Sound speed, attenuation, and reflection in gassy sediments.

A predictive model for acoustic dispersion and attenuation in gassy sediments is proposed. The model combines the linear solution for gas-bubble pulsations in a viscoelastic medium with corrected Biot equations involving gas-bubble pulsations. Numerical results for sound speed and attenuation are compared with predictions from Anderson and Hampton's model to demonstrate the advantages of the proposed model. The most important advantage of the current model is that it combines the dispersion regimes associated with gas-bubble pulsations and relative motion between the pore water and solid framework. The reflection coefficient at the water/gassy-sediment interface is derived based on the current model, and numerical results show that gas-bubble resonance can lead to the highest reflection. This model can also be used with a full acoustic inversion to estimate gas-bubble size distributions.