  Context. Prominence oscillations have been mostly detected using Doppler
velocity, although there are also claimed detections by means of periodic
variations in half-width or line intensity. However, scarce observational
evidence exists about simultaneous detection of oscillations in several
spectral indicators. Aims. Our main aim here is to explore the relationship
between spectral indicators, such as Doppler shift, line intensity, and line
half-width, and the linear perturbations excited in a simple prominence model.
Methods. Our equilibrium background model consists of a bounded, homogeneous
slab, which is permeated by a transverse magnetic field, having prominence-like
physical properties. Assuming linear perturbations, the dispersion relation for
fast and slow modes has been derived, as well as the perturbations for the
different physical quantities. These perturbations have been used as the input
variables in a one-dimensional radiative transfer code, which calculates the
full spectral profile of the hydrogen H-alpha and H-beta lines. Results. We
have found that different oscillatory modes produce spectral indicator
variations in different magnitudes. Detectable variations in the Doppler
velocity were found for the fundamental slow mode only. Substantial variations
in the H-beta line intensity were found for specific modes. Other modes lead to
lower and even undetectable parameter variations. Conclusions. To perform
prominence seismology, analysis of the H-alpha and H-beta spectral line
parameters could be a good tool to detect and identify oscillatory modes.
