Modeling in situ effects of gas hydrates on sediment properties using estimated hydrate properties has many practical applications. Until recently, reliable measurements of such properties were hampered by technical problems, such as the difficulty of making pure materials. These difficulties have been largely overcome using methods developed over the last 5 years, including a simple method for making >99% pure sI and sII hydrates. Preservation of such material by cooling to 77 K has made possible accurate measurements of thermal diffusivity and the ductile rheology of compacted sI methane hydrate possible. By integrating hydraulic compaction and sensors into the synthesis vessel, reliable measurements of wavespeeds (Vp and Vs) and thermal conductivity (k) have been made on compacted sI and sII hydrates. Standout results include discovering hydrocarbon hydrate properties are generally very different from those of ice. For example, sI methane hydrate is 20 to 50 times stronger than ice and has a thermal conductivity less than 20% that of ice.