JF Ptak Science Books Quick Post Part of the History of Holes series
I'm more interested in how this hole was dug and how it got filled up again than in what is filling it. I estimate the "filled" aspect of this reverse-and-inside-out-upside-down monastery to be about 25,000,000 cubic feet, or about two-thirds of the volume of the Empire State Building (which was just being constructed when this article was published). The 40-storey building would about 500' low, and the surrounding supporting structures seem to make the whole of it at least 75' in diameter--finished. That makes for a big hole in the digging of the thing, substantially multiples the volume of the Empire State Building removed in order to achieve the construction needs. That is a lot of dirt.
And so how do we remove the dirt/rock from the 450' level of a 75'-wide hole in 1931? I doubt that it is being hauled out by crane systems, and the hole is certainly wider than 75' at the bottom. I guess these questions could only be answered with the information on what the material is that these folks would be working with. But suffice to say--it would be a big project.
Also: I don't know why this structure would be "earthquake proof", though that is the impetus behind the construction of this monster--the Japanese architects who dreamed this building still had the 140,000 deaths of the 1923 Great Kantō earthquake fresh in their minds. The building looks like it has the capacity to sustain major damage in an earthquake, making it perhaps a flaming and inescapable tomb. It would certainly make a neat if not inexpensive cemetery.
[Image source: Popular Mechanics, 1931, from the great Modern Mechanix site--http://blog.modernmechanix.com/depthscrapers-defy-earthquakes/]