Kyushu earthquakes?

[cantunamunch]

I don't really understand the Japanese seismic scale. Thursday's and Friday's shakes were reported at 6.5 which seems pretty durn awful, especially if followed up by torrential rains. NHK is reporting Saturday's quake at 7.3 which seems like the worst possible, actually beyond the top of the scale?

Obviously, since it's NHK they're not *really* going to play up risk - not to Sendai nuclear and not to structures as a result of landslides in the rain.

Anyone have any insight here?

 

[scott43]

Google says Japan uses a relative "shaking" measurement, capped at 7. Richter uses energy released in an exponential scale, relatively impossible to exceed the max. So I suspect the 6.4 and 7.3 are Richter scale measurements and the exceeding 7 is the Japanese measurement?

 

[Jim McDonald]

The Japanese7-level "shindo" scale is an estimate of intensity at a given location, i.e. the practical effect of a quake.
It's completely different from the commonly referenced Richter measure.

https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_seismic_intensity_scale

 

[cantunamunch]

Google says Japan uses a relative "shaking" measurement, capped at 7. Richter uses energy released in an exponential scale, relatively impossible to exceed the max. So I suspect the 6.4 and 7.3 are Richter scale measurements and the exceeding 7 is the Japanese measurement?

USGS is reporting that quake at M7.0 - M for moment magnitude, replacing Richter, which would be about as bad as it gets.

http://earthquake.usgs.gov/earthquakes/eventpage/us20005iis#general

The Japanese7-level "shindo" scale is an estimate of intensity at a given location, i.e. the practical effect of a quake.
It's completely different from the commonly referenced Richter measure.

https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_seismic_intensity_scale

Yes, it is exactly the practical effect I am asking about. What is actually going on? I've seen pics of one landslide and reports of 41 fatalities. That seems rather inconsistent with a practical effect of 'Beyond Worst Possible'. Is it being deliberately toned down or what?

 

[Jim McDonald]

USGS has changed their reporting format, etc. I'm sure the new data improves accuracy in scientific terms, but it's rather less user-friendly.
The Japanese scale essentially comes down to someone at a specific place saying: hmmm, that knocked me on my ass; must've been a 7. Meanwhile somebody a few km away judges it as a 5, since a few knickknacks got knocked off the mantle.
The shindo 7 on this Kyushu quake is an intensity rating in one small town; you can't really extrapolate from that.