  Using computer simulations, we show that the localized low frequency normal
modes of a configuration in a supercooled liquid are strongly correlated with
the irreversible structural reorganization of the particles within that
configuration. Establishing this correlation constitutes the identification of
the aspect of a configuration that determines the heterogeneity of the
subsequent motion. We demonstrate that the spatial distribution of the
summation over the soft local modes can persist in spite of particle
reorganization that produces significant changes in individual modes. Along
with spatial localization, the persistent influence of soft modes in particle
relaxation results in anisotropy in the displacements of mobile particles over
the timescale referred to as beta relaxation.
