DYNAMIC POROELASTICITY OF THINLY LAYERED STRUCTURES

Compressional seismic P-waves, propagating in poroelastic, fluid satur ated, laminated sediments are strongly affected by the medium heteroge neity. Here, simple analytical expressions for the P-wave phase veloci ty and attenuation coefficient are derived. Both are functions of freq uency and statistical medium parameters such as correlation lengths an d variances. The theoretical results are compared with results from nu merical simulations and show good agreement. In heterogeneous media, i mpedance fluctuations lead to poroelastic scattering; variations of th e layer compressibilities cause inter-layer dow (a I-D macroscopic loc al flow); From the seismic frequency range (10-100 Hz) up to ultrasoni c frequencies, attenuation due to heterogeneity is strongly enhanced c ompared to homogeneous Blot models. The new theory automatically inclu des different asymptotic approximations, such as poroelastic Backus av eraging in the quasi-static and the no-flow limit, geometrical optics, and intermediate frequency ranges. (C) 1998 Elsevier Science Ltd. All rights reserved.