Powerful M7.5 Earthquake Strikes Off Sanriku Coast, Tsunami Warnings Issued Across Northeastern Japan

Around 4:53 PM on April 20, 2026, a powerful earthquake with an estimated magnitude of 7.5 (preliminary) struck off the coast of Sanriku. A maximum seismic intensity of 5+ was observed in Aomori Prefecture. Following this earthquake, tsunami warnings were issued for the Pacific coasts of central Hokkaido, Aomori Prefecture, and Iwate Prefecture, urging widespread stringent caution.

Regions under tsunami warnings include the Pacific coasts of central Hokkaido, Aomori Prefecture, and Iwate Prefecture. Additionally, tsunami advisories were issued for the Pacific coasts of eastern Hokkaido, western Hokkaido, Miyagi Prefecture, and Fukushima Prefecture. The Japan Meteorological Agency (JMA) strongly urged all individuals near coastal areas or rivers to immediately evacuate to higher ground or other safe locations.

In fact, tsunamis were observed in various locations. A tsunami of 80cm was recorded at Kuji Port in Iwate Prefecture at 5:34 PM, and 40cm at Miyako Port at 5:22 PM. The tsunami reached Kamaishi Port at 5:19 PM, and a 20cm tsunami was confirmed in Ayukawa, Ishinomaki City, Miyagi Prefecture, at 6:02 PM. Government officials and experts emphasized the importance of continuing evacuation until tsunami warnings are lifted, without being misled by observed wave heights.

Sanae Takaichi, the Prime Minister (as reported), appealed on her X (formerly Twitter) account, urging residents in tsunami warning areas to “immediately evacuate to higher ground or evacuation buildings, or other safer elevated locations.” Miyako City in Iwate Prefecture issued evacuation orders for coastal areas via its disaster prevention radio system, strictly prohibiting approach to the vicinity of the coast. Local municipalities responded swiftly, with Ofunato City Hall opening multiple evacuation shelters and Kuji City Hall deciding to suspend all city bus routes.

The earthquake's impact extended to transportation, with the Tohoku Shinkansen suspending operations and sections of the Hachinohe Expressway closed. Civilian life was also affected, including the suspension of the evening broadcast of “Okaasan to Issho” (a popular children's program) due to the emergency. Akita Sub-Base of the Air Self-Defense Force dispatched a U-125A aircraft to collect damage information from above. Save the Children Japan also disseminated information regarding mental health care for children in emergency situations.

Continued vigilance against aftershocks is also necessary. Relevant organizations are urging people to remain fully attentive to future seismic activity and prioritize life-saving actions. Even a tsunami as low as 10cm can be extremely dangerous, so never approach the coast.

The Context

This news article describes a significant earthquake and subsequent tsunami event in Japan. For non-Japanese readers, several key points provide important background:

• Sanriku Coast: This region in northeastern Japan is highly susceptible to earthquakes and tsunamis due to its location along major tectonic plate boundaries. It was the area most devastated by the 2011 Great East Japan Earthquake and Tsunami.
• Seismic Intensity (Shindo): Japan uses its unique Shindo scale to measure the intensity of shaking at a specific location, distinct from the Richter scale which measures magnitude (the energy released at the epicenter). Shindo 5+ (or 5-kyō) indicates very strong shaking capable of causing significant damage, including widespread structural damage to houses and buildings, and making it difficult to stand.
• Tsunami Warnings and Advisories: Issued by the Japan Meteorological Agency (JMA), these signals have critical distinctions. A