介观尺度不均匀对反射系数的影响
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摘要
介观尺度介于地震波长尺度及孔隙颗粒尺度间,地震波传过介观尺度不均匀介质时层间的应力差会引起流体流动,摩擦力使动能向热能转化产生衰减。White层流模型[1]是介观尺度的不饱和模型,该模型中两种饱和介质薄层周期交替。计算了地震频带上纵波穿过饱气层、饱水层周期出现模型的相速度Vp(ω)和品质因子Q(ω);建立无衰减对比模型以计算对反射系数的影响。结果显示纵波入射不饱和层时,反射系数随频率变化明显,尤其是在低频处的衰减峰值附近。
Mesoscopic scale is larger than grain and smaller than wavelength.The pressure difference between different fluids induced fluid flow when seismic wave penetrate the mesoscopic inhomogeneous media. The cause of attenuation is the friction which transfer kinetic energy to heat. White's layered fluid model is a kind of mesoscopic-scale partially saturated model with two periodically alternating saturated layers. This paper computes the phase velocity Vp(ω)and quality factor Q(ω)of water-gas saturation layered model. A comparison is modeled to research the attenuation effect on reflection coefficient. The result show that the reflection coefficient of unsaturated layer changes significantly with frequency, especially near peak frequency of attenuation.
Mesoscopic scale is larger than grain and smaller than wavelength.The pressure difference between different fluids induced fluid flow when seismic wave penetrate the mesoscopic inhomogeneous media. The cause of attenuation is the friction which transfer kinetic energy to heat. White's layered fluid model is a kind of mesoscopic-scale partially saturated model with two periodically alternating saturated layers. This paper computes the phase velocity Vp(ω)and quality factor Q(ω)of water-gas saturation layered model. A comparison is modeled to research the attenuation effect on reflection coefficient. The result show that the reflection coefficient of unsaturated layer changes significantly with frequency, especially near peak frequency of attenuation.
引文
[1]White,J.E.,N.G.Mikhaylova,and F.M.Lyakhovitskiy,1975,Low-frequency seismic waves in fluid saturated layered rocks:Izvestiya,Academy of Sciences,USSR.Physics of the Solid Earth,11,654-659.
[2]Carcione,J.E.M.and S.Picotti,P-wave seismic attenuation by slow-wave diffusion:Effects of inhomogeneous rock properties[J].Geophysics,2006,71(3):1-8.
[3]Dutta,N.C.,and A.J.Seriff,1979,On White's model of attenuation in rocks with partial saturation:Geophysics,44,1806-1812.
[4]Muller,T.M.and B.Gurevich,Wave-induced fluid flow in random porous media:Attenuation and dispersion of elastic waves[J].The Journal of the Acoustical Society of America,2005,117:2732.
[5]Brekhovskikh,L.M.,1980,Waves in layered media:Academic Press,Inc.
[2]Carcione,J.E.M.and S.Picotti,P-wave seismic attenuation by slow-wave diffusion:Effects of inhomogeneous rock properties[J].Geophysics,2006,71(3):1-8.
[3]Dutta,N.C.,and A.J.Seriff,1979,On White's model of attenuation in rocks with partial saturation:Geophysics,44,1806-1812.
[4]Muller,T.M.and B.Gurevich,Wave-induced fluid flow in random porous media:Attenuation and dispersion of elastic waves[J].The Journal of the Acoustical Society of America,2005,117:2732.
[5]Brekhovskikh,L.M.,1980,Waves in layered media:Academic Press,Inc.