Connecting poro- and visco-elastic acoustic models of marine sediments: Salinity, force chains, creep, and permeability

Abstract

A poro-elastic model for both sandy and muddy marine sediments is used to derive a visco-elastic approximation, and compared to the existing measurements of wave speeds, attenuations, and reflection. The poro-elastic model is the modified, corrected, Revil, extended Biot (mCREB) model. Its derivation, which includes a force chain approximation and a creep mechanism, is reviewed and equations for implementation are provided. It fits the existing measurements over a broad range of frequencies from a few Hertz to almost a megaHertz. Salinity is essential to the poro-elastic behavior of mud. A visco-elastic approximation is derived, based on the zero permeability condition. It is a simpler model with fewer input parameters, and practically identical to the popular viscous grain shearing (VGS) model, although their derivations are very different. Comparisons between the measurements, the poro-elastic model, and its visco-elastic approximation are made in order to identify the circumstances in which the latter may be used. Generally, the visco-elastic approximation may be used for frequencies below 1 kHz in mud and sand. At higher frequencies, poro-elastic effects dominate rendering the visco-elastic approximation inaccurate.