Seismic and ultrasonic velocities in permafrost

• Published in: Geophysical Prospecting
• Main Authors: Carcione, José M., Seriani, Géza
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1998
• Subjects: Ice; permafrost
• Online Access: http://dx.doi.org/10.1046/j.1365-2478.1998.1000333.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2478.1998.1000333.x; https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2478.1998.1000333.x

We calculate the compressional‐ and shear‐wave velocities of permafrost as a function of unfrozen water content and temperature. Unlike previous theories based on simple slowness and/or moduli averaging or two‐phase models, we use a Biot‐type three‐phase theory that considers the existence of two solids (solid and ice matrices) and a liquid (unfrozen water). The compressional velocity for unconsolidated sediments obtained with this theory is close to the velocity computed with Wood's model, since Biot's theory involves a Wood averaging of the moduli of the single constituents. Moreover, the model gives lower velocities than the well‐known slowness averaging theory (Wyllie's equation). For consolidated Berea sandstone, the theory underestimates the value of the compressional velocity below 0°C. Computing the average bulk moduli by slowness averaging the ice and solid phases and Wood averaging the intermediate moduli with the liquid phase yields a fairly good fit of the experimental data. The proportion of unfrozen water and temperature are closely related. Fitting the wave velocity at a given temperature allows the prediction of the velocity at the whole range of temperatures, provided that the average pore radius and its standard deviation are known.