Seismic attenuation due to wave‐induced flow

Abstract

[1] Three P wave attenuation models for sedimentary rocks are given a unified theoretical treatment. Two of the models concern wave-induced flow due to heterogeneity in the elastic moduli at ''mesoscopic'' scales (scales greater than grain sizes but smaller than wavelengths). In the first model, the heterogeneity is due to lithological variations (e.g., mixtures of sands and clays) with a single fluid saturating all the pores. In the second model, a single uniform lithology is saturated in mesoscopic ''patches'' by two immiscible fluids (e.g., air and water). In the third model, the heterogeneity is at ''microscopic'' grain scales (broken grain contacts and/or microcracks in the grains), and the associated fluid response corresponds to ''squirt flow.'' The model of squirt flow derived here reduces to proper limits as any of the fluid bulk modulus, crack porosity, and/or frequency is reduced to zero. It is shown that squirt flow is incapable of explaining the measured level of loss (10 À2 < Q À1 < 10 À1 ) within the seismic band of frequencies (1-10 4 Hz); however, either of the two mesoscopic scale models easily produces enough attenuation to explain the field data.

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“…In order to be complete, one should also mention the research effort ©S.Hirzel Verlag · EAA in the domain of geophysics which has recently produced anumber of inspiring papers, e.g. [8,9,10,11].…”

Intrinsic attenuation from inhomogeneous waves in a dissipative anisotropic poroelastic medium

“…Major contribution comes from the intrinsic attenuation (Sams et al, 1997), which represents the internal frictions between the adjacent material grains not elastically bonded. The seismic data from sedimentary regions exhibit more intrinsic attenuation that can be explained through existing theoretical models (Pride et al, 2004). Analysis of seismic data suggests that hydrocarbon deposits are often associated with higher than usual Copyright c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.…”