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Aomori Quake Occurs in Area Hit by M7, M8 Earthquakes in Past, Hypocenter Located in Region of Anticipated Japan Trench Quake

The Associated Press
A tsunami warning is seen on a television in Yokohama on Monday after a strong earthquake rocked the Tohoku region and Hokkaido.

The Yomiuri Shimbun

15:46 JST, December 10, 2025

The powerful earthquake that struck late on Monday, with its epicenter off the east coast of Aomori Prefecture, occurred in an area that has been hit by quakes in the past measuring magnitude 7 and magnitude 8.

The hypocenter was located within the presumed focal region of an anticipated quake along the Japan Trench or Chishima Trench, which could result in at least 100,000 deaths. The government is on the alert because a larger follow-up earthquake may occur in the area.

The Monday earthquake occurred north of the epicenter of the magnitude 9 Great East Japan Earthquake that struck in 2011. It was a trench-type quake, like the March 2011 earthquake, occurring at the boundary between the Pacific Plate on the sea side and the North American Plate on the land side. The quake occurred as the Pacific Plate subducted beneath the North American Plate.

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Major earthquakes, including the magnitude 8 Tokachi-oki Earthquake in 2003 and the magnitude 7.6 Sanriku-Haruka-oki Earthquake in 1994, occurred in the area and its surroundings. Since the Monday tremor occurred in a “void” with few recorded earthquakes of comparable magnitude, some experts suggest it may have taken place after part of a plate boundary, which had not entirely broken, was ruptured.

The government’s Earthquake Research Committee has estimated that earthquakes of about magnitude 7.9 could occur in the area once every 97 years. According to the long-term assessment, earthquakes with a magnitude 7 to magnitude 7.5, which are of a similar magnitude to Monday’s tremor, could occur once every 8.8 years, and there is an “at least 90% probability” of the occurrence within the next 30 years.

“It is possible that the plate boundary deep underground, which had not moved, largely shifted,” said Tohoku University Prof. Shinji Toda, a seismology and geology specialist. “We need to be vigilant for larger follow-up quakes.”