P波地震衰减的声子晶体效应

P-Wave Seismic Attenuation Due to Phononic Effects

研究储层中周期性复合介质的声带隙效应,给出一种地震波衰减机制.将周期分层孔隙介质模型看作一维声子晶体,采用改进的反射透射系数矩阵方法研究平面P波在其中传播时的声带隙现象.结果表明,当两种介质特征纵波速度不同时,在满足晶格厚度为平均纵波半波长整数倍的频率处,出现了一系列阻带,且低频阻带的宽度和衰减正比于该速度差异.不相溶流体的混合饱和与孔隙度的变化与颗粒和骨架参数的变化相比,其低频阻带具有更大的带宽和衰减.当晶格厚度为几米至几十米时,低频阻带处于地震频率范围内.

This paper deals with the acoustic band gaps in periodic composite materials, and gives out a new attenuation mechanism. Using the modified reflection and transmission matrices method, we considered the periodically stratified porous media as 1D phononic crystal, investigated the band gap properties of plane P-waves propagation. It is shown that there is a series of stop bands when the characteristic P-wave Velocities of the two media are different and the stop band frequencies satisfy that lattice thickness is integer multiples of average P-wave half-wavelength. The bandwidth and attenuation of the low-frequency stop band correspond to the difference of velocity. And with the same velocity difference, they are much greater when the difference is caused by porosity variations and partial saturation, compared with grain- and frame-parameter variations. When the lattice thickness is in the magnitude of meters or decades meters, the low-frequency stop band is within the seismic band of frequencies.