7.3 Magnitude Quake Hits North Japan

[gmax137]

TL;DR Summary

7.3 Magnitude Quake Hits North Japan, Tsunami Alert Issued

https://www.bloomberg.com/news/arti...e-quake-hits-north-japan-tsunami-alert-issued

 

[berkeman]

Yikes. That's not good...

Although, if it really is only 1 meter above normal tidal levels, that's a lot less than the previous one, right?

https://www.cnn.com/2022/03/16/asia/japan-earthquake-fukushima-intl/index.html

The tsunami advisory was made for Fukushima and Miyagi prefectures in eastern Japan following the quake that had a preliminary epicenter depth of 60 kilometers (37 miles), according to the Japan Meteorological Agency.

The advisory warns of tsunami heights reaching up to 1 meter above normal tidal levels, with the initial waves reaching shore around midnight local time (11 a.m. ET).

 

[Astronuc]

M 7.3 - 57 km ENE of Namie, Japan​

https://earthquake.usgs.gov/earthquakes/eventpage/us6000h519/executive

• 2022-03-16 14:36:33 (UTC)
• 37.702°N 141.587°E
• 63.1 km depth

The Mag 7.3 was preceded by a Mag 6.4 earthquake occurring only 2 minutes before and slightly shallower.

M 6.4 - 62 km ENE of Namie, Japan​

https://earthquake.usgs.gov/earthquakes/eventpage/us6000h518/executive

• 2022-03-16 14:34:27 (UTC)
• 37.633°N 141.685°E
• 56.3 km depth

An aftershock

M 5.5 - 77 km SE of Ishinomaki, Japan​

https://earthquake.usgs.gov/earthquakes/eventpage/us6000h518/executive

• 2022-03-16 15:52:31 (UTC)
• 37.853°N 141.827°E
• 67.2 km depth (slightly deeper than the Mag 7.3)

 

[Baluncore]

Those earthquakes are very deep.
Maybe they are aftershocks of the big tsunami earthquake.

 

[Astronuc]

Those earthquakes are very deep.
Maybe they are aftershocks of the big tsunami earthquake.

I would consider that a moderate depth, but perhaps enough to mitigate a tsunami. Of course, it all depends on how and how much of the ocean floor and volume of ocean water is displaced.

In contrast, the 9.1/9.2 Mag Great Tohoku earthquake of 2011 was at a depth of 29 km.
https://earthquake.usgs.gov/earthquakes/eventpage/official20110311054624120_30/executive

M 9.1 - 2011 Great Tohoku Earthquake, Japan​

• 2011-03-11 05:46:24 (UTC)
• 38.297°N 142.373°E
• 29.0 km depth

Rather than aftershocks, the current quakes are simply part of the ongoing seismic activity induced by the flow of the seafloor under crust of which Japan is a part, i.e., subduction of the western edge of the Pacific Plate under the Okhotsk Plate.
https://en.wikipedia.org/wiki/Japan_Trench#Seismicity
https://en.wikipedia.org/wiki/Okhotsk_Plate
https://earthquake.usgs.gov/earthquakes/eventpage/official20110311054624120_30/dyfi/intensity