I'm on a bus with a bunch of people. There's a big explosion, which we apparently expected, because we are wearing helmets. It blows out the windows of the bus and scatters debris everywhere.

Another explosion is coming imminently, and my helmet (my green one from mountain climbing days) is on the ground among some debris. I'm trying to grab it really fast before the explosion - it definitely seems necessary, the flying debris could kill you. I don't have time to fasten it but I hold it on my head; I think that's protection enough.

(I saw a video that day showing a big wave bursting through the front door of a restaurant, rather similar)