Japan’s meteorological agency is warning that a magnitude 7.5 tremblor off Aomori has temporarily raised the odds — estimated at 1 per cent — of an over 8.0 magnitude megaquake within a week. Government models show a worst-case offshore quake could generate 30-metre tsunamis, leave up to 199,000 dead, destroy 220,000 buildings, and cause $198 billion worth of damage across 182 municipalities in the north
Japan
issued a megaquake alert on Tuesday after a magnitude 7.5 earthquake struck off the eastern coast of Aomori, the northernmost prefecture of Honshu, just below Hokkaido.
The quake caused limited damage — 34 mostly minor injuries and some harm to infrastructure and buildings.
Authorities stressed that the alert is not a forecast, noting the chance of an 8.0 or stronger earthquake is only about 1 per cent.
Still, they hope the advisory prompts readiness for a disaster comparable to the 2011 catastrophe, which killed nearly 20,000 people and triggered a nuclear crisis.
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Officials say the likelihood of a follow-up quake of magnitude 8 or higher is elevated over the next week. Residents, particularly along the coast, are being urged to stay prepared so they can quickly take their emergency bags and evacuate if a stronger quake strikes.
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Compared with a similar notice issued last year, this advisory was more measured. In summer 2024, a “Nankai Trough” megaquake advisory for Japan’s southern Pacific coast sparked confusion, panic buying of emergency food, cancellations of major events, and temporary business closures.
A megaquake alert for Japan’s northeastern coastline The Japan Meteorological Agency (JMA) said Monday’s strong quake briefly heightened seismic risks for regions in Hokkaido and the Sanriku coast.
This is where the Pacific Plate forms the Japan Trench and Chishima Trench, sites responsible for numerous major earthquakes.
Experts believe the deadly 2011 quake and tsunami originated from seismic movement along the Japan Trench, which runs from eastern Chiba to Aomori. The Chishima Trench extends from eastern Hokkaido to the northern islands and the Kurils.
Explaining the advisory, the JMA pointed to the sequence in 2011: the magnitude 9.0 quake that devastated much of northern Japan occurred two days after a magnitude 7.3 tremor off Iwate’s coast — the same region hit hard in Monday’s quake.
The 2011 disaster unleashed a massive tsunami that struck Iwate, Miyagi, and Fukushima prefectures, with waves reaching over 15 meters (50 fe
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