An important characteristic of fractured rocks is their very high
seismic attenuation, which so far has been assumed to be mainly produced
by wave-induced fluid flow between the fractures and the embedding
matrix. As this fluid pressure equilibration process is strongly
controlled by the hydraulic properties of the heterogeneous rock
sample, the resulting seismic attenuation must also be expected to
contain information about fracture connectivity. To date, however,
the importance of fracture connectivity with regard to the observed
seismic attenuation is largely unknown. Using numerical oscillatory
compressibility simulations based on Biot's quasi-static poroelastic
equations we show that an important, and as of yet non-documented
manifestation of wave-induced fluid flow arises in the presence of
fracture connectivity. We demonstrate that this additional energy
loss is mainly due to fluid flow within the fractures and operates
only in the presence of connected fractures. We also show that this
phenomenon is sensitive to the lengths, permeabilities, and intersection
angles of the fractures. Correspondingly, it contains key information
on the governing hydraulic properties of fractured rocks and hence
should be accounted for whenever realistic seismic models of such
media are needed.