That article clearly needs expanding. It's missing the most obvious conclusion of previous discussions. In a FE scenario, a device of this level of precision would have to account for EA; or, in other words, the apparent curvature of the Earth.
As we established in previous discussions, this adjustment was performed predominantly through electromagnetic means. There's no big mystery here.
That said, this thread is not about LIGO, and we do not need a duplicate thread on it. Already, stack is wasting our time by repeating explanations we've already gone through. If you want to continue that discussion, just revive the old thread.