  The computation of long wave propagation through the ocean obviously depends
on the initial condition. When the waves are generated by a moving bottom, a
traditional approach consists in translating the ``frozen'' sea bed deformation
to the free surface and propagating it. The present study shows the differences
between the classical approach (passive generation) and the active generation
where the bottom motion is included. The analytical solutions presented here
exhibit some of the drawbacks of passive generation. The linearized solutions
seem to be sufficient to consider the generation of water waves by a moving
bottom.
