In order to quantify the concentrations of gas hydrate and free gas in the pore space, we use Biot-Geertsma-Smit equations to model the acoustic properties of different layers associated with the BSR. This approach models the different layers associated with the BSR (two solids -grains and clathrates- and two fluids –water and free gas-) including an explicit dependence on differential pressure and depth, and the effects of cementation by hydrate on shear modulus of the sediment matrix. The theory gives both compressional and shear wave velocities.

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The concentrations can be estimated by fitting the theoretical velocity to the experimental P-wave velocity. Supposing that positive anomalies are due only to the presence of hydrate, the discrepancies between the inverted velocity profile and the velocity for water-filled normally compacted marine sediments are interpreted as due to the presence of gas hydrate (where positive anomalies are present) and free gas (where negative anomalies are present).
We suppose four main distribution of free gas in the pore space:

1. uniform,
2. 50% uniform and 50% random,
3. patchy and
4. random.

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