On Monday afternoon at 4:53, an earthquake measuring 7.5 struck off the coast of northern Japan. The tremor occurred along the Japan Trench, the same fault line that caused the devastating 2011 Tōhoku earthquake. Residents in fishing towns immediately fled to higher ground, remembering the deadly tsunami from fifteen years earlier.
In the port city of Kuji, the sea rose about 80 centimeters. Although officials had initially warned of a three-meter wave, the tsunami threat was quickly downgraded and eventually lifted. However, the earthquake shook buildings across the country, reaching Tokyo hundreds of kilometers away.
What made this event truly significant was what happened next. The Japan Meteorological Agency issued a rare "Subsequent Earthquake Advisory," only the second time in history. This warning raised the probability of a magnitude 8 earthquake in the region from 0.1% to 1% over the next week, affecting 182 coastal municipalities from Hokkaido to Chiba Prefecture.
The response was swift. Evacuation orders went out across three prefectures, and the Tōhoku Shinkansen high-speed train was suspended. Prime Minister Sanae Takaichi established an emergency task force. Fortunately, no deaths were reported, and nuclear facilities reported no damage.
For the Sanriku coast, a region scarred by centuries of major earthquakes, this advisory means one week of heightened alertness and caution.