Residents along Japan’s northern coast are once again on edge after a series of powerful earthquakes rattled the region in December 2025, prompting officials to issue an unprecedented megaquake advisory. The advisory, which covers 182 municipalities stretching from Hokkaido to Chiba prefecture, comes in the wake of a magnitude 7.5 earthquake that struck off the eastern coast of Aomori on December 9, followed by a magnitude 5.7 tremor northeast of Kuji just two days later. While the immediate damage has been modest—34 mostly mild injuries and some damage to roads and buildings—the psychological impact and memories of past disasters loom large.
The Japan Meteorological Agency (JMA) issued the megaquake advisory on December 10, 2025, warning of a heightened risk—albeit only about 1%—of a magnitude 8 or larger earthquake within the next week. This move, while not a prediction, is intended as a wake-up call for residents, particularly those living in coastal areas who are most vulnerable to tsunamis. "If a M7.0 or greater earthquake occurs in or around the probable source region of megaquakes along the Japan and Chishima Trenches, the possibility of a large earthquake is considered to be relatively high," the JMA explained, as reported by Newsweek.
Prime Minister Sanae Takaichi echoed these concerns, urging residents to be ready to evacuate at a moment’s notice and to pay close attention to updates from the JMA and local authorities. "Due to this earthquake, the likelihood of a large earthquake occurring from Hokkaido to the Sanriku offshore region is now assessed to be higher than normal. Accordingly, the ‘Off the Coast of Hokkaido and Sanriku Subsequent Earthquake Advisory’ has been issued," she said, according to The Sun.
Japan’s northern Pacific coast is no stranger to seismic activity. Kuji, a coastal city in far northeastern Iwate Prefecture, sits along the rugged Sanriku shoreline—a region notorious for its history of powerful earthquakes and devastating tsunamis. The area’s unique geology, where the Pacific Plate dives beneath the North American Plate, creates a major subduction zone and a hotbed for seismic events. The Japan Trench and Chishima Trench, both off the country’s northeastern coast, have been the source of many large quakes, including the catastrophic 2011 event.
The 2011 magnitude 9.0 earthquake and the resulting tsunami left an indelible mark on Japan, killing nearly 20,000 people and destroying the Fukushima Daiichi nuclear power plant. The tsunami, which soared above 15 meters (50 feet) in some areas, battered northern coastal towns in Iwate, Miyagi, and Fukushima prefectures. The disaster’s scars—both physical and emotional—continue to influence Japan’s approach to earthquake preparedness and disaster response.
Officials are now warning that a future offshore megaquake in the Hokkaido-Sanriku area could unleash a tsunami up to 30 meters (98 feet) high, potentially killing as many as 199,000 people, destroying up to 220,000 buildings, and causing economic damages estimated at 31 trillion yen (about $198 billion). In the harsh winter months, up to 42,000 people could suffer hypothermia as a result of such devastation, according to government estimates cited by the Associated Press and The Sun.
In response to the advisory, local governments have ramped up efforts to prepare for the worst. Municipalities covered by the warning have updated their websites, inspected stocks of relief goods and equipment, and tested communication systems for use at evacuation centers. Iwaki City in Fukushima has urged residents to register for emergency emails, while officials in Oarai, Ibaraki prefecture, have checked wireless communication devices to ensure rapid dissemination of information should disaster strike.
Residents are being encouraged to keep emergency bags packed with a few days’ worth of necessities, including shoes and helmets, and to sleep in day clothes rather than pajamas for a quick escape. Families are advised to discuss evacuation plans, and furniture should be secured to minimize injury risks during strong shaking. These recommendations, though simple, could make the difference between life and death in an emergency.
While the advisory is rooted in caution, officials have been careful to avoid causing unnecessary panic. The memory of last year’s Nankai Trough megaquake advisory, which was issued in August 2024 after a magnitude 7.1 quake off Miyazaki, is still fresh. That warning, heavy with scientific jargon, led to confusion, panic buying, and widespread event cancellations—even in areas outside the immediate risk zone. Supermarkets in western Japan and Tokyo saw shelves emptied of rice, dried noodles, bottled water, and portable toilets as people rushed to prepare for the worst.
Dr. Lucy Jones, a renowned CalTech seismologist, explained the rationale behind such advisories. "There was a 6.4 and we said, 'there's a 5% chance there could be something bigger in the next few days,' and we had a 7.1. That was that 1 in 20 chance and it actually happened," she told AP, referencing the 2019 Ridgecrest earthquakes in California. "Now when your first magnitude is 7.6, 5% to 10% chance of something bigger than that becomes a very consequential earthquake."
Seismologists, however, are quick to point out that earthquake prediction remains an elusive goal. As USA Today reports, "No one can predict earthquakes. However, by investigating faults and past quakes, scientists can better assess the likelihood of future earthquakes and how intense their shaking might be," the US Geological Survey (USGS) has stated. On average, the USGS expects about 16 major earthquakes worldwide each year, with roughly 15 at magnitude 7.0 or higher and one at 8.0 or above. Having two such large quakes—like the recent ones in Alaska and Japan—within days is not unprecedented, but it does serve as a stark reminder of the ever-present risk.
For residents of northern Japan, the recent tremors have revived painful memories. Daiki Shimohata, a civil servant in Hashikami, described the fear as the ground shook for about 20 seconds: "We were holding our children—a 2-year-old girl and a 1-year-old boy—in our arms. The shaking reminded me of the disaster (in 2011)," he told The Sun.
Despite the low probability of a megaquake in the immediate future, officials are urging vigilance rather than complacency. As Prime Minister Takaichi emphasized, "Regardless of whether your area was affected by this earthquake, residents in regions where disaster-preparedness measures are advised should, over the next week or so, pay close attention to information from the Japan Meteorological Agency and local authorities."
As the region waits, the hope is that the advisory will prompt preparedness, not panic, and that the lessons of the past will help mitigate the impact of whatever comes next.
