttps://t.co/PjmaX8xAV6
📺 Sky 501, Virgin 602, Freeview 233 and YouTube pic.twitter.com/8RxD8lwhtL
— Sky News (@SkyNews) April 20, 2026The disruption added to the wider emergency response, as authorities worked to assess possible damage and continued urging caution in coastal and northern regions.
Tokyo Electric Power Company said it was checking whether the quake had caused any disruption at the Fukushima Daiichi and Daini nuclear plants. Tohoku Electric Power also began system checks at its Onagawa nuclear power plant.
AP reported later that Japan’s Nuclear Regulation Authority said nuclear plants and related facilities in the region were intact, with no abnormalities detected. The quake struck at a depth of about 10 kilometres, and earlier international reporting briefly listed the magnitude at 7.3 before later revisions.
