ABSTRACT
Natural gas and water combine to form an ice-like substance called a gas hydrate under certain conditions of temperature and pressure. Hydrates of natural gases occur in marine sediments to depths of several hundreds of feet below the sea floor. The base of the layer in which the hydrates are stable occurs at a local phase boundary that is dominantly influenced by a downward increase in temperature. The Spectral Analysis of Surface Waves (SASW) method is a nonintrusive seismic method which has been successfully used on land to determine shear modulus profiles of geotechnical sites. The SASW method employs seismic waves of the Rayleigh type, which are mainly influenced by the shear stiffness of the material through which the wave propagates. Wave motion within a uniform medium can be described by two kinds of stress waves: compression waves and shear waves.
