  The orientation and deformation of moving vortex lattices in the flux-flow
state have been investigated in amorphous superconducting NbGe thin films.
Employing a mode-locking technique, we detect how moving lattices deform and
their orientation changes as a magnetic field is tilted from normal to the film
surface. For high tilt angles the lattice orientation is aligned parallely with
the tilt direction. Meanwhile for low tilt angles the lattice orientation
depends on the vortex velocity and a velocity-induced reorientation occurs. The
characteristic velocity for the reorientation varies remarkably as the moving
lattices deform. The observed features are consistent with an extended
bond-fluctuation theory, revealing that the anisotropic shaking vortex motion
is essential for determining the orientation of moving vortex lattices.
