December 01, 2016
Earthquakes and the JMA
The Japan Meteorological Agency classifies earthquakes in absolute (Richter scale) and relative terms. This provides the public with practical information, especially when the epicenter often isn't directly below the locations most affected (click image for full size).
So the 7.4 magnitude (later revised .1 upward) earthquake the Monday before last rated at worst a "5-" in actual effect ("seismic intensity") on land.
The earthquake struck at 5:59 AM (Japan time). That meant the 6:00 AM news (2:00 PM MST) was immediately interrupted by "earthquake coverage," which follows a pretty standard format.
No talking heads (at first), no reporters babbling into the camera with no idea what is going on. The screen switched to a live feed from Onohama harbor in Iwaki, Fukushima, closest to the epicenter. Pertinent information is relayed via on-screen text or audio.
At 6:02 came a tsunami warning, worst-case at three meters. Not disastrous, but enough to be concerned about.
The audio at this point turned, well, excitable. I imagine the poor guy had just gotten to work and hastily swallowed a liter of coffee. Pretty much: "Flee for your lives!" The red-highlighted text on the screen said the same thing. With explanation points.
Recalling that 16,000 people died from the 2011 Tohoku tsunami, this concern is understandable. (The 7.4 magnitude mainshock this time has since been categorized as an aftershock to the 2011 Tohoku earthquake.)
The fishermen certainly weren't taking any chances. As I said, the live feed was from Onohama harbor. It was fascinating to watch all the fishing boats rev up and head out to sea. In twenty minutes, the harbor was empty. Very impressive.
I do wonder about the "crying wolf" problem.
As it turned out, the deepest tsunami was five feet in one location and was more of a tidal surge. Most everywhere else along the coast, it was a foot to eighteen inches. One small boat capsized and nets drying on the docks got washed into the harbor.
But nobody is questioning the "better safe than sorry" policy, and certainly not in Tohoku.
Along with its early warning system, the JMA provides public data on earthquakes. Whenever NHK flashes a warning, I go to the JMA Earthquake Information site (Japanese/English). As you will see, earthquakes are a fact of life in Japan. (Click on a date in the left-hand column for details.)
As illustrated above, the colored round dots indicate the relative magnitude. Clicking on the map (such as here) lets you zoom in.