Earthquake Advisory: Seismic Activity Increases off Northern Japan

After a magnitude 7.7 earthquake off Sanriku, the Pacific coast of northern Honshū, on April 20 caused shaking of 5 upper on the Japanese seismic intensity scale in Hashikami, Aomori, the Japan Meteorological Agency issued a warning that there was now a greater risk of a large earthquake occurring over the next week. This applies to 182 municipalities, mainly along the Pacific coast from Hokkaidō to Chiba. It is the second such announcement since the warning system was introduced in December 2022, following the first on December 8, 2025, for the same region.

While the likelihood of a large earthquake taking place is usually estimated at 0.1%, the warning indicates that this possibility has risen to 1%; it does not indicate that one will certainly happen. The Cabinet Office has called on residents to check their existing disaster preparations, as well as to be ready to evacuate rapidly and to always carry essential items, such as cash, personal ID (passports or residence cards, My Number cards, and the like), and necessary medications.

Data from the JMA shows a notable increase in the frequency of earthquakes in the region since November 2025. This is based on a comparison of the number of earthquakes with a seismic intensity of 1 or greater, centered in the sea off eastern Aomori, Iwate, and Miyagi Prefectures over the past 10 years.

It includes the December 8, 2025, earthquake with a magnitude of 7.5 and seismic intensity of 6 upper, and the April 20, 2026, earthquake with a magnitude of 7.7.

(Translated from Japanese. Banner image © Pixta.)