A magnitude 7.5 earthquake struck off the eastern coast of Aomori Prefecture, Japan, late at night on the 8th. Japanese experts stated that this is a typical earthquake occurring at a geological plate boundary, and its mechanism is similar to the magnitude 9 Great East Japan Earthquake in 2011.
Japanese experts are generally concerned that, due to the same mechanism, a major earthquake could occur in the Nankai Trough of the Pacific Ocean off eastern Japan in the future.
Kazunari Obara, former president of the Seismological Society of Japan, indicated that this Aomori earthquake is a typical interplate earthquake, triggered by the Pacific Plate on the ocean side subducting beneath the North American Plate on the land side, causing the land-side plate to be unable to withstand the strain and resulting in the earthquake. Earthquakes are categorized as interplate earthquakes occurring at plate boundaries, and intraplate earthquakes caused by fault activities within the plates.
Taku Nishimura, professor at the Disaster Prevention Research Institute of Kyoto University, pointed out that the focus of this earthquake was relatively deep, but its proximity to the land led to intense shaking being observed.
The area near the epicenter of this earthquake experienced major earthquakes in 1968 and 1994, and this area is also a projected seismic source region of the Japan Trench and Kuril Trench, which are closely monitored by the Japanese government.
Ryota Hino, professor at Tohoku University, stated that this earthquake occurred in a seismically active region that has been assessed for a long time by the government, making it an expected event.
He speculates that after the Great East Japan Earthquake, the slow slip movement at the plate boundary may have spread to the area off the coast of Aomori, possibly acting as the "trigger" for this earthquake.
Taku Nishimura also believes that residual faults in the plates that were not completely ruptured during the 1994 magnitude 7.6 earthquake may have slipped. According to past experience, major earthquakes may occur in succession, so vigilance should be maintained in the coming week.
In the early hours of the 9th, the Japan Meteorological Agency and the Cabinet Office issued a "Seismic Activity Advisory for Hokkaido and Sanriku Coast," indicating that experts believe the probability of a major earthquake occurring in the relevant region in about the next week is higher than usual.