Japanese authorities have issued a special advisory warning of an elevated risk of a magnitude 8.0 or stronger earthquake in the coming days, after a powerful 7.7-magnitude quake struck in Pacific waters off the country's north-eastern coast on Monday. The Japan Meteorological Agency (JMA) said the likelihood of another major quake was "relatively higher than during normal times," with officials cautioning that aftershocks over the next two to three days could produce "even stronger shaking" than the initial jolt.

The earthquake struck at 4:53pm local time in waters off Iwate prefecture — a coastal region on Japan's main island of Honshu, roughly 530 kilometres north of Tokyo — at a depth of 10 kilometres. The tremors were felt across a vast area, including in large buildings in the capital. Municipalities in the affected region issued evacuation directives to more than 182,000 residents, urging them to move to higher ground or designated evacuation buildings. An 80-centimetre tsunami wave struck a port in Kuji, Iwate, around 40 minutes after the quake, though the initial tsunami warning — the second-highest of three alert levels — was later downgraded to an advisory, with possible waves of up to one metre forecast along parts of the northeastern Pacific coast. One person in the neighbouring prefecture of Aomori was reported injured after a fall; no major structural damage or casualties were immediately confirmed.

Prime Minister Sanae Takaichi urged residents in affected areas to evacuate to "higher, safer places," and her office established a crisis management team. Japan's chief cabinet secretary Minoru Kihara told reporters that bullet train services had been disrupted and around 100 homes had lost power, but that no serious damage had been identified. The JMA reminded the public that tsunami waves can strike repeatedly and urged people not to return to low-lying areas until all warnings were lifted.

The event has stirred deep anxiety in Japan, which remains scarred by the catastrophic 9.0-magnitude earthquake and tsunami of March 2011 — the most powerful quake ever recorded in the country — that killed or left missing around 18,500 people and triggered a meltdown at the Fukushima Daiichi nuclear plant, one of the worst nuclear disasters in history. Monday's quake struck in waters to the north of that same coastline. Japan sits atop four major tectonic plates along the Pacific "Ring of Fire" and experiences approximately 1,500 earthquakes a year, accounting for a significant share of the world's most powerful tremors.

This is not the first time in recent years that Japan has faced elevated seismic alerts. In 2024, the JMA issued its first-ever special advisory warning of a potential "megaquake" along the Nankai Trough, an 800-kilometre undersea trench off Japan's southern coast where tectonic plates are slowly converging. A further advisory was issued in December 2025 after a magnitude-7.5 quake struck off the northern coast. Authorities have estimated that a major Nankai Trough event could kill up to 298,000 people and cause around two trillion US dollars in damage — figures that lend urgency to each new seismic warning the agency issues.