Japan Prepares for Aftershocks and Tsunamis Following 7.7-Magnitude Sanriku Earthquake

Japan remains on high alert for a potential “huge” earthquake following a 7.7-magnitude quake that struck off the Sanriku coast on Monday, April 21, 2026, according to official warnings from the country’s meteorological agency.

The Japan Meteorological Agency has warned that earthquakes causing even stronger shaking could occur within the next week, with the risk of a quake measuring 8.0 magnitude or higher described as “relatively higher than during normal times.”

The initial quake, recorded at a depth of 10 kilometers (6.2 miles), triggered evacuation orders for thousands of residents in coastal areas of Iwate prefecture, located approximately 530 kilometers (330 miles) north of Tokyo, as well as in parts of Hokkaido.

Although tsunami warnings were lifted hours after the earthquake, authorities issued renewed alerts about the possibility of larger waves from potential aftershocks, urging continued preparedness across seven prefectures in northeastern Japan.

Local officials in affected areas, including Hokkaido, have been using loudspeakers to warn residents about possible tsunamis and to remain vigilant, particularly in communities nearest to the earthquake’s epicenter off the northeastern coast of Honshu.

The current alert echoes memories of the 2011 Great East Japan Earthquake, which triggered a devastating tsunami that killed more than 18,000 people and caused a meltdown at the Fukushima Daiichi nuclear power plant.

As of Friday, April 24, 2026, Japanese authorities continue to monitor seismic activity closely and maintain readiness for potential aftershocks, emphasizing that the situation remains dynamic and subject to change based on ongoing assessments.