  Measurements of the surface velocity and surface texture of a freely
propagating shear jamming front in a dense suspension are compared. The
velocity fields are captured with particle image velocimetry (PIV), while the
surface texture is captured in a separated experiment by observing a direct
reflection on the suspension surface with high-speed cameras. A method for
quantifying the surface features and their orientation is presented based on
the fast Fourier transform of localised windows. The region that exhibits
strong surface features corresponds to the the solid-like jammed region
identified via the PIV measurements. Moreover, the surface features within the
jammed region are predominantly oriented in the same direction as the
eigenvectors of the strain tensor. Thus, from images of the free surface, our
analysis is able to show that the surface texture contains information on the
principle strain directions and the propagation of the jamming front.
