  On-site measurements of water salinity (which can be directly evaluated from
the electrical conductivity) in deep-sea sediments is technically the primary
source of indirect information on the capacity of the marine deposits of
methane hydrates. We show the relation between the salinity (chlorinity)
profile and the hydrate volume in pores to be significantly affected by
non-Fickian contributions to the diffusion flux---the thermal diffusion and the
gravitational segregation---which have been previously ignored in the
literature on the subject and the analysis of surveys data. We provide amended
relations and utilize them for an analysis of field measurements for a real
hydrate deposit.
