A magnitude 6.9 earthquake has struck near Iwate Pref Japan

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quiet35•1 day ago

6.9 is an intensity on a Japan Meteorological Agency Seismic Intensity Scale, which can vary from 0 to 7. So it's the second strongest intensity possible on the scale. https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_se...

zamadatix•1 day ago

It's just a "6+" on the Japan Meteorological Agency seismic intensity scale, which does otherwise fit the description about being 1 less than the maximum on that scale, but the "M 6.9" actually refers to the value in the more universal moment magnitude scale (and just happens to also start with 6 in this case). When intensity is mentioned it's the 0-7 scale, when M or magnitude is mentioned it's about the moment magnitude scale.

https://earthquake.usgs.gov/earthquakes/eventpage/us6000t7zq...

qmarchi•1 day ago

You're conflating two things, magnitude and intensity.

This earthquake was measured as a 6.9 moment magnitude, sometimes referred to incorrectly as the "Richter" scale.

The Shindo intensity system is measured without decimal places. In this particular case, the intensity was a 6+. Which isn't the highest, but is still quite severe.

mc3301•1 day ago

And the Shindo system is best described as "what it feels like at the specific location"

So an earthquake can be a 4 at the epicenter, a 3 a little further away, a 2 even further away, and so on.

Common online conversation with a friend in a different prefecture may be something like, "Last night's earthquake was a 3 here, how about you?"

circumlocution•1 day ago

I'm in Tokyo and was awoken by the quake hitting here at 7:33; you can really feel the building sway on higher floors

A magnitude 6.9 earthquake has struck near Iwate Pref Japan

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Discussion (5 Comments)Read Original on HackerNews