Top shelf seismometer

The USGS has the 'Did You Feel It?' website for generating shake maps for earthquakes felt by anybody. Late last night, I felt the modest 3.2 quake in Oakland.

I may have been the only one in San Francisco to feel it (they don't show locations on the map under a certain number of entries, apparently). Why did I feel it and nobody else in SF? Well, it was after midnight, and it was rather late (after midnight). And, it wasn't a very strong earthquake either.

But, another reason is the bookshelf-liquor bottle seismometer we have in our apartment. On the top shelf of said bookshelf we keep the handful of bottles of liquor we have. When the bus goes by our apartment, they rattle ever so slightly. Something about the slightly warped hardwood floor in this 1940s building makes this set-up a very sensitive recorder of any motion. Last night as I was working late, the bottles rattled, but a lot slower than when the bus goes by. Earthquake! The fact that no bus was going by at that moment was another clue.