I just (15:18 on 8 October '08, JST) experienced a brief, mild earthquake.
It was strong enough to be noticeable, but not to trigger the automatic shutdown of my office building's elevators and its attendant PA announcement to the effect that an earthquake shut the elevators down and if you need to evacuate, you take the stairs. It's a relatively small building, so the announcement is pretty much superfluous: the single flight of stairs is within a few meters of the single elevator hall with its two elevators, so if you see that the elevators aren't running, you don't have far to go or much in the way of options if you want to leave the building.
I'm never in a hurry to leave a building in an earthquake. There's a lot of stuff out there that can be shaken down on passersby including roof tiles, hanging signs, window glass, etc., and in a recent major earthquake the very first victim was a guy who ran out of his shop into the street and was hit by a passing truck. Most of the buildings I spend much time in here in the Kanto Plains area are reasonably robust, and there's usually a desk or sturdy table under which I can take shelter if I really think it's necessary. I'll leave once the shaking's over, if it seems to be indicated (like, say, if the building's collapsing or on fire) but otherwise I figure I'm better off inside.
On the other hand, I believe that the land my office building stands on is landfill from a couple of hundred years ago: old maps show the beach across the (major thoroughfare) street from us, so this used to be tidal flats. It might just temporarily liquefy, in a really big quake. Of course, in a quake that strong, the building will probably collapse around my ears and the problem will become academic.
I'm reminded that I need to replenish my office emergency supplies. I used to keep a couple of days' worth of food and water, and some extra clothes and heavy boots, and some basic tools and utensils to use if I have to get along for a couple of days in a really devastated Tokyo before emergency services--if any--kick in. I've still got most of the stuff, but the food and water were used up and not replaced as they got close to their use by dates. It's time to go shopping for more.
I was impressed by the speed with which the Japan Meteorological Agency got the news on their website; within just a couple of minutes the updated map and numbers were there. Of course, if you visit them, it's very likely that the latest earthquake will be another one, since they're pretty frequent here.
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