  Recently, it has been shown that with the inclusion of overtones, the
post-merger gravitational waveform at infinity of a binary black hole system is
well-modelled using pure linear theory. However, given that a binary black hole
merger is expected to be highly non-linear, where do these non-linearities,
which do not make it out to infinity, go? We visualize quantities measuring
non-linearity in the strong-field region of a numerical relativity binary black
hole merger in order to begin to answer this question.
