Can a million tonnes of building debris arrive at ground level from 100 stories above without producing a large seismic signal ... And not damage the dyke holding out the Hudson River, and not even collapse the several stories below ground level?
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The answer to that question probably depends on the foundation design of the building.
IOW, the siesmic event could have been disguised considerably at the surface, depending on conditions.
We do know from the available video that the debris was in freefall for the entire time that it was visible to the cameras. That is a bunch of energy to dissipate!
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