  The numerical simulations of an ultrashort pulse propagation in a
one-dimensional nonlinear photonic crystal are carried out. It is known that
the relaxation of cubic nonlinearity is the reason for the effect of pulse
self-trapping in such multilayer system. In this paper we study further
implications of this effect. It is shown that the trapped light absorbs
additional low-intensity pulses which cannot be self-trapped \textit{per se}.
On the other hand, such low-intensity pulses are subject of the so-called
induced trapping when light gets trapped due to a collision of two such pulses.
We consider the conditions for this effect in both cases of co- and
counter-propagating pulses.
