Officials warn of elevated short-term risk but urge calm
Japan issued a megaquake advisory on Tuesday after a magnitude 7.5 earthquake struck off the eastern coast of Aomori, near Hokkaido. The quake caused 34 mostly mild injuries and some structural damage, but officials emphasized the alert is not a prediction. The probability of a magnitude 8 or larger quake in the coming week is estimated at only about 1%.
Even so, authorities hope the advisory will prompt residents to prepare for the possibility of a major event similar to the 2011 disaster that killed nearly 20,000 people and triggered the Fukushima nuclear meltdown. The alert follows concerns that seismic activity along the Japan Trench and Chishima Trench temporarily increases the likelihood of a stronger follow-up quake.
Why the northern coast is under heightened scrutiny
The Japan Meteorological Agency said risks around Hokkaido and the Sanriku coastline have risen due to shifting stress along the offshore fault systems. The trenches off Japan’s northeastern coast have produced multiple large earthquakes, including the magnitude 9.0 catastrophe in 2011. That quake was preceded by a magnitude 7.3 tremor just two days earlier in a similar pattern to this week’s activity.
The government estimates that another offshore megaquake in the Hokkaido-Sanriku area could unleash a 30-meter (98-foot) tsunami, kill up to 199,000 people, destroy 220,000 buildings and inflict as much as 31 trillion yen ($198 billion) in economic damage. The latest advisory covers 182 municipalities from Hokkaido through Chiba.
Japan separately maintains a high-risk advisory for the southern Pacific coast due to the Nankai Trough. A 2013 government scenario projected that a magnitude 9.1 quake there could produce a tsunami exceeding 10 meters, potentially killing 323,000 people and causing more than 200 trillion yen ($1.28 trillion) in losses.
Residents told to prepare, not panic
Officials stressed that the advisory is precautionary. “There is no prediction for a megaquake at any specific time or place,” disaster prevention official Tsukasa Morikubo said, urging residents to continue daily routines while staying ready.
Households are encouraged to keep an emergency bag stocked for several days, secure heavy furniture, and discuss evacuation routes. Coastal residents are advised to sleep in clothing suitable for immediate evacuation. Municipal governments across the region have begun inspecting relief supplies and communication equipment.
The communication around this advisory is more measured than the 2024 Nankai Trough alert, which triggered widespread confusion, panic buying, and event cancellations. Some travelers postponed holidays, and supermarkets in western Japan and even Tokyo saw shelves emptied despite being outside the at-risk zone.
A nation balancing vigilance and fatigue
Local officials are working to avoid similar public anxiety this time. Cities such as Iwaki in Fukushima are urging residents to register for emergency notifications, while towns like Oarai in Ibaraki are testing wireless alert systems. Though the likelihood of a large follow-up quake remains low, authorities say readiness remains essential in one of the world’s most seismically active regions.
