Field work

The distinct geophysical properties of permafrost materials are closely associated with ice content. Hence most geophysical properties (e.g. electrical resistivity and seismoacoustic velocities) vary with temperature (below 0°C) as well as the chemical composition of porewater.

Geophysical techniques are used in permafrost areas to 1) map distribution of ice-bearing materials, and 2) to assess geophysical properties associated with soil type and ice content. Such geotechnical applications directed towards oil and gas pipeline route selection and placement of gravity structures include: mapping ice-bearing soils in discontinuous permafrost routes, mapping of "talik" (thaw) zones and "cryopegs" (saline unfrozen zones) in continuous permafrost, estimation of ice-content (including massive ice-lensing), and identification and structural mapping of sub-seabottom permafrost.

The Terrain Geophysics Section has experience in most types of geophysical applications (see Scott et al., 1990) in permafrost which involve such techniques as: seismic refraction, seismic reflection, electromagnetics, electrical resistivity, and borehole logging. Given below are some examples of the application of geophysical techniques to permafrost problems from recent R&D work by the Terrain Geophysics section.

• Sub-seabottom permafrost
• Mapping ice content
• Seismic reflections from the permafrost zone (shear-wave)
• Mapping contaminant plumes