  The sensitivity of aLIGO detectors is adversely affected by the presence of
noise caused by light scattering. Low frequency seismic disturbances can create
higher frequency scattering noise adversely impacting the frequency band in
which we detect gravitational waves. In this paper, we analyze instances of a
type of scattered light noise we call "Fast Scatter" that is produced by motion
at frequencies greater than 1 Hz, to locate surfaces in the detector that may
be responsible for the noise. We model the phase noise to better understand the
relationship between increases in seismic noise near the site and the resulting
Fast Scatter observed. We find that mechanical damping of the Arm Cavity
Baffles (ACBs) led to a significant reduction of this noise in recent data. For
a similar degree of seismic motion in the 1-3 Hz range, the rate of noise
transients is reduced by a factor of ~ 50.
