Earthquakes in Japan (Part Infinity)
Earthquakes centered in Tochigi Prefecture a few hours ago: estimated 6.7 M on the modified Richter scale, and a weak 5 on the JMA scale (which measures surface vibrations) in parts of Tochigi and Ibaraki. According to my buddy, they were perceptible in Tokyo. I haven’t seen any reports of damage, but a weak 5, while not as bad as things could be, can cause real problems in craggy, cliffy rural areas with a lot of elderly people. There’s an English translation of the JMA scale here. A weak 5 isn’t strong enough to knock down buildings that are up to code in areas that are prepared for earthquakes, but it’s strong enough to be scary and make it difficult to move.
Oh, yeah, you definitely can feel an earthquake that’s a 6.7 on the Richter scale. I think that was the rating on the earthquake I experienced in Pasadena the summer of 1991. It was 6 point something. :-p It shattered the glass windows of the natatorium into the pool. And, I know some tiles on a roof were damaged. I was in bed, it happened in the morning, and was awakened by the building moving. It was like a bulldozer had run into the building. Then, it dawned on me what was happening…By the time I got to the doorway to stand under it, the tremors had stopped. (And, yes, Sean, I was on the former Ambassador College campus/headquarters of the WCG, doing the college staff SEP thing). The biggest change I noticed was that after the earthquake, the orange haze that hung in the air every day cleared, and I actually saw the mountains that, because of the smog, had become a myth.
An earthquake of magnitude 6.7 releases a certain (large) amount of energy, so of course you’re right that it can be perceptible. Lethal, actually. But like a lot of earthquakes in Japan, this one had a focus that was 40 kilometers below the surface, meaning that the shaking on the ground was quite a bit less intense than it might have been. Things still fell down and stuff in Tokyo, however, according to my friends.