Methane hydrates, which can be described as being frozen methane gas, form at the transition of methane through a pressure-temperature dependent phase-boundary. Since the required pressure-temperature conditions usually occur within several hundred meters beneath the seafloor, the sediments above and below the hydrate-bearing sediments can be assumed to be unconsolidated, subjected only to hydrostatic pressure. Depending on the origin of the methane necessary for the hydrate formation, the hydrate-bearing sediments might be underlain by either gas-saturated sediments Kvenvolden and Barnard (1983a) or brine-saturated sediments in which the methane saturation does not exceed the saturation solubility of water Hyndman and Davis (1992). Several different ways in which the methane then solidifies into hydrate after the transition through the required phase boundary can be imagined. One possibility is that the hydrates formation cements the rock grains together, either by hydrate deposition at the grain contacts or by uniform hydrate deposition on the grain surface, thus considerably increasing the stiffness of the structure Dvorkin and Nur (1993). Another possibility might be that the hydrate forms randomly in the pore space without having a direct influence on the rock matrix.