Are you sure that's a "focused shock wave"? It looks to me like the roof of the building flying upwards (while presumably shattering, so you don't see a large object falling back down again. I'd expect the roof to be lighter and less reinforced than the walls of the building, so more likely to be flung away by the force of the explosion.
By the way, though this has been called a "hydrogen explosion", I'm not convinced that there was any combustion, since I don't see any flames. I think it was just a violent gas release (hydrogen, I guess?), as pressure inside built up too high.