  We present a numerical simulation of the response of an expanding
relativistic jet to the ejection of a superluminal component. The simulation
has been performed with a relativistic time-dependent hydrodynamical code from
which simulated radio maps are computed by integrating the transfer equations
for synchrotron radiation. The interaction of the superluminal component with
the underlying jet results in the formation of multiple conical shocks behind
the main perturbation. These trailing components can be easily distinguished
because they appear to be released from the primary superluminal component,
instead of being ejected from the core. Their oblique nature should also result
in distinct polarization properties. Those appearing closer to the core show
small apparent motions and a very slow secular decrease in brightness, and
could be identified as stationary components. Those appearing farther
downstream are weaker and can reach superluminal apparent motions. The
existence of these trailing components indicates that not all observed
components necessarily represent major perturbations at the jet inlet; rather,
multiple emission components can be generated by a single disturbance in the
jet. While the superluminal component associated with the primary perturbation
exhibits a rather stable pattern speed, trailing components have velocities
that increase with distance from the core but move at less than the jet speed.
The trailing components exhibit motion and structure consistent with the
triggering of pinch modes by the superluminal component.
