  We show theoretically what is meant by the term '(surface shape) resonance'
in connection with the seismic response of a protuberance (emerging from flat
ground) such as a hill or mountain of arbitrary shape. We address the specific
problem of cylindrical protuberances of rectangular shape submitted to a SH
plane wave. We find that the principal (i.e., qualitative) characteristics of
the seismic response of a mountain are quite similar to those of a hill, and
that the occurrence of significative amplification of the displacement field
within these structures is due to the coupling of the incident wave to (surface
shape) resonances.
