surprising observation can be explained as follows. When both pores and fractures are filled with liquids, the compression caused by the wave will compress the fractures to much greater extent than the background porous material (since fractures are much more compliant than pores), causing the fluid to flow from fractures into pores. Conversely, when the pores are saturated with a liquid and the fractures are dry (or filled with very compressible gas), the compression will cause the flow from pores into fractures (it will be easier to compress gas than deform the fractures). Thus, at some intermediate value of the fluid compressibility (or parameter B), there will be no flow at all, and hence no dispersion or attenuation. (a) (b) Figure 1. Frequency dependency of P-wave velocity (a) and inverse quality factor ܳି ଵ (b) computed using our approximation (17) and Norris model (1) for different values of the parameter B. 10 -3 10 -1 10 1 10 3 10 5 3700 3800 3900 4000 4100 4200 4300 4400 Normalized Frequency P-wave speed(m/s) B=0.001 B=0.01 B=0.1 B=1 B=10 B=100 B=1000 10 -3 10 -1 10 1 10 3 10 5 10 -4 10 -3 10 -2 10 -1 Normalized Frequency Attenuation (1/Q)
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