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1 National Oceanography Centre, European Way, Southampton SO14 3ZH, UK
2 Geological Survey of Norway (NGU), Tromsøkontoret, Polarmijløsenteret, 9296, Tromsø, Norway
* Corresponding author (e-mail: tmin{at}noc.soton.ac.uk)
Much of our knowledge on hydrate distribution in the subsurface comes from interpretations of remote seismic measurements. A key step in such interpretations is an effective medium theory that relates the seismic properties of a given sediment to its hydrate content. A variety of such theories have been developed; these theories generally give similar results if the same assumptions are made about the extent to which hydrate contributes to the load-bearing sediment frame. We have further developed and modified one such theory, the self-consistent approximation/differential effective medium approach, to incorporate additional empirical parameters describing the extent to which both the sediment matrix material (clay or quartz) and the hydrate are load-bearing. We find that a single choice of these parameters allows us to match well both P and S wave velocity measurements from both laboratory and in situ datasets, and that the inferred proportion of hydrate that is load-bearing varies approximately linearly with hydrate saturation. This proportion appears to decrease with increasing hydrate saturation for gas-rich laboratory environments, but increases with hydrate saturation when hydrate is formed from solution and for an in situ example.
