  The Newtonian solid-mechanical theory of non-compressional spheroidal and
torsional nodeless elastic vibrations in the homogenous crust model of a
quaking neutron star is developed and applied to the modal classification of
the quasi-periodic oscillations (QPOs) of X-ray luminosity in the aftermath of
giant flares in SGR 1806-20 and SGR 1900+14. Particular attention is given to
the low-frequency QPOs in the data for SGR 1806-20 whose physical origin has
been called into question. Our calculations suggest that unspecified QPOs are
due to nodeless dipole torsional and dipole spheroidal elastic shear
vibrations.
