This is due to their strict building codes and major preventative measures. A quake that big in Los Angeles would cause thousands of buildings to crumble. I was in L.A. during the Northridge quake. The damage was severe and that was a 6.7, or what some of the Japan aftershocks will be. Japan was as prepared as any country could be.
The apocalyptic damage in the northeast of the Japan was from the tsunami. There’s no way to stop a wall of water 30 feet tall. This was a black swan, an utterly unanticipated event which changes everything.