A novel laboratory technique is proposed to investigate wave-induced
fluid flow on the mesoscopic scale as a mechanism for seismic attenuation
in partially saturated rocks. This technique combines measurements
of seismic attenuation in the frequency range from 1 to 100?Hz with
measurements of transient fluid pressure as a response of a step
stress applied on top of the sample. We used a Berea sandstone sample
partially saturated with water. The laboratory results suggest that
wave-induced fluid flow on the mesoscopic scale is dominant in partially
saturated samples. A 3-D numerical model representing the sample
was used to verify the experimental results. Biot's equations of
consolidation were solved with the finite-element method. Wave-induced
fluid flow on the mesoscopic scale was the only attenuation mechanism
accounted for in the numerical solution. The numerically calculated
transient fluid pressure reproduced the laboratory data. Moreover,
the numerically calculated attenuation, superposed to the frequency-independent
matrix anelasticity, reproduced the attenuation measured in the laboratory
in the partially saturated sample. This experimental?numerical fit
demonstrates that wave-induced fluid flow on the mesoscopic scale
and matrix anelasticity are the dominant mechanisms for seismic attenuation
in partially saturated Berea sandstone.