Centurion- it felt like far longer than a minute!

2nd floor media centre in a primary school. Once I realised what was happening I walked from the media office to the corridor to see if I could see any signs of an explosion. Back in to find a worried class with one child crying. Launched into calming children by touching on earthquakes in danger zones near edges of plates and that we are not anywhere near the edge of a plate and so will be fine. All the while the vertical blinds are vibrating madly! Then I talked a bit about collapsing mines etc. which we would feel but are nowhere near us. The children calmed and I walked back to the office. Surely that took more than a minute!