  We construct quasimodes for some non-selfadjoint semiclassical operators at
the boundary of the pseudo-spectrum using propagation of Hagedorn wave-packets.
Assuming that the imaginary part of the principal symbol of the operator is
non-negative and vanishes on certain points of the phase-space satisfying a
subelliptic finite-type condition, we construct quasimodes that concentrate on
these non-damped points. More generally, we apply this technique to construct
quasimodes for non-selfadjoint semiclassical perturbations of the harmonic
oscillator that concentrate on non-damped periodic orbits or invariant tori
satisfying a weak-geometric-control condition
