SEISMIC AND ELECTRICAL-PROPERTIES OF UNCONSOLIDATED PERMAFROST

A model has been developed to relate the velocities of acoustic waves V//p and V//s in unconsolidated permafrost to the porosity and extent of freezing of the interstitial water. The permafrost is idealized as an assemblage of spherical quartz grains embedded in a matrix composed of spherical inclusions of water in ice. The wave-scattering theory of Kuster and Tokosoz is used to determine the effective elastic moduli, and hence the acoustic velocities. The model predicts V//p and V//s to be decreasing functions of both the porosity and the water-to-ice ratio. The theory has been applied to laboratory measurements of V//p and V//s in 31 permafrost samples from the North American Arctic. Although no direct measurements were made of the extent of freezing in these samples, the data are consistent with the predictions of the model. Electrical resistivity measurements on the permafrost samples have demonstrated their essentially resistive behavior. The ratio of resistivity of permafrost in its frozen state to that in its unfrozen state has been related to the extent of freezing in the samples.