Dynamic poroelasticity of thinly layered structures

Compressional seismic P-waves, propagating in poroelastic, fluid saturated, laminated sediments are strongly affected by the medium heterogeneity. Here, simple analytical expressions for the P-wave phase velocity and attenuation coefficient are derived. Both are functions of frequency and statistical medium parameters such as correlation lengths and variances. The theoretical results are compared with results from numerical simulations and show good agreement. In heterogeneous media, impedance fluctuations lead to poroelastic scattering; variations of the layer compressibilities cause inter-layer dow (a I-D macroscopic local flow); From the seismic frequency range (10-100 Hz) up to ultrasonic frequencies, attenuation due to heterogeneity is strongly enhanced compared to homogeneous Blot models. The new theory automatically includes different asymptotic approximations, such as poroelastic Backus averaging in the quasi-static and the no-flow limit, geometrical optics, and intermediate frequency ranges. (C) 1998 Elsevier Science Ltd. All rights reserved.