Earthqaukes in Japan Part 2

The first part of this series can be found here.

The Richter scale versus the Shindo scale

It may not be common knowledge in the West but Japan uses an entirely different scale to compliment the Ritcher scale. The Ritcher scale is based on physics and the measurement of momentum, while the Japanese "Shindo" scale is more functional, categorizing an earthquake's effects on a scale of 1-7. The Japanese scale is also useful for discribing seismic effects for any given area as an earthquake's effect lessen as distance from the epicenter increases. The Ritcher scale does not function this way.

Living as I have now for years in Japan, I have have experienced many earthquakes. Each of them is novel to me because I am a country hick, where such events fill my tiny brain with wonder and curiosity. If a small one does hit, I am normally the guy quickly on my feet afterward looking concerned, where as my coworkers just keep their heads down working.


Japan is as seismicly active as a country can be, and as I mentioned in part one, one of the most active areas is eastern Hokkaido. This is because the Pacific plate is pushing into the North American plate (on which Hokkaido sits). Japan unfortunately sits upon four different plates, thus, in someways Japan is lucky if the quake is only 7 on the Ritcher scale as this configuration of plates harbors the potential for much bigger quakes.

There are several different types of quakes. One is a sudden, sharp type movement due to a different type of energy wave propagation through the ground that I have never experienced. Most quakes I have experienced are under 3. They are characterized by a slow crescendo of movement building up and then tapering away. I have always associated them with a sound; like a deep bass tone from a sub-woofer, but the sound of an earthquake has never been recorded to my knowledge. The two biggest I remember just kept building and building and I didn't know at what point I was suppose to get under the kitchen table; after the dishes start rattling or after the windows start to rattling or after the walls start creaking?

When I stop to think about the power involved in earthquakes it's quite startling. That something hundreds of kilometers away could cause my house to move so easily is sobering.


(Click to enlarge. The image is fine, the thumbnail is just screwed up. Notice how dark Japan is covered. Thanks for the pics Wikipedia!)