https://share.sandia.gov/news/resources/releases/2007/astero...
Most descriptions speak of a single explosion, something comparable to a nuclear weapon. That isn't an appropriate model. It wasn't a single event at a fixed spot, nor was it a series of events. It was more of a continuous release of energy over a great distance. The rock exploded not at a particular altitude, but dissipated its energy into the atmosphere over a period of time/distance, a line rather than a point. Square-area/volume principals therefore do not apply directly. With that understanding it turns out it was probably a much smaller rock than previously though.
The trees were not knocked over all at once. I think of it more as them being blown down in series as if by the wake of a passing boat, that boat being an exploding rock. So you cannot take the total damage area and calculate a single point for the explosion.
Old model: http://www.sandia.gov/videos2007/2007-6514Pfire.hv1.2.mpg
New model: http://www.sandia.gov/videos2007/2007-6514Pfire.hv1.1.mpg