Japan Tsunami Warning to Advisory After 7.7 Earthquake

Published: 20 April 2026. The English Chronicle Desk. The English Chronicle Online

Japanese authorities have downgraded tsunami warnings to advisories across the country’s northeastern coast following a powerful magnitude 7.7 earthquake that struck late Monday afternoon. The tremor, which occurred at 4:53 p.m. local time off the Sanriku coast, was initially reported as a magnitude 7.5 before being upwardly revised. While the initial “Major Tsunami Warning” sparked panic and forced the evacuation of approximately 156,000 residents across five prefectures, the Japan Meteorological Agency (JMA) eased the alerts after waves reached a maximum recorded height of 80 centimeters at Kuji Port in Iwate.

Residents in the affected regions described the onset of the quake as a “low, heavy rumbling” that seemed to vibrate through the ground seconds before the violent shaking began. “It didn’t feel like a sharp jolt at first,” said one shopkeeper in Hachinohe, Aomori Prefecture, where the tremor registered an “upper 6” on the Shindo seismic intensity scale. “It was a deep sound, like a very heavy train passing right under the floor. Then everything started to throw itself off the shelves.” In Hokkaido and Iwate, witnesses reported seeing the sea “swell and retreat” in an eerie rhythm shortly after the sirens began to wail, prompting a mass exodus to higher ground.

The quake’s epicenter was located approximately 80 kilometers off the coast at a depth of 19 kilometers, a shallow point that typically increases the risk of significant tsunami activity.

Metric	Initial Report	Revised Data (JMA)
Magnitude	7.5 $M_w$	7.7 $M_w$
Depth	10 km	19 km
Max Shindo	Upper 5	Upper 6 (Hachinohe)
Highest Wave	3.0 m (Predicted)	0.8 m (Observed)

Despite the downgrading of the tsunami threat, the JMA has issued a high-level “Megaquake Advisory,” urging residents to remain on alert for at least one week. Under the protocol established after the 2011 disaster, any significant quake in this region triggers a period of heightened monitoring. “History tells us that a magnitude 7 event can often be a foreshock to something much larger,” a JMA official stated during a televised briefing. “The likelihood of a secondary, powerful tremor is particularly high over the next 72 hours.”

As of Monday evening, no major injuries or catastrophic structural damages have been reported, though approximately 30 people were treated for minor injuries related to falls and broken glass. Crucially, the region’s nuclear facilities—including the Onagawa and Higashidori plants—reported “no irregularities” following emergency inspections. While some Shinkansen bullet train services between Sendai and Tokyo faced significant delays, most regional transport networks were back in operation by nightfall.

For the people of northeastern Japan, the “low rumbling” of the earth remains a haunting reminder of the 2011 tragedy. While the 2026 event appears to have spared the coastline from a major disaster, the sight of thousands of citizens moving in disciplined silence toward evacuation towers proves that the lessons of the past are deeply ingrained. As the tsunami advisories remain in place, coastal residents are being told to stay away from beaches and river mouths, as the sea remains “unpredictable and restless.”

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