At 11:44 a.m. on December 12, 2025, northeastern Japan was rocked by a 6.9 magnitude earthquake, sending ripples of anxiety through a region all too familiar with seismic upheaval. The quake struck off the east coast of Aomori prefecture, at a depth of 20 kilometers (12.4 miles), according to the Japan Meteorological Agency (JMA). Within minutes, authorities issued a tsunami advisory, warning coastal residents of potential waves up to one meter high. The advisory was lifted about two hours later, but not before thousands received evacuation orders and the memory of past disasters was stirred anew.
This latest tremor comes hot on the heels of a far stronger jolt—a 7.5 magnitude earthquake that rattled the same region just four days earlier, on December 8. That earlier quake left at least 51 people injured, damaged roads and buildings, and triggered tsunami waves up to 70 centimeters in several communities, including Kuji port in Iwate prefecture. As reported by AP and The Japan Times, the timing of Monday's tsunami—striking at low tide—may have spared the coast from more severe flooding. "It was lucky that the highest tsunami in the Monday quake came at low tide, which means that the tide level is 1.5 metres lower than at high tide," explained Shunichi Koshimura, a professor at Tohoku University's International Research Institute of Disaster Science.
Friday's quake, while powerful, appears to have caused no serious injuries or major damage. Small tsunami waves, measuring around 20 centimeters, were recorded in both Aomori and neighboring Hokkaido prefectures. Bullet train services on the Tohoku Shinkansen Line were temporarily suspended between Sendai and Aomori due to power outages, according to JR East. Fortunately, the region’s nuclear facilities—including the Higashidori plant in Aomori, Onagawa in Miyagi, and the Fukushima Daiichi and Daini plants—reported no abnormalities. The Nuclear Regulation Authority assured the public there were “no immediate signs of abnormalities” at any of the affected sites, as NHK Japan reported.
The rapid-fire sequence of quakes has reignited concerns about the potential for an even larger disaster—a so-called "megaquake." After Monday’s 7.5 magnitude tremor, the JMA issued its highest-level megaquake advisory, valid through December 16. This was the first time since the advisory system’s launch in 2022 that such an alert had been raised. The warning, which remains in effect until just before midnight on December 15, covers the Pacific coast from Chiba, just east of Tokyo, all the way north to Hokkaido. Residents have been urged to stay vigilant, keep emergency kits handy, and be prepared to evacuate at short notice.
But what exactly is a megaquake, and why is Japan on such high alert? The archipelago sits at the intersection of several tectonic plates, making it one of the world’s most seismically active regions. The Japan Trench and Chishima Trench—deep cracks in the ocean floor off the east coast of Honshu and northern Hokkaido—are notorious for generating some of the most powerful earthquakes and tsunamis in Japanese history. The 2011 Tohoku earthquake, a magnitude 9.0 monster, killed nearly 20,000 people and triggered the Fukushima nuclear disaster. Historical patterns, according to the JMA and disaster science experts, show that magnitude-7 or higher quakes in these regions can sometimes be followed by even larger seismic events.
Fumiaki Tomita, associate professor at Tohoku University’s International Research Institute of Disaster Science, warned that the recent sequence of quakes is occurring along a historically active offshore fault zone where major earthquakes tend to happen in sequence. "Earthquakes with magnitudes of 8 could strike the area (if large-scale slips occur between the two plates)," Tomita said, as quoted by The Japan Times. He highlighted that the northern area off Iwate remains the only segment of this seismic zone that has not released a large earthquake since 1968. "Because unruptured segments can accumulate strain, they are more likely to produce powerful quakes and tsunamis," he explained. His advice? Communities along the Pacific coast from Hokkaido to Chiba should remain on high alert for both strong shaking and possible tsunamis, even after the current advisory expires.
The government’s megaquake advisory estimates that an offshore event of magnitude 8 or higher could unleash tsunami waves up to 98 feet (30 meters) high and potentially kill nearly 200,000 people. However, officials have been careful to emphasize that the advisory is not a prediction but a warning to improve preparedness. The probability of such a megaquake in the near term remains low—about 1%, according to government estimates—but the consequences of being caught off guard are too severe to ignore.
Friday’s main quake was followed by several aftershocks, with magnitudes ranging from 4.3 to 5.7, according to the JMA and USGS. A magnitude 5.7 tremor hit the same region at 12:21 p.m., just under an hour after the initial jolt. The Japanese emergency warning app NERV issued real-time updates, and evacuation orders were sent to thousands of residents in the most vulnerable coastal communities. The JMA also noted that no tsunami alerts were issued for the U.S. West Coast or Hawaii, underscoring that the threat was regional in scope.
Prime Minister Sanae Takaichi addressed the nation, clarifying that Friday’s earthquake did not fall under the earlier megaquake advisory. Still, she urged the public not to let their guard down. “The Japanese weather agency said that today’s quake was too weak to trigger a new megaquake advisory but advised the public to stay vigilant,” reported The Japan Times. In the aftermath, officials and experts alike stressed the importance of community preparedness and rapid response. The unpredictable timing of aftershocks and the possibility of late-arriving tsunami waves add to the complexity of disaster management. As Koshimura noted, "We have to be careful about the biggest wave, which may come late."
Japan’s recent seismic activity serves as a stark reminder of the country’s vulnerability—and resilience—in the face of natural disasters. While the latest earthquakes have, so far, resulted in only minor injuries and limited damage, the psychological impact and logistical disruptions are real. The temporary suspension of vital train lines, evacuation of coastal communities, and constant vigilance take their toll. Yet, the swift and coordinated response by authorities, scientists, and the public demonstrates Japan’s hard-earned expertise in disaster preparedness.
With the megaquake advisory still in effect and the unruptured Iwate fault looming as a potential source of future quakes, communities from Hokkaido to Chiba remain on alert. For now, life goes on—cautiously, but with determination. The lessons of past tragedies, like the 2011 Tohoku earthquake, continue to inform every warning, every drill, and every moment of readiness along Japan’s restless Pacific coast.
