"Run Away" Repeated in Emergency Alert... Magnitude 7.5 Quake Triggers First-Ever Aftershock Warning

Magnitude 7.5 Earthquake Strikes Off Aomori Coast
"Tsunami Warning, Evacuate Immediately"
Tsunami Up to 70cm Observed in Some Areas
At Least 13 Injured, Residential Damage Reported
Meteorological Agency Issues Aftershock Advisory

"Tsunami, run away" "Evacuate to higher ground immediately"

At 11:15 p.m. on December 8, a powerful earthquake with an estimated magnitude of 7.5 struck off the northeastern tip of Honshu, near Aomori Prefecture, Japan, resulting in at least 13 people being injured and causing widespread damage. As tsunami warnings were issued following the earthquake, NHK repeatedly broadcast an emergency alert saying "Tsunami, run away," and the anchor urged viewers multiple times to "Evacuate to higher ground immediately."

House damaged by fire caused by earthquake in Aomori Prefecture. Photo by Yonhap News

At a meeting held at 3 a.m. on December 9, Jiro Akama, Minister for Disaster Management, announced that a total of 13 people had been injured-one seriously, eight with minor injuries, and four with injuries of unknown severity-and that one residential fire had been confirmed. Dozens of reports were also received regarding damaged building walls and sagging power lines. However, it is expected that the scale of the damage could increase further as the situation is assessed in daylight.

On the 8th, a magnitude 7.5 earthquake occurred in Aomori Prefecture, Honshu, Japan, and tsunami warnings were issued for some areas, as reported on Japanese TV. Photo by AP Yonhap News

First 'Seismic Intensity 6 Upper'... "Shaking so strong you can't stand"

In Hachinohe City, Aomori Prefecture, near the epicenter, a seismic intensity of 6 upper was recorded, while Oirase Town and Hashikami Town experienced a seismic intensity of 6 lower. During the Noto earthquake, a seismic intensity of 7 was observed. The Asahi Shimbun reported, "This is the first time since the installation of observation equipment in October 1996 that a seismic intensity of 6 upper has been recorded in Aomori Prefecture."

Unlike magnitude, which indicates the absolute strength of an earthquake, Japan's seismic intensity scale is a relative measure that reflects how people in the affected area feel and the degree of shaking of surrounding objects. When a seismic intensity of 6 upper is observed, people cannot remain standing, and most unsecured furniture will move or topple over. At a seismic intensity of 6 lower, window glass or wall tiles may break.

A magnitude 7.5 earthquake occurred off the coast of Aomori Prefecture, Japan. Japan Meteorological Agency website

Due to this earthquake, tsunami warnings were temporarily issued for the Pacific coastal regions of Honshu's Aomori Prefecture, Iwate Prefecture, and Hokkaido. In response to the tsunami warning, Hachinohe City in Aomori Prefecture ordered evacuations in coastal areas and opened 23 evacuation centers throughout the city.

As of around 1 a.m. on December 9, the observed tsunami heights were 70 cm at Kuji Port in Iwate Prefecture, 50 cm at Urakawa Town in Hokkaido, and 40 cm at Mutsuogawara Port in Aomori Prefecture. At 2:45 a.m. on December 9, all tsunami warnings were downgraded to tsunami advisories. In Japan, a tsunami warning is issued when a tsunami is expected to exceed 1 meter but be less than or equal to 3 meters in height, while a tsunami advisory is issued when a tsunami is expected to be between 0.2 and 1 meter high.

Japan Meteorological Agency issues first 'aftershock warning'

The Japan Meteorological Agency issued its first "aftershock warning for the offshore areas of Hokkaido and Sanriku" at 2 a.m. on December 9 in connection with this earthquake. Introduced in December 2022, this advisory is issued when an earthquake of magnitude 7.0 or higher occurs in regions along the Japan Trench or Kuril Trench, where a major earthquake is expected, indicating that the likelihood of a massive earthquake has increased compared to normal.

Regarding this, an official from the Meteorological Agency explained, "This means the likelihood of a large earthquake has become relatively higher than usual, but it does not guarantee that an earthquake will occur." In March 2011, two days before the Great East Japan Earthquake (magnitude 9.0) struck the offshore areas of Hokkaido and Sanriku, a magnitude 7.3 earthquake had also occurred.