Occurrence and acoustical significance of natural gas hydrates in marine sediments

Abstract

The current knowledge of natural gas hydrates in marine sediments is reviewed. The Chemical structure, occurrence in nature, conditions of formation and acoustic properties of natural gas hydrates are discussed. Conditions suitable for the formation of this icelike crystalline structure, which traps the gas molecule within it, are found over 90% of the ocean floor. The hydrate structure can greatly increase compressional sound velocity and alter shear velocity and absorption processes from those expected for typical marine sediment types. The potential impact of hydrates on underwater acoustics is demonstrated through computations of bottom reflection loss for hypothetical subbottom structures containing hydrate zones. [Work sponsored by Naval Oceanographic Research and Development Activity.]