Mag 7.6 - 73 km ENE of Misawa, Japan, tsunami warning issued

[Astronuc]

M 7.6 - 73 km ENE of Misawa, Japan​

https://earthquake.usgs.gov/earthquakes/eventpage/us6000rtdt/executive

• 2025-12-08 14:15:11 (UTC)
• 40.960°N 142.185°E
• 53.1 km depth

It was however fairly deep (53.1 km depth) as compared to the Great Tohoku earthquake in which the sea floor was displaced. I don't believe a tsunami would be significant.

Seismotectonics of Japan and Vicinity​

The North America plate, Pacific plate, Philippine Sea plate, and Eurasia plate all influence the tectonic setting of Japan, Taiwan, and the surrounding area. Some authors divide the edges of these plates into several microplates that together take up the overall relative motions between the larger tectonic blocks, including the Okhotsk microplate in northern Japan, the Okinawa microplate in southern Japan, the Yangzee microplate in the area of the East China Sea, and the Amur microplate in the area of the Sea of Japan.

The seafloor expression of the boundary between the Pacific and North America plates lies 300 km off the east coasts of Hokkaido and Honshu at the Kuril-Kamchatka and Japan trenches. The subduction of the Pacific plate beneath the North America plate, at rates of 83-90 mm/yr, generates abundant seismicity, predominantly as a result of interplate slip along the interface between the plates. The 1958 M 8.4 Etorofu, 1963 M 8.6 Kuril, 2003 M 8.3 Tokachi-Oki, and the 2011 M 9.0 Tohoku earthquakes all exemplify such megathrust seismicity. The 1933 M 8.4 Sanriku-Oki earthquake and the 1994 M 8.3 Shikotan earthquake are examples of intraplate seismicity, caused by deformation within the lithosphere of the subducting Pacific plate (Sanriku-Oki) and of the overriding North America plate (Shikotan), respectively.

At the southern terminus of the Japan Trench the intersection of the Pacific, North America, and Philippine Sea plates forms the Boso Triple Junction, the only example of a trench-trench-trench intersection in the world. South of the triple junction the Pacific plate subducts beneath the Philippine Sea plate at the Izu-Ogasawara trench, at rates of 45-56 mm/yr. This margin is noteworthy because of the steep dip of the subducting Pacific plate (70° or greater below depths of 50 km depth), and because of its heterogeneous seismicity; few earthquakes above M 7 occur at shallow depths, yet many occur below 400 km. The lack of large shallow megathrust earthquakes may be a result of weak coupling at the plate interface, or simply a reflection of an incomplete earthquake catalog with respect to the length of typical seismic cycles.

https://earthquake.usgs.gov/earthquakes/eventpage/us6000rtdt/region-info

 

[Astronuc]

Some surveillance vidoes of the earthquake response in Amori prefecture, Japan.

 

[Astronuc]

One strong aftershock

M 6.6 - 126 km S of Honchō, Japan; 205.2 km (127.5 mi) E of Amori, Amori, Japan​

https://earthquake.usgs.gov/earthquakes/eventpage/us6000rtie/executive

• 2025-12-08 21:52:41 (UTC)
• 41.003°N 143.164°E
• 19.0 km depth

Other aftershocks were in the range of 4.4 to 5.8 Mag.

 

[davenn]

M 7.6 - 73 km ENE of Misawa, Japan​

https://earthquake.usgs.gov/earthquakes/eventpage/us6000rtdt/executive

• 2025-12-08 14:15:11 (UTC)
• 40.960°N 142.185°E
• 53.1 km depth

Am late posting again haha

M7.6 Japan quake on my seismo (Sydney, Australia) this morning
The location for this event is a long way north of the previous large events in the region and I would be confident in saying that it is well outside the aftershock zone of those events

updated info.....

M 7.6 - 2025 Aomori Prefecture, Japan Earthquake​

• • 2025-12-08 14:15:10 (UTC)
  • 41.043°N 142.141°E
  • 44.1 km depth
  
  
  
  
  

 

[davenn]

Another strong aftershock just tailed off on my seismo

M 6.7 - 114 km ENE of Hachinohe, Japan​

• 2025-12-12 02:44:11 (UTC)
• 40.918°N 142.745°E
• 10.7 km depth

 

[davenn]

This has been a significant quake and not directly related to the Mw9.1 megathrust quake that occurred on 11 March 2011 at 05:46 UTC which has produced some significant aftershocks since 2011, particularly during the 2021 - 2022 period when many M6+ to M7+ events occurred within the aftershock zone.

I would like to suggest that this latest series of quakes, that include the 3 largest ones of Mw7.6, 6.6 and 6.7 appear to be far enough north of the aftershock zone of the Mw9.1 to produce a distinctly separate series
of events.
The only direct relationship would be that they are all on the subduction zone of the Japan Trench.
A possible indirect relationship could be the change in stress fields along the subduction zone as a
result of the Mw9.1 event. This is generally most easily observable at either end of a rupture zone.

These are thrust events, typical of subduction zones and moment tensor solutions as shown below...

cheers
Dave