I remember after 921 there was talk of 'unlucky' 12 story buildings collapsing. It was later learned that that height allowed for a resonance of the seismic wave to be hit (not sure what the proper term is). The height allowed the wave to be amplified or at least it did not interrupt the wave. It all had to do with physics more so than construction quality. Buildings a floor or two different of the same quality stayed standing.

That's interesting - i always thought it was coz a stricter building-code kicked-in after 12 floors.

But it could be right. Have noticed that mountain ranges slow down earthquakes the same way they do typhoons - they absorb the impact. A big earthquake in the Rift Valley for example will be significantly reduced by the coastal range by the time it gets to Dulan.

Could be like catching a wave - too low it rolls over you - too high it absorbs the impact up, but 12-floors is where you catch the wave - the sweet-spot for blowing the stack.

Wave analogy is not quite right - if you're near the epicentre of a big earthquake, they don't roll through as a swaying wave like they do if you're 100k away, they violently jump.

So if there's a wave of energy, it's going straight up the building.

Which would make the weights on the roof a reasonable hypothesis. Pretty simple to do. Bad news for all those cool quasi-legal roof-top apartments in Taiwan though ...