7.3 earthquake near Fukushima in Japan | Hacker News Reader

7.3 earthquake near Fukushima in Japan

nbcnews.com

107 pointsasimjalis12 comments

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Japan Meteorological Agency reported it as 7.1

USGS reported it as 7.1

Prime Minister Suga reported "no anomalies, ... everything is normal."

Okay. The Japanese have a lot of experience with earthquakes. They should know. I trust the assessment.

The article declares it 7.3, citing the JMA, who were quoted as reporting it as 7.1 in the very next paragraph.

No explanation anywhere for how it became 7.3.

Meh, what's two points on a logarithmic scale of seismic energy?

No conspiracy. When I first calmed down after I felt the shaking I checked the JMA website and it was reported as a 7.3. Later downgraded to 7.1. This happens all the time

NHK is reporting power and gas outages, a landslide on a highway and minor infrastructure damage, but nothing severe. No nuclear plants are reporting anomalies, and there's no risk of tsunami.

https://www3.nhk.or.jp/nhkworld/en/news/20210214_29/

(Edit: this is the english-language NHK and doesn't go into everything I said...I'm watching the coverage on Japanese TV, which is more detailed.)

https://earthquake.usgs.gov/earthquakes/eventpage/us6000dher...

> 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

I always assumed those plates moved less than 5mm/year. It's almost a yard each decade.

Luckily though, it seems to have been so deep (50km) that the surface effects were not as bad as could be for a 7.3.

The concern some have is that this earthquake could simply be the lead in for the larger one to follow similar to the Tohoku quake

There have been 9 earthquakes in this region of magnitude >= 7.0 since 2011, including the 9.1 Tohoku quake. Of the remaining magnitude >= 7 quakes, 5 were in 2011, 1 was in 2012, and 1 in 2013, and finally the newest one yesterday.

Source:

https://earthquake.usgs.gov/earthquakes/map/?extent=16.46769...

That's helpful information. It doesn't invalidate the concern, however, since very large earthquakes are often preceded by moderately large foreshocks, so there is an now a temporarily elevated risk of a very large earthquake in that region.

In the list you can see a foreshock happening two days before 9.1 earthquake (Tohoku). Then after that you have a couple of years of aftershocks. Obviously this is not a guarantee "big one" is coming but it's probably good idea to check contingency plans.

I was in a tenth-floor restaurant in central Tokyo during that March 9, 2011, earthquake, two days before the big one. The shaking last night, which I felt at my home in Yokohama, was reminiscent: not terribly strong, but lasting a long time.

Last night, it was long enough for me to sit up in bed, wait for a while, get up, stand in the living room for a while, and then go upstairs to where my daughter and one-year-old grandson were sleeping, with the shaking and rattling continuing the whole time. After it stopped, we all went back to bed.

In 2011, I happened to leave Yokohama for Osaka by train on the morning of March 11 and missed the big one by just a few hours. I'm hoping to be away when the next big one hits, too.

This one is being called an aftershock of the 2011 large earthquake. Not sure if that makes much difference in what happens next, though...

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