There is increasing evidence to suggest that the presence of mesoscopic
heterogeneities constitutes an important seismic attenuation mechanism
in porous rocks. As a consequence, centimetre-scale perturbations
of the rock physical properties should be taken into account for
seismic modelling whenever detailed and accurate responses of specific
target structures are desired, which is, however, computationally
prohibitive. A convenient way to circumvent this problem is to use
an upscaling procedure to replace each of the heterogeneous porous
media composing the geological model by corresponding equivalent
visco-elastic solids and to solve the visco-elastic equations of
motion for the inferred equivalent model. While the overall qualitative
validity of this procedure is well established, there are as of yet
no quantitative analyses regarding the equivalence of the seismograms
resulting from the original poro-elastic and the corresponding upscaled
visco-elastic models. To address this issue, we compare poro-elastic
and visco-elastic solutions for a range of marine-type models of
increasing complexity. We found that despite the identical dispersion
and attenuation behaviour of the heterogeneous poro-elastic and the
equivalent visco-elastic media, the seismograms may differ substantially
due to diverging boundary conditions, where there exist additional
options for the poro-elastic case. In particular, we observe that
at the fluid/porous-solid interface, the poro- and visco-elastic
seismograms agree for closed-pore boundary conditions, but differ
significantly for open-pore boundary conditions. This is an important
result which has potentially far-reaching implications for wave-equation-based
algorithms in exploration geophysics involving fluid/porous-solid
interfaces, such as, for example, wavefield decomposition.