Well, it was not fun on 19th floor on a reclaimed land...
here is more info on quakes
Japan Meteorological Agency | Earthquake Information
Some of those 1000 quakes that took place from the 11th were aftershocks, whereas others were separate earthquakes. Usually, after a huge quake there is a possibility of following earthquakes of slightly lower magnitute. This one today was I think a follow up. It happened close to the 9.0 quake's epicentre, and recent quakes were "walking" around Tokyo. There is a great chance of a quake in Tokyo this year (7+) and possibly Fuji going off. If that happens, Tokyo could be covered in 1m + of ash.