A collapsed road off the coast of Aomori Prefecture due to an earthquake on the 8th. Kyodo, Reuters, Yonhap News

The Japan Meteorological Agency announced that an earthquake, estimated to be magnitude 6.7, occurred off the coast of Aomori Prefecture in northeastern Honshu at approximately 11:44 AM on the 12th. A powerful magnitude 7.5 earthquake had struck the same area on the night of the 8th.

According to Kyodo News and NHK, the agency initially announced the earthquake's magnitude as 6.5 but later revised it upwards to 6.7. The depth of the hypocenter was approximately 20 km.

The Japan Meteorological Agency issued a tsunami advisory for the southern part of Hokkaido and the Pacific coast of northeastern Honshu. In Japan, a tsunami advisory is issued when a tsunami of 0.2 to 1 meter in height is predicted.

Tsunamis with a maximum height of 20 cm were observed at Hachinohe Port in Aomori Prefecture and in Erimo Town, Hokkaido.

Shaking with an intensity of 4 on the Japanese seismic intensity scale was detected in parts of Aomori, Iwate, Miyagi, Akita prefectures, and Hokkaido.

Unlike "magnitude," which indicates absolute intensity, the seismic intensity (Shindo) on the Japanese scale is a relative concept that quantifies the shaking felt by people and the movement of objects in a specific area when an earthquake occurs.

An intensity of 4 signifies shaking that startles most people, causing hanging ceiling lights to sway significantly.

No abnormalities were reported at the Higashidori Nuclear Power Plant in Aomori Prefecture, its spent nuclear fuel facilities, or the Onagawa Nuclear Power Plant in Miyagi Prefecture.

Kyodo News reported that there is no concern of the Hachinohe City transmission tower in Aomori Prefecture, which sustained some damage in the major earthquake on the 8th, collapsing.

Location of the earthquake that occurred at approximately 11:44 AM on the 12th. Captured from the Japan Meteorological Agency website.

The Japanese government had previously issued a "Cautionary Information for Aftershocks off Hokkaido and Sanriku Coasts" for the first time following the major earthquake on the 8th.

This advisory, which began operation in December 2022, covers the Pacific coast of Honshu, from Hokkaido and Aomori Prefecture down to Chiba Prefecture near Tokyo. The current advisory is in effect until 0:00 AM on the 16th.

The aftershock caution is issued when a magnitude 7.0 or greater earthquake occurs in a focal region where a mega-earthquake is anticipated along the Japan Trench and the Kuril Trench, and it is determined that the possibility of a larger-than-usual earthquake has increased.

The probability of a mega-earthquake occurring along the Japan Trench and the Kuril Trench is estimated to be around 0.1% under normal circumstances. However, past precedents show that if an earthquake equivalent to magnitude 7 occurs globally, the probability of another earthquake exceeding magnitude 8 within a week rises to approximately 1%.

A spokesperson for the Japan Meteorological Agency stated at a press conference this afternoon that "this earthquake occurred within the active zone of the earthquake on the 8th," and urged continued caution against earthquakes in areas that experienced strong shaking during the earthquake on the 8th.

The spokesperson also requested, "Please refrain from entering the sea or approaching the coast until the tsunami advisory is lifted."

However, the agency did not extend the aftershock caution period as the magnitude of this earthquake did not reach 7.0.

Prime Minister Sanae Takaichi stated, "While paying attention to information from the Meteorological Agency and local governments, it is necessary to reconfirm earthquake preparedness measures such as checking safe evacuation sites and routes, and securing furniture." He added, "Please continue social and economic activities while maintaining a state of readiness to evacuate immediately upon sensing shaking."