  We present a new method for the detection and characterization of expansion
in galaxy discs based on H{\alpha} Fabry-Perot spectroscopy, taking advantage
of the high spatial and velocity resolution of our instrument (GH{\alpha}FaS).
The method analyses multi-peaked emission line profiles to find expansion along
the line of sight on a point-by-point basis. At this stage we have centred our
attention on the large scale structures of expanding gas associated with HII
regions which show a characteristic pattern of expansion velocities, of order
100 km/s, as a result of both bubble shape and projection effects. We show an
example of the expansion map obtained with our method from a superbubble
detected in the Antennae galaxies. We use the information obtained from the
method to measure the relevant physical parameters of the superbubbles,
including their ages which can be used to date young star clusters.
