What was Thom Mayne's inspiration?

I'm crossposting this from one of my other blogs, Planetizen Interchange, which is an urban planning thing. Because I think it has appeal in this world, too.

The new San Francisco Federal Building, designed by Morphosis 'starchitect' Thom Mayne, opened earlier this year.

And I knew it looked familiar. Today I finally figured it out.

The building:



And what must have been the inspiration:

from wired magazine