Friday Aftershock

It's Friday afternoon in Chengdu now, the earthquake was Monday afternoon. So almost exactly 4 days later, we just got hit with another aftershock. It lasted maybe 15 seconds and it was small. Quite small but clear, and it probably felt stronger up here on the 17th floor. I really can't imagine this fairly new 19-storey apartment high-rise tumbling down now because it swayed a couple of inches, but it is a little stressful to still be feeling aftershocks days later.
Now be aware that I don't know anything about plate tectonics, but it's still worrisome to think that the aftershocks we feel here must be quite a bit stronger 62 miles away in Wenchuan 汶川, at the epicentre. I had thought that everybody was sleeping back inside by now, since the masses of people crowding out the streets and sidewalks on Monday night have long since dispersed. In talking with friends the past two days, however, it seems there's still a significant number of people here in the city (including a few of my friends) sleeping on sports fields and in the amusement park for fear of strong aftershocks.