The 2016 Fukushima earthquake did not occur on the same fault that produced the devastating 2011 Tohoku disaster. Instead, the immense stress redistribution caused by that magnitude 9.1 megathrust loaded adjacent faults along Honshu's eastern coast, eventually triggering rupture on a shallower structure. The Japan Meteorological Agency officially categorized the 2016 event as an aftershock of the 2011 quake, a designation that speaks to the extraordinary timescale of seismic adjustment. The US Geological Survey measured its magnitude at 6.9, while the JMA settled on 7.4. Either way, the shaking reached intensity VII on the Mercalli scale -- strong enough to damage buildings and shift heavy furniture -- and registered 5 Lower on Japan's own Shindo scale.

Within an hour of the quake, the tsunami reached Fukushima's shore. Waves measured 0.9 meters at Onahama and 0.8 meters at Soma. To the north, Sendai Port recorded the highest wave at 1.4 meters. A later field survey found a local run-up of several meters at Ohama Fishing Port on Miyato Island, Higashimatsushima, where the surge damaged boats. Authorities had warned of waves up to three meters, prompting mass evacuations along the coast. Prefectures from Aomori to Chiba were placed on alert in quick succession, the warning network expanding outward in four separate announcements over the course of the morning. By 12:50 JST, all tsunami warnings were finally lifted.

The earthquake briefly shut down a spent fuel cooling system at the Fukushima Daini Nuclear Power Plant, a facility just 12 kilometers south of the ruined Fukushima Daiichi station that had melted down in 2011. The cooling interruption was short-lived, and monitoring instruments detected no measurable change in radiation levels. But the incident underscored the fragile psychology of a region still processing the world's worst nuclear accident since Chernobyl. Every tremor near Fukushima now carries a double weight -- the physical force of the shaking and the emotional freight of what happened before.

Remarkably, no one died. Seventeen people were injured, three critically, from broken bones and cuts caused by falling objects. A research facility in Iwaki caught fire. About 1,900 houses lost power briefly. Property damage was minor. The Nikkei futures market barely flinched. For a region that had buried nearly 20,000 people just five years earlier, the 2016 earthquake was a test passed -- evidence that upgraded warning systems, reinforced infrastructure, and a population drilled in disaster response could make the difference between catastrophe and close call. The earth may never rest along the Japan Trench, but neither does the vigilance of those who live above it.