A powerful 7.4-magnitude earthquake struck the Pacific Ocean about 100 kilometers off the coast of Miyako in Iwate Prefecture at 4:53 p.m. local time on Monday. As a result, authorities issued tsunami warnings across northern Japan, and tens of thousands of residents rushed to higher ground.
The Japan Meteorological Agency (JMA) reported a preliminary magnitude of 7.4. It said the quake struck at a shallow depth of just 10 kilometers. This type of quake often causes stronger shaking and raises the risk of tsunamis. Meanwhile, the US Geological Survey confirmed the magnitude. Shaking reached as far as Tokyo, where high-rise buildings swayed for several minutes.
What happened on the ground
Within moments of the tremor, emergency alerts flooded television screens across the northeast. Anchors on multiple channels invoked the 2011 Tōhoku disaster, urging residents to flee coastlines and riverbanks immediately. NHK displayed the message “Tsunami! Evacuate! Don’t turn back” in both Japanese and English.
Approximately 40 minutes after the main shock, a 5.6-magnitude aftershock struck the same area.Authorities warned that further aftershocks were likely.
The tsunami threat
The JMA issued its highest-level tsunami warning for Iwate, Aomori, and Hokkaido. It predicted waves of up to three meters along those coasts. At the same time, it issued lower-level advisories for nearby areas, with waves expected to reach up to one meter.
Waves arrived quickly. So far, the highest recorded wave reached about 80 centimeters at Kuji Port in Iwate. Waves of around 40 centimeters hit Miyako Port. In addition, officials confirmed wave activity at Hachinohe Port in Aomori and Urakawa in Hokkaido. Authorities are still processing data from Ofunato and Kamaishi ports.
However, officials stressed that the danger is not over. They urged residents to remain in safe locations. Second and third waves can be stronger than the first.
Government response
Prime Minister Sanae Takaichi convened an emergency task force and addressed reporters in Tokyo, calling on residents in warning zones to evacuate immediately to higher ground or designated evacuation buildings. She said authorities were doing their utmost to assess casualties, carry out search and rescue operations, and relay accurate information to the public in real time.
The Maritime Self-Defense Force scrambled an SH-60K helicopter to conduct aerial reconnaissance and support any rescue operations that might be required.
Infrastructure
The Tōhoku Shinkansen, which runs between Tokyo and Shin-Aomori, was suspended, as was the Akita Shinkansen, following power outages triggered by the quake. No resumption timeline was immediately available. Live footage broadcast by NHK showed vessels departing ports along the warning coast and heading to open water to avoid being caught in the surge.
What comes next
Several questions remain unanswered as the situation continues to develop. The JMA scheduled a press conference for 6:00 p.m. local time, at which casualty figures and a fuller damage assessment were expected. The status of nuclear-related facilities in the region had not been officially confirmed. Seismologists cautioned that aftershock activity could persist for days, and given that this stretch of the Sanriku Coast was the epicenter of the catastrophic 2011 disaster, the structural integrity of sea walls and coastal defenses will face intense scrutiny in the hours ahead.
The US Tsunami Warning Center said there was no threat to the coasts of California, Oregon, Washington, Alaska, or British Columbia.
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